In this article, we go over 10 methods to clean out condensate drain lines and traps on air conditioning systems! The condensate drain line is responsible for removing the water that is extracted from the indoor air (humidity) during air conditioning mode. Over time, the drain trap and/or line can become clogged with dirt, dust, bio-growth, and other debris. When this happens, the water may back up into the system, overflowing out of the primary drain pan and causing damage to the system and/or building. Let's discuss the fastest methods for clearing these lines/traps. To prepare for cleaning, the system's power must first be switched off so that air is not being pushed or pulled through the drain line/trap. Also, if you have access to the trap, remember to fill it back up with water when you are done and cap off any service access openings when complete. Method #1: Using a Shop Vac to Evacuate The Drain Line at the Outside Location Simply connect the wet/dry vacuum hose to the end of the drain line outside and turn on the vacuum. The suction will help remove any blockages or debris in the line. To better clean out the lines, add water at the indoor unit primary pan or the line's service access location while doing this!
Method #2: Blowing out the Condensate Line with 30 PSI of Compressed Air using an Extended Tip.
To get a better seal inside the tubing, wrap the end of the extended tip with electrical tape. Then, place the tip down into the trap and apply the compressed air to blow out the debris. Make sure to not apply excessive pressure because this could cause a pipe joint to separate and leak. When finished, fill the trap back up with water and replace the cap.
Method #3: Clear the Trap Using a Brush
Remove the caps on both ends of the condensate trap. Pull the brush through the trap to break up clogs and extract debris. When finished, fill the trap back up with water and replace the caps. Method #4: Clearing The Drain Line at a Horizontal Tee With A Shop Vacuum
When there is a horizontal access tee, use a 1/2" CPVC 90 ° fitting with a section of CPVC pipe attached to a 3/4" PVC bushing, to access the inner pipe. The 3/4" bushing typically fits into the shop vac's hose end. This assembly can be used to blow or suck out debris inside the horizontal section of pipe. Remember to fill the trap with water and replace any service caps when complete.
Method #5: Vacuum the Trap Using a Shop Vac Hose with a Section of CPVC Pipe Attached to the End.
Simply connect the 3/4" to 1/2" pipe to the end of the shop vac and insert it into the condensate trap. Remember, attaching electrical tape to increase the diameter of the 1/2" CPVC pipe will allow it to seal better when inserted into the trap. Turn on the shop vac. Remember to fill the trap with water and replace the service caps when complete.
Method #6: Blow Out the Condensate Trap Using the Shop Vacuum
A shop vac can be used to blow out the trap instead of sucking out the debris. In this scenario, move the vacuum hose end to the outlet of the shop vac instead of at the inlet. Then insert the 1/2" CPVC pipe into the trap and turn on the vacuum. Remember to fill the trap with water and replace the service caps when complete. Method #7: Blowing Out a Condensate Trap With Clear Vinyl Tubing Only

In the absence of an accessible electrical outlet or pressurization device, you can use a clear vinyl tube with electrical tape on the end inserted into the trap. At the exposed open end of the clear vinyl tube, apply force through the tubing with a large breath.
Method #8: Applying 30 PSI of Nitrogen Through a Cone End to Blow Out The Condensate Trap.
A nitrogen tank can act as an alternative to compressed air. Attach a hose and air gun to the nitrogen regulator and set the secondary regulator to 30 PSI. Apply the air gun end to the open section of pipe and allow the nitrogen to blow out the clog. When finished, fill the trap back up with water and replace the cap.
Method #9: Applying 30 PSI of Nitrogen Through an Extension Tube to Blow Out the Condensate Trap.
Attach a hose and air gun to the nitrogen regulator and set the secondary regulator to 30 PSI. Add the extension tube with electrical tape on the end to the air gun. Put the extension tube down into the trap and allow the nitrogen to blow out the clog. When finished, fill the trap back up with water and replace the cap. Method #10: Using Pressurized Air Through a Flexible Extension Hose
To get to hard to reach places, a small flexible extension hose can be added to the air gun. Fish the flexible hose end (poly tube end) into the open section of the condensate drain line. Cover the remainder of the opening and then apply the air/nitrogen pressure through the drain line. This method can be used when there is no service access cap or when the only access is the primary drain pan outlet. A Quick Note: Method #1 is a preferred method because not only is the clog removed, but the entire drain line can be flushed by adding water into the indoor service access cap or drain pan. Always add water back into the trap when complete! This stops any air from being pulled or pushed through the drain line and allows water accumulating in the primary pan to drain out properly.
Want to see these methods in action? Check out our YouTube Short! https://youtube.com/shorts/MkHgXlt9p8M

Learn more about the function of the condensate trap by watching our videos below!

Check out our free Quizzes to test your knowledge here!

Check out our Free Calculators here!

If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book .

Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store

Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Follow us on Instagram! Published: 5/10/23 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 17 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel

On a mini-split ductless system, two copper tubes are needed to transport the refrigerant. These copper tubes are referred to as the line set and they connect the indoor head unit to the outdoor heat pump or condensing unit. Two flare connections are needed at the indoor head unit and two flare connections are needed at the outdoor mini-split unit. Things to consider: · A standard system has four flare connections while a multi-zone system has more flare connections for the additional indoor head units. · The pressure of the refrigerant in the system will be anywhere from approximately 100-400 PSI depending on whether the unit is in heating or air conditioning mode. Therefore, it is essential to have all the flare connections correctly sealed so that refrigerant does not leak out of the system. Listed below are the ten most common reasons mini-split flares may leak. Problem #1 : The Flare Size is too Small · At the end of the copper tube, the surface on the flare face must be big enough to take up the full amount of space inside the flare nut. The reason for this is so that the tube's flare face entirely covers over the seat of the flare adapter. This will give you the best chance at sealing this connection point. · If the tube flare is not very wide, it will only cover half of the connection point and will barely seal the joint. · The flare may accidentally be made too small if the flare block is not tight enough. If the block is not tight enough, the copper tube will slide while you are trying to make the flare. Use the rod that comes with the flare block to tighten the block as hand tightening may not be sufficient. Problem #2 : Over-Tightening the Flare Connection · This could be caused by using adjustable wrenches that are too large. If the wrenches are too large, you will not feel when the joint is tight and you will easily over-tighten the joint. · Over-tightening can cause the threads of the flare nut and adapter to become stripped/dethreaded. · This causes the flare face inside the nut to be crushed or cracked. · Over-tightening may cause the tubing inside the flare nut to spin, which scratches the flare seat or flare face so that it no longer has a good seal. · Always use a torque wrench when connecting mini-split lines. The mini-split manufacturer’s installation literature should list the correct amount of foot-pounds that the connections need to be tightened to. Each manufacturer's required foot-pounds may be different. Eight Head Mini-Split Torque Wrench: https://amzn.to/2NRR68Q Problem #3 : The Cone is Scarring up the Flares · This may be due to the fact that refrigerant oil was not added to the cone of the tool before flaring the copper. · It could be because the cone itself is bad or rough. · An eccentric flaring tool would likely be the best tool to avoid scarring the flare face. This is because the cone of this tool has the least amount of surface contact while forming the flare out of any tool. Eccentric flaring tool: https://amzn.to/2OBxGlM Problem #4 : No Refrigerant Oil on the Flare Face · A small amount of refrigerant oil or Nylog Blue (which is compatible with all refrigerants) should be applied to the flare face before tightening the connection. · Make sure that oil or Nylog does not get onto the threads of the flare as this will act like a lubricant. This may cause you to accidentally over-tighten the flare or to strip the threads on the nut or the flare adapter. · You don’t want to get the Nylog Blue inside the tubing as it may clog strainers if it is pushed into the system by the refrigerant. · Carry a small container of POE oil, PVE oil, mineral oil, or other comparable oils with you if you choose not to use Nylog. Small Nylog Blue: https://amzn.to/2MLJcch Problem #5 : An Incorrect Flare Nut is Being Used · When working on a mini-split system, be sure to only use flares nuts that have been specifically manufactured for mini-split ductless units. · A flare nut could crack over time if it is not designed to handle the pressure of R-410A or other refrigerants. · A flare nut could crack if it is not designed to be exposed to the outdoor environment. Problem #6 : A Scratch on the Flare Face or Flare Adapter · If there is a scratch on either the flare face or the flare seat of the adapter, it may be enough to allow refrigerant to leak out of the system. Problem #7 : Preparation of the Copper Tubing · If the copper tubing is squished while it is being cut, it usually cannot be used no matter how much you deburr the inside of the tube or re-round the outside of the tube. · Using a stick reamer or a unibit to ream the hole in the end of the copper tubing may not be a good idea. It could result in the inside of the tube being scarred, which you don’t want to happen. This could cause your flare face to be scarred before you even make the flare! · Deburr the hole at the end of the copper tubing well before starting to flare. Problem #8 : Using an Improper Flaring Tool · The correct flaring angle to use for HVAC and plumbing is one with a 45 degree flare. There are flaring tools out there that have different angles such as 37 degrees, which you don't want for flaring refrigerant tubing. · A standard flaring tool, a process flaring tool, or an eccentric flaring tool will create the correct 45 degree angle needed for a refrigerant tube flare. · A spin flare will create a smaller angle flare but while the copper tube is still hot, it can be tightened to the flare adapter which will stretch the flare face to 45 degrees. Spin Flares: https://amzn.to/31BCs8Z Here is a video I made using spin flaring and spin swaging bits: https://youtu.be/iFOTxT1qkLk Problem #9 : Improperly Torqued Flares · Read the manufacturer’s literature to learn the recommended foot-pound torque. Some manufacturers data will only be in metric. Make sure to have a torque wrench with heads that include standard and metric. Eight head torque wrench: https://amzn.to/2NRR68Q · Remember that the torque value may vary from manufacturer to manufacturer and it will vary depending on the size of the copper tube, flare adapter, and flare nut size. · An adjustable head torque wrench can be used when working on systems with many flare nut sizes. This allows you to speedily adjust your torque wrench. Adjustable head torque wrench: https://amzn.to/3bSJrPs Problem #10 : The Pressure Test · If you pressure test the system at a low PSI, a leak may not show up until you run the system in heating mode. · When using a compound manifold gauge set, you may have to let the pressure test sit on there longer because the incremental changes in a compound gauge are very small. · A leak shows up quicker when using a digital manifold gauge compared to a compound manifold gauge set because the digital display indicates changes in tenths of a PSI. · You want to pressure test the system below the max design pressure of the unit. Follow the manufacturer’s installation literature for pressure testing so that you do not over-pressurize a system. · If a leak is detected, use a non-corrosive bubble leak detector on the exposed joints in order to find the leak or use an ultrasonic leak detector. Bubble leak detector spray bottle: https://amzn.to/2Zm0TJF 8-ounce bubble leak detector with dabber: https://amzn.to/2TqKXSx Ultrasonic leak detector: https://amzn.to/2XlLTce · Do a pressure test before doing the vacuum procedure, otherwise if there is a leak, you will pull in the humid air surrounding the outside of the leak spot into the tubing. · When performing a vacuum, pull the vacuum down below 500 microns and perform a standing vacuum test. Try to target at least 200-300 microns while the vacuum pump is running, before performing the standing vacuum test. Here is a video on vacuuming a mini-split ductless unit and breaking the vacuum with refrigerant from the bottle: https://youtu.be/k9uohbYDuRs Here is a video showing the 10 reasons why mini-split flares may leak: https://youtu.be/iLTMlIT6Qvg Check out our Quizzes to test your knowledge here ! Follow us on Facebook for Quick Tips and Updates here !
Published: 5/20/2020 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 15 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel & https://www.facebook.com/acservicetech/

This article covers the 10 most common reasons the blower fan does not turn on! A blower motor may be installed in a forced air gas or oil furnace, air handler, or packaged unit. There are multiple reasons why the motor won't start and these are based on the type of unit, controls, and the blower motor type. Problem # 1: Capacitor When an HVAC unit is equipped with a PSC (Permanent Split Capacitor) blower fan, a capacitor is required to both start and run the motor. The capacitor's job is to store and then discharge electrical energy in order to create an artificial phase of electricity for the blower motor power supply. Testing the capacitor: First, turn the main power switch to the unit to the off position. Verify the power is off with a multimeter. Remove the electrical wires from the capacitor. Temporarily mount a 2K ohm bleed-resistor onto the capacitor to bleed off any residual voltage. Leave the bleed resistor on for 4-5 seconds (see first photo below) . A multimeter that is capable of reading MFD (microfarads) should be connected to the capacitor by mounting one probe on one terminal and the other multimeter probe to the second terminal (see second photo below) . Make sure the multimeter function is set on MFD and keep the probes on the capacitor for 10-20 seconds to get an accurate measurement. If the MFD reading displayed on the multimeter is within + or - 6% of the MFD rating on the side of the capacitor, it is still good. If it is outside this range, the capacitor is bad. The second photo below shows a MFD reading of .626 when it should be 10MFD so this capacitor is bad. Problem # 2: Blower Motor After a bad capacitor has been replaced, the blower motor may turn on intermittently and have a burning smell. This occurs because the blower motor sustained damage due to the bad capacitor. When the bad capacitor is in the unit, the high temperature thermal limit prevents the windings from opening up or shorting out when the rotor is not spinning. However, the resin insulation on the motor windings melt down and degrade. This results in the motor overheating and failing even after a good capacitor is installed. This failure may occur with thirty minutes of the new capacitor being installed or even a couple days after the new capacitor is installed. It is difficult to tell if the blower motor has sustained damage due to a bad capacitor because a standard digital multimeter does not have the ability to do a deep enough test. A megohmmeter (also known as a megger) may be needed. NOTE: Any time you have a bad capacitor, be ready to also replace the blower motor. Problem # 3: Blower Motor Electrical Windings If the blower motor windings have opened up, shorted together, or shorted to ground, the motor will not start. This can be tested with a digital multimeter while the power is off to the unit. Be sure the blower motor is cool before testing the windings because if the motor is overheated, the internal thermal limit switch on the common wire may be open. This may fool you into thinking the motor windings are burnt open/apart when in fact, the motor just needs time to cool down before testing. Use a multimeter to check the resistance values between each of the wires leading to the blower motor. To do this, make sure the power is off and the wires are disconnected from the control board (see photo above). Below is an example of a 120v PSC (permanent split capacitor) blower motor from a gas furnace. common (white) and black (highest fan speed)= lowest resistance value common (white) and blue (middle fan speed)= medium resistance value common (white) and red (lowest fan speed)= highest resistance value Leave the probe in the common wire while you check each of the capacitor leads (see photo below) . When testing between the common and one of the capacitor leads, the resistance values may be 4-6 times higher than the highest of the motor speed wire's resistance. When testing between the common and the other capacitor lead, the resistance value may match or be close to the value of one of the speed wires such as the lowest speed wire. At this point, if the resistance value measured from the common to each of the capacitor leads are intact and does not measure 0.L, this means all the blower motor wires within the motor are intact. There are no open shorts because we testing the speed wires in the previous steps. Next, check from one of the wires to the ground frame (the blower motor casing). The multimeter should read 0.L (see photo below) . NOTE: If the reading to ground is anything other than 0.L to ground, it means one of the windings is shorted onto the ground frame and the blower motor is bad. Problem # 4: Blower Motor Bearings With the power off to the unit, reach in and grab the center of the blower motor (see photo below) . Spin it to see how easily it turns. Wiggle it to see if it falls into a groove or indentation. If the motor does not turn easy, or the it wiggles while spinning, there may be a bad bearing. Problem # 5: ECM Blower Motor Module If a unit has an ECM (electronically commutated motor) blower, these motors have high voltage power any time the unit is powered. Then the motor module is waiting for a low voltage signal to know when it should turn on and at what speed. If the ECM motor has a low voltage signal along with high voltage power, but the motor isn't turning on, the problem most likely is a bad module. Use a multimeter to determine if there is high voltage power to the motor (see photo below) . To visually inspect the motor module, first, turn off the power to the unit and disconnect the wires attaching to the module. Loosen the screws on the end of the bell or module housing. Remove the screws and pull the module away from the end of the motor slightly. Next, disconnect the three wire connection from the module to the motor (see photo below) . Inspect the inside of the module both visually and with your nose to determine if any component, such as a capacitor or the current limiter, is cracked or burnt. If a current limiter is bad (see photo below) , technically, you can replace the bad component with one of the same ratings using a soldering gun. This could be done instead of replacing the module. However, it is best to replace the module. Problem # 6: Bad Control Board If the unit has an ECM motor, the control board is designed to communicate with the ecm blower motor. These are referred to as communicating control boards. It is possible that the control board is not sending the communication signal to the motor. However, first test the blower motor using a TecMate PRO to see if the problem is with the motor (see photo below ) . If the blower motor turns on when it is given a signal via the TecMate PRO, this indicates that the motor is not the problem. The problem could be loose wiring at the connections or a bad control board. Remember to check for a thermostat signal at the control board calling for the blower motor to turn on. If the multimeter measures 24v from G to C terminals, the control board should tell the blower motor module to turn the blower motor on. If the motor isn't the issue, then the problem is either with the wiring or the control board. Make sure each individual wire is firmly in place in the control board and in the motor. Make sure the motor has 24v from the G to C terminals at the control board. A PSC motor uses a lower tech control board (see photo below) . Any time there is 24 volts on the G terminal, the Com (Common Connection Point) terminal and the NO (Normally Open) terminal in the black box should connect. If these contacts within the black box do not touch, this is probably due to the contacts being pitted and burnt. The main reason these type of control boards fail is the switching part of the relay. The relay contacts melt, pit, and burn due to high current crossing them over time. This relay is used to send high voltage power to the PSC blower motor. Save 8% on any purchases from TruTechToolS.com witH code: acservicetech Problem # 7: Thermostat Face At the thermostat, if the fan is in the "On" position (see photo below) , but the blower motor is not turning on and there isn't a common wire connected to the thermostat, the batteries may be drained of power and need to be replaced. ( NOTE : Not all thermostat faces show a "Batteries Low or Replace Batteries" message. Therefore, replace the batteries on a regular schedule, such as every six months.) If the batteries are good and/or the common wire is attached, but the fan is not turning on, further testing may need to be performed. Test the thermostat wires at the thermostat back plate to bypass the thermostat face (see photo below) . Connect two jumper wires from... r to g in order to turn on the fan r to w in order to turn on the heat r to y in order to turn on the air conditioning system If after connecting R to G, the fan now turns on, the thermostat face was the issue. Replace the thermostat face. Problem # 8: Power Off to the Furnace or Air Handler Make sure the power switch to the furnace or air handler is on. If the thermostat is lit, the assumption is that the power to the unit is on. However, the thermostat may only be lit because it has batteries and is not hard wired. Make sure the door switch is pressed in tightly. If the LED is lit on the control board, this means there is power to the unit. However, if an error code is being displayed there is an issue that needs to resolved which may have locked out the unit from operating. Look up the error code on the unit's shroud to see what the problem is (see photo below) . If the control board doesn't have an LED, use a multimeter to see if you have power on the control board between the high voltage Common/Neutral and L1 (see photo below) . Problem # 9: Thermostat Wiring There may an issue with the thermostat wiring from where it runs in the building to the indoor unit. An animal may have chewed into the wire, or the wire may have been squished by a wire staple during installation (see photo below) . Rather than staple a wire directly onto the wood, hammer it part way in and zip tie the wire to it (see photo below) . You can bypass the thermostat and the thermostat wiring by jumping from r to g at the control board (see photo below) to see if the blower motor turns on. If the blower motor turns on, this indicates that the problem is not with the control board or the unit. The issue is with the thermostat wire (if you've already troubleshot the thermostat itself and determined it is not the problem). Problem #10: Ductwork The problem may be due to a clog in, or a collapse of, the ductwork (see photo below) . The blower motor may be running but if the duct has collapsed in the return or rotted open in the supply, no moving air is felt at the registers. Looking for some examples of troubleshooting a Furnace, AC or Heat Pump Blower? Check out our video below! "HVAC Blower Motor FAN WON'T TURN ON, NOT WORKING! Top 10 Reasons/Problems! Heat and AC!" Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Tools that we use: www.amazon.com/shop/acservicetech Tools that we use: www.trutechtools.com 8% off coupon code "acservicetech"
Follow us on Facebook for Quick Tips and Updates here! Follow us on Instagram for Quick Tips and Updates here! Published: 7/27/2022 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 17 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel

In this HVAC training article, I discuss 20 AIRFLOW Problems that you may find on ducted gas furnaces, air conditioners, heat pumps, air handlers, and packaged units. Some problems happen over time due to lack of maintenance while others may have occurred during the initial installation. Low air flow is a big deal, so it is important to figure out what is causing this issue. For a furnace it could overheat. For an air conditioning system, the evaporator coil could freeze. If the problem isn’t that bad, you can still have longer run times, lower capacity and lower electrical efficiency. The system's lifespan can also be reduced. Let's be aware of what these problems are in order to fix them. Below, I discuss each of the 20 problems. Problem #1 Dirty Indoor Air Filter It is important to change out the air filters, so that they don’t get clogged with dust. Keep in mind, while most systems have one air filter, some systems may have multiple filters. You need to look at the interior walls and the ceiling in each room of the building to see if there are multiple FRAG's (filter return air grilles) and change the filters in each one. Remember, you could find more than one filter in a row in the main return duct. This usually happens on accident when the occupant doesn't know the location of the original filter and adds another because they think that the system is not currently equipped with one. Take your time, investigate, look for filter racks cut into the duct, in the return near the furnace/air handler, inside the unit, and at the grilles. After you initially investigate, you will know for future service. Problem #2 Air Handling Cabinet – Loose Insulation This area may be overlooked. Inspect the inside of the air handler, furnace, or packaged unit cabinet. The glue that holds the insulation in place may come undone. This happens more often then you may think. Be aware because when the blower motor shuts off, the insulation may fall back into it's normal spot but while the system runs, the insulation sticks to the side of the blower motor squirrel cage and restricts the airflow. Problem #3 Dirty Blower Wheel When doing a preventative maintenance, clean off the blower wheel fins inside the blower squirrel cage. Make sure that they are as smooth as possible. You can use a brush and shop vac to clean them off. The blower wheel becomes less effective at moving air as dust accumulates on the blower wheel. Problem #4 Dip Switches Never Set Properly If the airflow dip switches or pin connector on the main control board were never set properly, this will cause an incorrect airflow speed. The system's control board determines what speed the ECM blower motor should run at. Set the airflow speed based on the unit's BTU/HR heat removal or heat gain capacity. For air conditioning, refer to the outdoor unit rating plate for the BTU/HR size. Problem #5 Find The Supply Registers You will need to find all of the supply registers. This may require you to move around furniture etc. to ensure that they are all exposed and fully open. Problem #6 Return Grill and Supply Registers: Too Small and/or Not Enough Be sure to consider the size and number of the return grilles and supply registers for the system size. This is an initial design mistake that we find when servicing existing units. Problem #7 Filter Is Too Restrictive If the air filter is too restrictive, you can go with a less restrictive type. The filter manufacturer should have the pressure drop noted on either the packaging or in the service literature. The higher the pressure drop, the more restrictive to the airflow. There are different types of filters available with varying pressure drops. A pleated filter that is 3” or 4” wide may be a good choice if there is room for a wide filter rack to be installed. Wide filters are often used to lower the pressure drop while still filtering the air because more surface area equals less restriction. Problem #8 Secondary Heat Exchanger Clogged With Dust When noticing low airflow, the issue could be the secondary heat exchanger on a 90% efficient furnace. This is the first coil downstream of the blower motor that could get clogged with dust and block the airflow. Problem #9 Airflow Going Unchecked It is important to measure the airflow going across the coil. You can do this by using the Temp Rise formula, a Hot Wire Anemometer, or by measuring the total external static pressure and comparing it to the manufacturer's guidelines. Check out these videos related to this process using the Temp Rise Formula , External Static Pressure and Hot Wire Anemometer . Problem #10 Supply Flex Not Installed Properly On The Collar Look at the supply flexes to see how they are installed. Issues with incorrect installation will cause it to fall off over time, especially if it gets kicked in the attic or there are no hangers holding it in place in the crawl space. The flex could also fall off due to it's weight over time or as a result of the air pressure in the duct. The supply air could be flowing right into the crawl space. Make sure flexes are installed properly and tightly onto the collar with zip ties, screws and/or tape. Problem #11 Clogged Evaporator Coil The evaporator coil could be clogged with dust. This happens as a result of not having a filter installed on the system. This is often an overlooked airflow blockage because it is not easily seen. A significant static pressure drop across the indoor evaporator coil signals a clogged coil. Problem #12 Frozen Evaporator Coil This can happen due to 1 of the 3 following issues: (1) Low refrigerant charge (2) Liquid line restriction (3) Low indoor air flow With a frozen coil, the air cannot pass through to the supply ducts. We have an additional article which covers “Troubleshooting an Air Conditioning System with a Frozen Evaporator” . This article differentiates between a low refrigerant charge, low airflow and a liquid line restriction. Problem #13 Acoustical Liner Blocking Air Flow A duct that has internal acoustical liner may have some of the liner pulled off of the interior wall, partially blocking the duct. Liner is glued and buttoned in place. If the glue or buttons let go, the liner can get sucked back into return and block the airflow. The acoustical liner may have been used as duct insulation instead of installing insulation on the outside of the duct. The real use of an acoustical liner is to quiet the noise in a short return duct. Make sure that the interior of the duct is clear of obstructions. Problem #14 Leaky Joints In Duct Work Check to make sure that all joints are sealed up well. We don’t recommend using tape directly on the metal because the metal has oil on it so the tape will not seal properly. Seal the joints with Duct Sealant (Mastic). This can be purchased in a caulk tube or tub. We have links below: Duct Mastic in the Caulk Tube: https://amzn.to/3fc1pzm Duct Mastic Tube: https://amzn.to/2SrIGpU Problem #15 Improper Size for Supply / Return Trunk Ducts The internal duct size and static pressure may not be sufficient to allow the correct amount of airflow needed across the indoor evaporator coil. In order to find the BTU/HR size of the outdoor unit, look at the rating plate of the outdoor unit. The BTU size is usually incorporated into the model number. Design or improve the existing duct work to accommodate the BTU size by using Manual D for residential systems. Problem #16 Squished Duct Look over the ductwork to locate improperly installed and squished ducts. Some ducts may not be squished but have too many turns or be too long. In this case, airflow will not make it to the supply register at full capacity. Problem #17 Too Many 90 Degree Turns In the Main Trunk Duct Keep turns to a minimum when designing ducts. Remember every time you add a 90 degree turn, it isn’t just the length of the turn that is added to the total length of the duct. The turn is adding a significant equivalent length of duct to the system. Problem #18 Supply Trunk Duct Is Reduced Too Far too Soon I often find that the main trunk duct is reduced too small in size before the last supply runs are added to the main trunk. This results in low airflow to each of the supply registers that these flexes or round ducts are connected to. Problem #19 An Animal Has Made A Nest with the Return or Supply Air Flex A collapsed flex may be found in an unsealed crawl space, such as under a mobile home. If the return flex has been ripped open by an animal, the flex will collapse in on itself when the system turns on. It is very important to make sure that the crawl space is sealed up. Problem #20 Duct Touching the Concrete Floor or Ground A duct making direct contact with a concrete floor or the ground in a crawlspace will eventually rot out and leak. I have seen this quite a bit where a downflow furnace has the supply duct under the home and the supply duct lowers down too far and is in direct contact with the wet ground. Other times, the concrete is continually wet and the duct rusts. The duct eventually rots out and the building owner calls the service tech out on a low airflow call. I hope this review was helpful with solving your airflow issues. Check out our video on this topic. If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Published: 04/14/2021 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 16 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel & https://www.facebook.com/acservicetech/

I put this list together to make sure that HVACR technicians don’t have to undergo the same frustrations, loss of time, and expenses that I did when trying to figure out solutions to vacuum problems! I am happy to say that I no longer have issues with my vacuums and if there is a problem, I can usually figure out the solution quickly without frustration! Below are my top 40 tips for techs when pulling a vacuum!
Hoses 1. Hoses may be rated for vacuum or just for positive pressure. Those rated only for positive pressure may not work well compared to vacuum rated hoses. Positive pressure rated hoses may leak some of the vacuum! 2. Replace your hose end gaskets because they break down and are torn over time! Gaskets are inexpensive and it doesn’t take a long time to replace them! These are obvious, potential leak spots if not taken care of! Also, adding a drop of refrigerant oil or Nylog on the gasket can help seal the gasket to the port of the unit. Gaskets: https://amzn.to/2D2pdqD Nylog: https://amzn.to/2MLJcch 3. Remember, the less hoses included in your vacuum setup, the less chances for vacuum leaks! 4. To attain a fast vacuum, use short, large diameter, vacuum rated hoses! 5. Vacuum hoses do not need to be expensive ones. I usually use two hoses total, one 3/8” hose for the vapor line port and one ¼” hose for the liquid line port. The 3/8” hose has a 3/8” hose end on one side and a ¼” hose end on the other side. The hose I use for the liquid line is 1’ long with ¼” connectors on the ends. 3/8” vacuum hose with a 1/4" connector and a 3/8" connector: http://amzn.to/2uYg6Ro ¼” vacuum hose 1’ long: https://amzn.to/2WNSBrN Sometimes on the liquid line, I use a 3/8" hose with 1/4" connectors on both ends: https://amzn.to/32NsWmS 6. Don’t trust hoses to hold the vacuum when performing a ten-minute standing vacuum test! Hoses and/or hose ends may leak! Depending on the setup used, you can avoid including the hoses during the "standing vacuum test". The standing vacuum test is also known as the decay test. It is when the vacuum pump is off and isolated while the vacuum gauge still reads the vacuum level in the system. To learn more about the step by step procedures, check out our Book ! Our full outline and sample pages are here ! 7. Don’t trust valves on hoses to be rated for deep vacuum. Often times, these valves will leak and the vacuum level will be lost. Only trust the vacuum rated valve on the valve core removal tools. 8. Set aside certain hoses specifically for doing vacuums only and not recovery or normal service. This way, you will always know that your vacuum hoses are in good condition.

9. If you use valve core removal tools in your vacuum setup, you will never get refrigerant oil into your dedicated vacuum hoses. This will keep your hoses in good condition for the next vacuum because you won’t have old oil that has absorbed moisture from the air, in your hoses. Example: After I break the vacuum with refrigerant, I re-install the valve core and remove the valve core removal tool from the port. Then I attach my normal service hoses for checking the charge. Because of this, my vacuum hoses are only used for vacuums and no refrigerant oil enters them. Video: https://youtu.be/PfdL3kZ3C6I 10. When using valve core removal tools, a valve core depressor is not needed on the end of the vacuum hoses. Make sure to remove the valve core depressor at the end of the vacuum hose because it will act like a restriction for your vacuum.
Valve Cores and Valve Core Removal Tools
11. Some people refer to these as “Schrader valves” instead of “valve cores” and vice versa. Some may never even hear them referred to as the other name so keep this in mind when you are communicating with techs! 25 pk of replacement valve cores: https://amzn.to/2L37UJU 12. If valve cores are left in the ports during the vacuum process, they will act like restrictions and prolong the time it takes to attain a deep vacuum. 13. If valve cores are removed with valve core removal tools prior to performing the vacuum, don’t try to put the valve cores back in until after there is positive refrigerant pressure inside the tubing, otherwise you will lose part of your vacuum! 1/4" valve core removal tool: http://amzn.to/2uYr8WL
14. If valve core removal tools are connected at the system ports during a vacuum setup, mount the vacuum gauge to the side of the valve core removal tool to get the most accurate vacuum level reading. 15. When vacuuming from two ports, attach the vacuum gauge to the valve core removal tool mounted to the larger of the two line-set tubes, the vapor tube. This will give you a more accurate vacuum than on the smaller liquid line. If the vacuum gauge were attached to the valve core removal tool on the liquid line, the vacuum level may read lower than what the rest of the system is currently at. 16. When vacuuming from two ports, include a 3rd valve core removal tool in the setup. This one will be mounted to the side of the valve core removal tool on the vapor line and the vacuum gauge can be mounted to this third tool. This third tool is used exclusively to valve off the vacuum gauge prior to adding positive refrigerant pressure in the lines. Remember that if the service valves are opened to break a vacuum, both refrigerant and oil will travel up into the vacuum gauge sensor. This oil may contaminate the sensor. (Also, make sure to remove the valve core from the side of the valve core removal tool, which is mounted to the large vapor line. This is where the third tool is mounted so you don’t want this section closed off by the valve core.) 17. After vacuuming, don’t remove the vacuum gauge prior to adding refrigerant into the system’s tubing to break the vacuum, otherwise air could enter the tubing during the removal. If a third valve core removal tool is used, simply turn the valve to the off position to protect the vacuum gauge.
18. When reinstalling your valve cores, make sure that the front of your valve core removal tool is not squishing the inner rubber gasket, or it will partially close off the section that the valve core needs to be inserted through. 19. After re-installing the valve cores, leak checking can be done very easily by using a cap with a small hole drilled in the end and bubble leak detector applied to the cap end. Using the cap with a hole in the end will not allow any bubble leak detector to enter the port and valve core area. If there is leak at the valve core, the technician will see a bubble being blown very quickly. Add the correct cap to the port when leak testing is complete. Small bottle of bubble leak detector: http://amzn.to/2ckWACn Spray bottle of bubble leak detector: https://amzn.to/3fWOlxK Related video: https://youtu.be/xyBM4PLQXK0 20. On a Mini-split, where only one port is available, two valve core removal tools can be mounted at this one port location. One valve core removal tool is used to remove the valve core from the port and the other tool can be used to valve off the vacuum gauge prior to breaking the vacuum inside the tubing with refrigerant. One vacuum hose can be used to connect from the tool to the vacuum pump 1/4" valve core removal tool: http://amzn.to/2uYr8WL 5/16" valve core removal tool: https://amzn.to/2WLddRz Video: https://youtu.be/k9uohbYDuRs
Manifolds 21. Some techs include their manifold gauge set in the vacuum setup. They may work well for a while but over time, they tend to leak. I had several gauge sets leak the vacuum and they caused me frustration and time trying to figure out what the problem was! The manifold gauge set may work fine for positive pressure but they may not work well for vacuums! 22. Adding a manifold to your vacuum setup will increase the amount of hoses needed to pull a vacuum. The more hoses, the more chances for leaks in your setup. 23. On a two port system, you can vacuum from both ports using a two hose setup without attaching the manifold gauge set. The removal of the manifold gauge set from the vacuum setup will reduce the potential for leaks and speed up the vacuum process because there are less restrictions, turns, and hoses. Related video: https://youtu.be/J4QvgpYFS9U Vacuum Pumps 24. Use a vacuum pump that has two or three ports to attach the vacuum hoses to instead of using a manifold as a tee. 25. Not all vacuum pumps are created equal. Some cheap version may not be able to pull a deep vacuum.
26. If the vacuum pump oil is not changed regularly, the vacuum pump may not be capable of pulling a deep vacuum. Don’t wait until the vacuum oil changes color. Replace the oil after use, especially after vacuuming an older existing system! Moisture from the system gets trapped in the oil and it doesn’t allow the vacuum pump to perform optimally. 27. Not all vacuum pumps come with a gas ballast. A gas ballast on a vacuum pump can help to reduce the amount of water that gets entrained in the vacuum pump oil. The gas ballast can be open prior to starting the vacuum pump until roughly the 15,000 micron level. After this, close the ballast and let the pump continue to lower the vacuum level. 28. Never mount a vacuum gauge near the vacuum pump because the vacuum gauge will show a much lower vacuum level than is currently within the system’s tubing.
Vacuum Gauge
29. Not all vacuum gauges are created equal and not all expensive vacuum gauges work well. Make sure to do your research before buying and check with other techs to see which brand/type seems to work well. Below is the one that I use in my company which is the same model that my students used in the shop at the HVACR school. Vacuum Gauge: https://amzn.to/2WM86AK 30. Keep the vacuum gauge as close to the unit as possible so that you can read the true vacuum level inside the system, not just the vacuum level in the hose near the vacuum pump. 31. During the vacuum, if the indoor blower motor is running, heat is introduced at the indoor evaporator coil. This reduces the possibility of water freezing in the tubing during the vacuum procedure. This is only needed when vacuuming a system with a high water content in the tubing.
Questions and Problems 32. Make sure to perform a pressure test prior to performing a vacuum. If there is a leak when you are trying to vacuum, you will pull the humid air from outside the tubing into the tubing. 33. The EPA 608 required vacuum level is currently 500 microns but most of us shoot for 200-300 microns for our finished vacuum level. 34. After reaching the required vacuum level, perform a 10-minute long standing vacuum test with the vacuum pump isolated from the system to verify that no water, air, nitrogen, or leaks exist in the system. After the 10 minute standing vacuum test, break the vacuum with refrigerant from the bottle or from the system. 35. A triple evacuation does not need to be performed if during the standing vacuum test of a single evacuation, the vacuum level does not rise. For instance, if you vacuum down to 200 microns and the vacuum level does not rise during the standing vacuum test with the vacuum pump off, the system is verified as having no air, nitrogen, water, or leaks. The triple evacuation is only needed if the technician is having a hard time removing the moisture from the empty system. Video of a single and triple evac on a minisplit: https://youtu.be/81EeY7SFYJc 36. If the unit you are vacuuming is used/old and the pressure test holds but the vacuum seems to leak, the leak spot may be at the top of the service valve where the stem O-ring seals up against the brass. This O-ring may be dry or was overheated during a brazing process. If the system is empty, try adding Nylog or refrigerant oil at the top of the valve on the inside and move the inner stem up and down to wet the O-ring! This may seal up the leak. Nylog: https://amzn.to/2MLJcch Video: https://youtu.be/Ks3MtPmXDUE 37. If you are vacuuming from both ports on a used system and the vacuum level is jumping around, there may be a problem with one or more oil globs blocking part of the tubing. Be sure to perform an oil blowout before trying to vacuum a used system that has oil throughout the inside of the tubing. The oil blowout procedure does not necessarily blow oil out of the system but will blow the oil onto the inner walls of the tubes to allow you to pull a vacuum through the tubes. Video: same as #36 https://youtu.be/Ks3MtPmXDUE 38. You can pull a vacuum with a one hose setup. With this setup, the vacuum gauge is mounted on the liquid line port and the vacuum is pulled from the vapor line port. However, this setup will take longer to pull a vacuum with than a two-hose setup because the metering device is found halfway down the tubing circuit which will restrict the flow of the vacuum. This is different than on a mini-split/ductless unit because with a mini-split, the metering device is in the outdoor unit, not half way down the refrigerant circuit. Video: https://youtu.be/J4QvgpYFS9U 39. If you are concerned about water freezing inside the tubing of an air conditioner, keep a few things in mind. Heat within the tubing will be removed by the vacuum pump but this heat will be replaced with the heat surrounding the outside of the line set tubing. Also, the indoor blower motor can be turned on which will introduce heat from the air at the indoor evaporator coil. This reduces the possibility of water freezing during the vacuum procedure. This is only needed when vacuuming a system with a high water content in the tubing anyway. In most circumstances, when vacuuming AC and heat pump systems, the freezing of water is not something that will occur due to the amount of exposed copper tubing that can allow for an easy absorption of heat. You can prove that there is not a frozen water problem during the standing vacuum test if after 10 minutes with the vacuum pump off, the vacuum level does not rise.
40. With a 10 minute standing vacuum test, you can prove that no leaks, water, air, or nitrogen exist within the tubing and that the system is ready for refrigerant! To learn more about step by step procedures, check out our Book or E-book and test your knowledge with our 1,000 question workbook along with the answer key ! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out our free quizzes to test your knowledge here !
If you want to learn the full Total Superheat Charging Method, check out this article ! If you want to learn the full Subcooling Charging Method, check out this article ! If you want to learn about Delta T, check out this article !
Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here ! Published: 7/22/2020 Author: Craig Migliaccio

About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 15 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel & https://www.facebook.com/acservicetech/

On a natural gas or propane furnace, there are typically 6 main reasons why a blower fan motor may not shut off and just continues to run. Before turning the power off to the furnace or opening the doors to the furnace, check the LED status code light (if equipped) for any error codes. On the furnace, there should be a correlating error code list. This will help in the initial diagnosis of the problem. Reason #1: One of the 24v Electrical Safety Switches Inside the Furnace Has Tripped A furnace may have the following safety switches. If any of these are electrically open, the blower motor may turn on and stay on until the switch automatically resets or is manually reset. · A draft temperature switch may be installed in a furnace to ensure that there isn’t a clog in the exhaust pipe. This should automatically reset when the temp lowers. · A thermal limit switch ensures that the heat exchanger area does not overheat. When the temp increases too high, this opens. This switch should automatically reset and close. · A flame rollout switch ensures that the flames don’t pop back in the combustion chamber due to a crack in the heat exchanger. This switch stays open and must be manually reset to close it. Before resetting, check for a crack in the heat exchanger along with the presence of CO. This is very important and a major safety concern. If a crack is present, the heat exchanger must be replaced for safety. · With a propane gas furnace, a low pressure (lp) gas switch may also be installed. This opens up the electrical circuit if the propane tank is low on propane, or if the gas valve supplying the furnace is turned off. Safety switches can be measured with a multimeter (like this one used) with one probe on the ground frame or common terminal of the 24v transformer and the other probe on a spade terminal of the switch. The meter should display 24v. Next move the probe on the switch spade terminal to the other side of the switch on the other spade terminal. 24v should be displayed. Repeat this step for each safety switch until you find the switch that is electrically open and 24v is not present. Determine why the switch has tripped such as overheating and fix the problem. If the switch is the problem, replace the switch with one of the same rating. Reason #2: A Bad Thermostat If the thermostat is not calling for heat, air conditioning, or fan to turn on, yet the fan is running, a quick test can be performed to see if the thermostat is the problem. Simply remove the face of the thermostat. If the blower motor stops, this indicates that the problem is in the face of the thermostat. Reason #3: Bad Thermostat Wiring · This may be due to a thermostat wire being flattened by a staple, or having been chewed by an animal (e.g. mouse, squirrel, etc.), which leads to the R and G wires accidentally connecting. · Use a multi-meter to check whether there is any power from G to common on the furnace control board while the door switch is temporarily held closed. · If there is power from G to common, turn the power off to the furnace and remove the thermostat face from the thermostat back plate. · Check the electrical resistance between R and G. There should NOT be any electrical resistance. If there is resistance between R and G, that means that the wires are accidentally connected and the thermostat wiring needs to be replaced. Reason #4: The Control Board Has Closed Contacts that are Welded Together · Turn on the power to the furnace · If there is no power measured on the G, Y, and W terminals, but there is 120 volts on relay contact going to the blower fan motor either on the heat or on cooling terminal, this indicates that the contacts inside the relay are welded together. This may have occured due to high current crossing the contacts which has melted the contacts together, resulting in a normally open switch being closed. Reason #5: Fan Limit Control Incorrectly Set or the Bimetal is Worn Out · Some older model furnaces have a fan limit control rather than a control board. The fan limit control determines when the blower motor turns on or off in heating mode, and acts as a limit switch to turn off the electrical gas valve in the case of overfiring and excessive heat. · The fan limit control may have a button which when pushed in manually turns on the blower motor. When the button is pulled out, the control is in auto mode. Make sure that the button is on auto, otherwise the fan will continue to run. · When the cover of the fan limit control is removed, a dial with three temperature settings is revealed. · If the bimetal on this unit senses the temperature is greater than the highest temperature setting, the blower motor will continue to run but the gas will be shut off. · The middle temperature setting is the temperature in which the blower motor is supposed to turn on. · The lower temperature setting is the temperature in which the blower motor is supposed to turn off. The problem could be that the bimetal is worn out due to expansion and contraction, and/or the lowest of the three temperature settings is too low. The setting should be 90-95 degrees F. If this setting is set at 90 or 95 degrees F and the blower fan continues to run, turn the dial a little to see if it temperarily shuts off. If it does, the fan limit control bimetal is worn out and the fan limit control should be replaced. Reason #6: Bad ECM Motor Module or Control Board Furnaces may be equipped with an ECM motor instead of a PSC motor equipped with a capacitor. Some common ECM motors are the Genteq 2.3 and 3.0 versions which are true variable speed motors. Other motor versions exist that are ECM constant torque (otherwise known as ECM multispeed motors) such as the X-13 and Broad Ocean models. If there is no power measured on the G, Y, and W terminals, but the ECM blower motor continues to run, the blower motor module may be at fault. Testing must be performed to determine if the motor and/or module are bad. For variable speed motors, use the TECMate Pro or Supco Tester to test the motor module to determine whether it needs to be replaced. If it is an ECM constant torque or multispeed motor, use the testing method in this video- https://youtu.be/AHAbkElOceY Still looking for an answer why the furnace blower fan motor wont shut off? Check out our video! " Furnace BLOWER FAN Motor WON'T SHUT OFF! 6 Reasons Why the FAN KEEPS RUNNING! "
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If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store

Tools that we use: www.amazon.com/shop/acservicetech

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Published: 5/3/2022 Author: Craig Migliaccio
About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 17 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel

An attic fan is used to lower the temperature within the building shell between the roof structure and the living space. The fan's job is to pull outdoor air into the attic from either the side gable vents or from the lower holes in the soffit. The fan then pushes the air out the attic through its penetration hole in the roof. The object is that fresh air (at the same temp as the outside air) is moving through the attic. Otherwise, non-circulating air would remain trapped within the attic space and continue to heat up during the summer day. Unless there is natural or mechanical ventilation (air movement), the sun warms the roof shingles and subsequently heat is stored within the attic. An attic fan is considered mechanical ventilation. Designing a roof with either natural or mechanical ventilation helps reduce the heat load on the building, which means the air conditioning system does not have to work as hard. The cost of running an attic fan is so much less than the cost of running an air conditioning system. (An AC unit may use 20 times more electricity to run compared to an attic fan.) The AC unit may not have to run as long to lower the temperature within the building because of the work done by the attic fan. You can avoid having to ventilate the attic if the structure is designed properly with a high level of insulation (such as spray foam sealing). This requires the right design for the building's location, and includes a very high upfront cost. However, the initial install cost may pay itself off in the end. I also want to point out, in this attic, where these photos were taken, the design of the attic ventilation is wrong. You can see that there is both an attic fan and a ridge vent. The ridge vent is the cut out section at the ridge of the roof line. You would have either an attic fan or a ridge vent, not both. If you have both, the attic fan will pull air from the path of least resistance which is through the closest spot in the ridge vent instead of from the lower soffet or from the side mounted gable vents. If you have a ridge vent only, the air will naturally rise from the lower soffets to the ridge vent, to exit the attic. Let's get into our ATTIC FAN problems!!! To adjust the attic fan thermostat, leave the cover on the thermostat and use a screwdriver ( see photo below ) to set the thermostat to the desired temperature setting (usually 90°F). The fan will turn on when the temp rises above 90°F and turn off when the temperature falls below 90°F. If the temp is set too low, the fan may never shut off, resulting in a high electrical bill, as well as little to no real heat removal from the building structure. If the temp is set too high, the fan will not perform as needed and will only run for short periods of time during the hottest days. You can test to determine whether the attic fan will turn on at the desired temperature setting, by temporarily setting the attic fan to a lower temperature. At this lower setting, the fan should run during a cooler day. Make sure to reset the fan back to 90°F after completing the test. Check to determine if there is power to the thermostat by placing a non-contact voltage sensor near the wire ( see photo below ). Do this with the power switch to the thermostat in the “On” position and then in the “Off” position. If the attic fan is not turning on, the power may be turned off at the switch or breaker panel. If there is power, but the fan is not running, remove the thermostat cover and use a volt meter to measure for voltage (see photo below) . Turn the temp dial, as necessary, during testing. Next, turn the power off to the attic fan. Once it is determined that there isn’t any power at the thermostat, try to push the attic fan blade (see photo below) to determine if the sealed bearings inside the fan motor unit have seized. If the blade does not spin freely , the attic fan motor or whole assembly must be replaced. If the blade spins freely when pushed, continue the diagnosis, by returning to the thermostat box. With the thermostat cover removed, check the thermostat switch by turning on the power. Insert one probe from a multimeter into the common and the other probe into a hot after the switch, before the motor ( see photo below ). Check for 120v power on the multimeter display with the thermostat set at 90°F. Then turn the temperature-setting knob down below 90°F and recheck for power. If power is verified coming into the thermostat but not past the thermostat, the thermostat switch is bad. If the thermostat allows power through but only at a lower temperature, verify the temp in the attic to see if the thermostat is still calibrated correctly. Use a bead temp sensor to measure temperature in the attic (see photo below) to determine whether the thermostat turns on at the set temperature. In the photo below, the thermostat has been set to approximately 70°F. The bead temp sensor reads the attic temp as 80°F. In this case, the thermostat should have closed the electrical circuit and allowed power to the fan motor. If not, the thermostat is bad. Sometimes the attic fan has a manual push test (see image below) that bypasses the temperature switch so that you can easily check to see if it will run. If power is sent to the fan motor and the motor will not spin, another test can be performed to check the fan motor itself. Before starting this next test, turn the power off and make sure the fan motor can spin freely. Stop the fan motor from spinning before measuring the motor's electrical windings. We can test the electrical windings to determine if they are intact or have opened. This can be done by testing the electrical resistance on the hot and common wires leading to the fan. Set the multimeter to the "electrical resistance" function. (Electrical resistance is the presence of a complete electrical path for current flow. This is measured with the power off to the unit.) An electrical resistance test is a quick check to see if a circuit is open or closed. It will also show how much resistance the circuit has.) Attach one clamp on the hot wire and the other clamp on the common wire leading directly to the motor (see photo below). The image below shows a reading of OL (Open Line) on the multi-meter. This reading means the electrical windings in the attic fan motor have melted and opened up. That is because in this case, the motor bearings froze and power was applied to the fan motor until the fan motor windings overheated and broke. The motor windings are bad in this motor. ( NOTE : Sometimes, even though the motor free spins, the windings may be bad.) Most attic fans have a shaded pole motor rather than a PSC (permanent split capacitor) motor. This is because capacitors fail due to high heat. Some older versions of shaded pole motors also have an oil spout which allows oil to be added to the oil bearings of motor. Oil musrt be added prior to summer and again after summer to keep the oil bearings lubricated. Otherwise, the motor will seize. Fan motors with an oil bearing were typically found on gable vents so that the motor could be exactly horizontal for the oil to flow into the bearings correctly. Newer attic fans, especially those mounted in the roof typically have sealed bearings and no oiling mechanisms. Looking for more info on troubleshooting attic fans? Check out our " Attic Fan Issues, Troubleshooting, Common Problems! " video below! Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Follow us on Instagram for Quick Tips and Updates here! Published: 6/14/2022 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 15 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel

In this HVAC training article, we will be discussing how to adjust the fan speeds on an indoor ECM variable speed blower motor and an ECM constant torque/multi-speed blower motor. These blower motor versions can be found in furnaces, air handlers, and packaged units. This is a follow-up to our other article on " Adjusting the Furnace/AC Airflow Speed on a 120v PSC Blower Motor ". If you have not read that yet, I would encourage you to do so! To start, ECM stands for Electronically Commutated Motor which means that the motor is capable of electronically controlling it's own speed, and therefore CFM, according to the desired output. However, they are limited based on the total external static pressure (TESP) in the duct. ECM blower motors do not require an external capacitor to operate. Additionally, they can be identified by the presence of a removable module/bell on the end of the motor. The constant torque/multispeed motor will have the smallest module. Remember that CFM stands for Cubic Feet Per Minute. Roughly 400 CFM is needed for every 1 ton (12,000 BTU/HR) of Heat Removal Capacity in Air Conditioning Systems. Example: 1200 CFM is needed for a 3 ton 36,000 BTU/HR system. In humid climates, 350 CFM per ton can be selected in order to remove more moisture from the air. The BTU/HR capacity or tonnage of the air conditioning system should be included within the model number of the outdoor unit. This BTU/HR capacity should be used to set the CFM for the indoor blower motor. The blower speed for a gas heater is selected so that it is comfortable for the building occupant but also so that the Delta T (Temp Rise) does not continue to rise. If the Delta T continues to rise, this is due to low indoor airflow. Usually, gas furnaces have a temp rise of 50°F. Oil Furnaces may have a temp rise of 50-60°F. Remember that a heat pump in heating mode will need to run with roughly the same airflow speed as during AC mode even though it may not be comfortable for the building occupant. This is done so that the maximum amount of heat is gained in the building from the refrigerant. ECM Multi-Speed Blower Motor (Broad Ocean Type) For an ECM blower motor with wires exiting the module (shown above), the speed is changed at the control board by moving the colored wire terminals. Only 3 of the 5 colored wires may be used at a time. These three are connected to the "Cool", "Heat", and "Fan" terminals on the control board. The wires that are used will determine the speed settings that the motor will run at. Note: (High voltage is always going to your blower motor along with the common for the 24 volts. The remaining colored wires are the speed selectors for this blower motor.) On this motor module, the speed wires are red, orange, blue, yellow, and black. You will need to look at what the programmed speed designations are for M1/M2/M3/M4/M5 on the wiring diagram of the HVAC unit. It is important to know that you can’t go by a normal color code to determine the speeds. You need to follow the wiring diagram inside the HVAC unit. These blower motor speeds are programmed at the manufacturer's factory for the specific equipment model number unit it is installed in. The factory may only set two or three of these colors as actual speeds. The remaining colored wires will be default speeds. ECM Multi-Speed Blower Motor (Genteq X-13) The line voltage and 24v common are connected at the top and are labeled as C, L, G, N. The 24v common is C and the ground wire is G. For a 120v unit, the L is the 120v hot and the N is the 120v neutral. For 240v units, both the L and N are hots. These are not switched off but are live all the time. This X-13 model shown above designates the speeds taps as numbers, not as colors, to denote each speed. On the motor, only one of the 5 numbered taps has 24v power at a time based on the speed desired at the control board. When one of the taps is powered with 24v, the motor will turn on and run at the selected speed. In order to determine or change the speed, check the wiring diagram of the furnace/air handler/package unit that the motor is installed in. This will show what speed each numbered tap is programmed as. For example, on a package unit, only taps 3, 4 and 5 may be programmed. In other units, it may be 2, 3, and 4 that are programmed. After understanding what speed each tap is programmed for, we can make proper airflow adjustments. In the pictured example above, if the #5 speed tap is programmed for 1600 CFM and #4 is programmed for 1200 CFM and #5 is presently connected to the "Cool" terminal on the control board via the black wire, we know that the unit is running at around 1600 CFM as long as the TESP across the unit is not too high. If 1600 CFM is too high of an airflow volume and only 1200 CFM is needed because the system is a 36,000 BTU/HR air conditioner, we can swap the yellow with the black wire on the motor module. This will cause the "Cool" terminal on the control board to be connected to to the #4 terminal on the motor module via the black wire. This means that any time cooling is called for by the control board, 24v will be present on the #4 terminal of the motor module to turn the motor on and to run at roughly 1200 CFM. If the terminals are present at the motor module (ECM X-13) you can switch speeds at the blower motor location. If you have a plug instead (ECM Broad Ocean) you can only make the adjustment at the control board or at the plug terminals at the end of the wiring. Make sure power is off when doing any adjustment. You can verify the actual CFM by measuring the TESP of the system and comparing it to the manufacturer's airflow data sheet. Variable Speed Blower Motor ( Genteq 2.3, 16 pin connector) In the example above, an ECM 2.3 16 pin variable speed motor is connected to an air handler control board. Wires from the 16 pin plug are connected to this board. On this control board, there are multiple adjustments for the airflow speeds. These adjustments can be made by pulling the single wire connector and moving it to another single tab positioned horizontally in each row. The airflow adjustments on this board are pictured below. The following list refers to each adjustment starting from the bottom and moving upward. - The "Continuous Fan" refers to when the G terminal is powered for the fan only to run. -The "Blower-on and Blower-off delay" time period can be selected. -The "AC/HP CFM Adjust" is the airflow volume to be set for system, efficiency, comfort. -The "System Type" is the CFM per ton to be adjusted between low, normal and high. -The BTU/HR size is selectable between 48,000 42,000 36,000 or 30,000 BTU/HR -The "AUX Heat" makes sure that there is enough airflow when elect strip heat is called. Variable Speed Blower Motor (Genteq ECM 3.0, 4 pin connector) In the example of an ECM 3.0 with a 4 pin connector, the wires are not switched or moved to adjust the airflow settings. The control board is communicating with the blower module in order to determine the airflow volume needed. This control board is out of a variable speed furnace with a modulating gas valve that has a variable speed inducer motor. In this case, to adjust the blower speeds, move the dip switches (in the red section of the control board) to the positions shown in the manufacturer's installation instructions. The installation instructions for this furnace are needed in order to be able to know how to set these dip switches. If the instructions are not with the furnace, you can look up the model number of the unit and search for the installation manual via a google search. On this board, pins 3, 4, and 5 on the SW1/1 through SW1/8 dip switch block have to do with air flow. The continuous fan is marked SW3. The SW2 indicates the air conditioning size. Upon initial installation, these dip switches need to be adjusted for the particular unit, size, and application. To adjust the dip switches, turn the power off and take a flat head screw driver to lightly push the dip switches to the on/off desired position for each numbered switch. Match the positions to the desired pictures within the manufacturer's installation literature. In order to measure air flow you could use a flow capture hood, a rotating vane anemometer, or a hot wire anemometer . You could also use the Temp Rise Formula which you can learn about in our " HVAC Temp Rise Formula used to Measure Airflow CFM " video. I hope this helps you understand how to adjust the airflow speed on ECM Blower Motors! Be sure to check out our previous article on " Adjusting the Furnace/AC Airflow Speed on a 120v PSC Blower Motor " if you haven't read it yet! Also, if you are looking for a video to better help understand this topic, check out our " Adjusting HVAC Blower Speed CFM on Furnace & AC Units! " video below! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Published: 05/19/2021 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 16 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel & https://www.facebook.com/acservicetech/

In this HVAC training article, we will be discussing how to adjust the fan speeds on an indoor PSC blower motor in furnace and air conditioning units. PSC stands for Permanent Split Capacitor and these motors can be easily identified by their direct connection to a capacitor. Remember that CFM stands for Cubic Feet Per Minute. Roughly 400 CFM is needed for every 1 ton (12,000 BTU/HR) of heat removal capacity in air conditioning systems. 350 CFM per ton can be used in humid climates to remove moisture from the air. The BTU/HR capacity or tonnage of the air conditioning system should be included within the model number of the outdoor unit. The blower speed for a gas furnace is selected so that the airflow is comfortable for the building occupant but also so that the Delta T (Temp Rise) does not continue to rise. If the Delta T continues to rise, this is due to low indoor airflow. Usually, gas furnaces have a temp rise of 50 F. Oil Furnaces may have a temp rise of 50-60 F. Remember that a heat pump in heating mode will need to run with roughly the same airflow speed as during AC mode even though it may not be comfortable for the building occupant. This is done so that the maximum amount of heat is gained in the building from the refrigerant. 120v PSC Blower Motor in a Furnace Always turn off power at the furnace or air handler before changing blower motor speeds on the control board. 120v PSC blower motors may come with multiple power wires that are color coded. The white wire is usually the common and the other colors are for separate speeds. You may ask, how do I determine which wire is the highest speed and the lowest speed on a PSC blower motor? This is done by taking electrical resistance measurements using a multimeter. In this example, we will be using a 120v PSC motor from a furnace. First, turn the power off to the furnace. Take a pic of where the blower motor wires are mounted. The white will be mounted to the common/neutral bar. Remove the blower motor wires from the control board or other connections. Place the red multimeter probe on the white common wire of the blower motor. Use the black multimeter probe to touch each of the other color-coded wires, one at a time. The electrical resistance from common to each speed is measured. In this example: The red and white measures 5.3 ohms. The yellow and white measures 4.3 ohms. The blue and white measures 3.3 ohms. The black and white measures 2.6 ohms. The resistance value of each pair changes, depending on the second wire selected. The second wire is the one other than the common in the pair. The color wire with the lowest resistance value is the highest speed. The color wire with the highest resistance value is the lowest speed. In the example above: Red= Lowest speed Yellow= Second from Lowest Blue= Second Highest Black= Highest Now that we have determined the speed of each of the color wires on the motor, we will look at a 120 volt furnace control board. On the board in this example, the white wire is connected to the neutral/common location. The blue wire is connected on the heat terminal. The black wire is on the cooling terminal. The other wires are connected on M1 & M2. The M1 and M2 can be referred to as spare/park and these terminals do not connect to any circuit on the board. They are simply a place to park the unused speed wire terminal ends so that they do not accidentally short against a ground while the system is running. In this example, in cooling mode the unit is running at its highest fan speed selected. If the heat speed needed to be changed to a slower speed, we would simply turn the power off to the unit and switch the blue with the yellow wire. Then we would turn the system on and check the temp rise in heating mode mode to make sure that it does not continually increase. I hope this helps you understand how to adjust the airflow speed on a 120v PSC Blower Motor! Keep an eye out for our article on adjusting airflow speed on ECM Blower Motors! Also, if you are looking for a video to better help understand this topic, check out our " Adjusting HVAC Blower Speed CFM on Furnace & AC Units! " video below! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! Tools that we use: www.amazon.com/shop/acservicetech Follow us on Facebook for Quick Tips and Updates here! Published: 05/12/2021 Author: Craig Migliaccio About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 16 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel & https://www.facebook.com/acservicetech/

Use an additional valve core removal tool in your vacuum setup to valve off and protect the vacuum gauge sensor from oil contamination when refrigerant is added into the tubing. If the sensor gets oil on it, the sensor will not perform correctly and the sensor will need to be cleaned. Often this is accomplished with rubbing alcohol but always follow manufacturers' instructions for cleaning. CPS Vacuum Micron Gauge - http://amzn.to/2v1nM3O 1/4" Appion Valve Core Removal Tool - http://amzn.to/2uYr8WL 5/16" Appion Valve Core Removal Tool - https://amzn.to/2JHmfbP

The answer is no because the refrigerant rejects heat in the condenser so the pressure and temperature of the refrigerant should lower. The refrigerant starts off in the condenser as a superheated vapor and after it rejects heat, it changes from a vapor state to saturated. After it rejects enough heat, the refrigerant changes to a subcooled liquid. In this picture, we see a saturated temperature of 105°F and a line temp of 93°F. 105 - 93 = 12°F of Subcooling
It is possible for the refrigerant to stay saturated instead of subcooling if the system is extremely low on refrigerant. A system that is very low on refrigerant may read 0-3 degrees of subcooling. Typically, there will be at least a small amount of subcooling measured. If the refrigerant is rejecting heat at the condenser, there is no way for the pressure or temperature of the refrigerant to increase as it makes its way through the condenser. It will either exit the condenser as saturated (saturated is liquid and vapor refrigerant in the same location) in a low refrigerant scenario or the refrigerant will be subcooled (subcooling is the lowering in temperature of the liquid refrigerant). If you are measuring negative subcooling, make sure your measurement locations are correct, otherwise you may want to recalibrate your tools!
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I have been asked, “Can we braze mini-split systems instead of flaring them?”. The answer, technically, is yes. The only question is in a warranty situation, will the manufacturer accept an indoor unit with the flares cut off? In most cases, they should accept them and the manufacturer reps that I have spoken with have said that it is not a problem. However, technicians should verify this themselves with the manufacturer of the particular equipment that they install. Of course, when we braze copper line set, we make sure to flow nitrogen or another inert gas through the tubes so that oxidation does not occur inside the line set. The technician will still need to flare the connections to the outdoor unit since there are no stubs to braze, only service valves with flare connections. There is usually only one service port at the outdoor unit, and it is on the vapor service valve. This is where the nitrogen will be introduced. Make sure the small, liquid line is not connected to the flare connection on the liquid service valve. The nitrogen will exit out of this small, liquid line tube. Step by Step Process of Brazing Mini-Split Tubing : 1. The technician will begin by flaring the large suction line tube and connecting this to the outdoor unit. The small, line set tube should not be connected at this point but will remain open on the end. (The small line set tube would be referred to as the low pressure liquid tube since the active metering device is usually in the outdoor unit of a mini split system. This means that during cooling mode, the metering device will lower the pressure of the refrigerant before it enters the small line set tube.) 2. The flare connectors will need to be cut off of the indoor unit copper stubs and the copper tubes must be reamed in the downward position so that any small pieces of copper will fall out of the tube. 3. The copper stubs from the indoor unit should be swaged and the large and small line set tubes should be run into place and inserted into the swages. * Video on how to swage copper tube with every type of swaging tool * 4. Next, a flow regulator must be connected onto a nitrogen tank and set to flow at 2-3 CFH (cubic feet per hour). The nitrogen hose will then be connected to the outdoor unit vapor service port. The nitrogen will enter the vapor service port, flow through the large vapor line, through the evaporator coil, and out of the small line set tube near the small low pressure liquid service valve. The nitrogen will not pressurize the tubing but will push any oxygen out of the tubing during the brazing process. This will also help to dehydrate the lines prior to vacuuming. 5. The technician will then braze the swage joints using a small brazing tip and 15% silver brazing rod. The swage joints will either be behind the indoor head unit, inside the building (while the head unit is tilted upward to gain access to the underside of the unit) or outside the building if the stubs penetrate directly through the outside wall. Make sure to use a heat shield when brazing inside the building or outside near the siding. 6. The nitrogen will then be disconnected, and the small, low pressure liquid line will be flared and connected to the outdoor unit flare connection. Make sure to tighten all flare connections to the specified foot/lb torque value. Usually this is 12 ft/lb for ¼” OD copper tube and 27 ft/lb for 3/8” OD copper tube, but always follow manufacturers instructions to avoid future leaks or problems at the connections. 7. The system will then be ready for a pressure test to check for leaks. It’s okay to use flares as connections as long as you are sure they won’t leak. Below is a video on 10 reasons why flares may leak as well as ways to make sure that they won’t. Let me know your experience if you had to warranty an indoor mini-split head unit with cut off flares. I would love to know if anyone is having any trouble with a warranty based on the cut off flares and with which manufacturer. You can comment below or email me at info@acservicetech.com, thanks! Check out our book “Refrigerant Charging and Service Procedures for Air Conditioning”. The full outline is available at https://www.acservicetech.com/the-book
If you have already purchased our book, be sure to tell local HVACR Instructors about our book and what you think of it. We would love to get the book into the hands of the next generation of HVACR Technicians!
Published: 9/12/2019
Author: Craig Migliaccio About the Author:Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 15 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel