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Ductless Mini-Split Step-by-Step Installation

Updated: Jun 26, 2023


In this step-by-step installation, we will be covering the full installation of a ductless Mini-Split heat pump system. This system happens to be a Cooper&Hunter Dakota Series Hyper Heat model. This installation process will be very similar to other manufacturer’s Mini-split systems. However, it essential to read the install instructions and flare torque specs of the exact model you are installing. A variety of tools and techniques are needed to complete the installation of a ductless Mini-split system. As we progress through the installation steps, each tool and technique will be discussed.

Step 1: Locate the general area where the indoor and outdoor units need to be mounted. When possible, plan to install the indoor head unit on the inside of an exterior wall. Do this in a location where the line set tubing can exit through the wall and go directly down to the outdoor unit connection points.


The indoor unit location should be away from fluorescent lights, as they may interfere with the system’s remote-control operation. Make sure that the location of the indoor unit allows for easy access to the air filter which is located at the top of the indoor wall unit. Next, determine if the outdoor unit needs to be hung on a concrete wall with a bracket, mounted to an elevated deck, or placed on a pad near ground level.


System installed in this article: https://amzn.to/3aXbmyV

Mini-Split Wall Bracket: https://amzn.to/2YG1THv

Step 2: After the general install area for the indoor and outdoor units has been identified, start the installation process with the indoor unit. Locate the wall studs with a stud finder, or by knocking. Confirm the stud locations.

Mount the indoor unit wall plate to the studs using weight bearing fasteners with large heads. Lags with washers or screws with washers will work (see photo below).

Step 3: Determine the location of the hole that must be cut through the exterior wall. This hole is for the line set tubes, electrical wire, and condensate line to pass through to the outside of the building. This single hole is usually 2 3/8” or smaller in diameter. To determine where the hole needs to be located, use the carboard template from the manufacturer, or with measurements from the back side of the indoor unit (see photos above). Use a pencil to lightly draw the circle. Drill a screw into the sheetrock at the center of the circle to determine if a stud in the way. Next, drill two more screws on the outer horizontal edges of the circle to make sure that there isn't a stud in either spot. If there is a stud located where the hole needs to be, the metal wall plate for the indoor head unit needs to be shifted horizontally, so that the 2 3/8” hole will miss the stud.

Step 4: To probe through the wall, draw a small X on the wall where the center of the hole will be. Place a metal probe (actually an insulation hanger) into the drill chuck just like a drill bit. Drill through the X with the probe on a slight downward angle through the sheetrock, insulation, plywood and siding (see photo below).

Locate where the probe exits through the outside wall. Determine if this location is satisfactory for the line set to exit through.

Step 5: To drill the hole through the interior wall, determine the size hole-saw bit to place into the drill. If you would like to sleeve the hole with 2” schedule 40 PVC, use a 2 3/8” hole-saw bit. Drill through the sheetrock slowly on a slight downward angle.

Step 6: Before drilling the hole through the exterior siding and sheathing, switch the drill to counterclockwise (reverse). Using the drill bit in reverse reduces the risk of cracking the siding while drilling a hole through it. Use the pilot bit of the hole-saw to penetrate the siding first. Keep the drill at a steady angle while applying the least amount of force necessary, as you drill the 2 3/8” hole through the siding. The less the pressure/force being exerted on the drill, the less likely the outer bit will catch on the siding and tear a crack in it. Keeping the drill at a high RPM may also help the siding from being damaged. Make sure this hole is going on an angle slightly upward. Complete the hole by penetrating through the plywood sheathing. Push the interior wall insulation to the sides so that nothing is blocking the hole. This makes it easier to pass the wires and tubes through to the outside.

Step 7: If using a sleeve, push the sleeve material through, mark the ends with pencil, and pull the sleeve out. Cut the sleeve to size using a hand saw. In this instance, a 2” PVC sleeve is being used. Slide the finished sleeve into position and put a screw through the sleeve and into the plywood sheathing so that the sleeve does not move when pushing the line set tubes through it. Also, add sealant where the PVC meets the siding and where the sleeve meets the sheetrock (see photos below).

Step 8: Plan for the connection of the electrical wiring to the back of the indoor head unit. The normal wiring supplied with mini-split has an outside rubber casing that is UV protected and outdoor rated. There are four separate stranded wires inside the casing . Three wires are for the communication/power and one is the ground. Remember that the communication wires have high voltage power running through them, so make sure to follow local codes when installing the wiring from the indoor unit to the out d add a few extra feet to ensure there is a sufficient amount to cover the required distance. Fish the cable through the conduit and leave roughly 18” of extra cable past the conduit on both sides. If EZ-IN is used, the four wires are already inside the conduit.

Step 10: In order to be able to connect the conduit to the back of the indoor head unit, add a connector to the end of the conduit. First, slide the four wires through the hole in the indoor head unit, then affix the conduit connector in place. The wires will now be extending out of the front electrical compartment (see photo below).

Step 11: Mount each of the three communication wires to the terminals in the front of the indoor head unit. Tighten each in place. Note what color wire is mounted on each terminal designated as A, B, C or 1, 2, 3. These same color wires will be mounted to the matching A, B, C or 1, 2, 3 terminals at the outdoor unit (see photos below). The green wire must be connected to the ground frame of the indoor unit and the outdoor unit.

Step 12: Carefully bend the copper line set tubes on the back of the mini-split 90 degrees so they face toward the wall and are lined up to go through the hole in the wall. Also, bend the tubing on a slight downward angle (see photos below).

Step 13: Tape the condensate line and electrical cable/conduit together with the line set tubes. When doing this, make sure that the condensate line is positioned at the bottom so that the water travels properly when installed (see photo below). To secure these together, electrical tape is good to use because with each wrap, you can squish the lines together to reduce the outside dimension of the objects within the tape. This makes it easier to fish the objects through the hole in the wall.

Step 14: Fish the objects through the hole/sleeve in the wall and hook the indoor wall unit onto the metal mounting plate. Make sure that the indoor wall unit is hooked at the top and snapped into position at the bottom.

Step 15: Mount the remote to the inside wall, if desired. The indoor work is now complete.


Step 16: Move outside and carefully cut the tape off the electrical wiring, condensate line, and the line set tubes.


Step 17: Bend the line set tubes by hand one at a time. In order to do this, support the bottom of the tube by placing a hold back finger or two inside the hole in the wall (see photo below). With the other hand pull down on the tube. Move the hold back fingers in different spots as you are bending the tube downward. Doing this creates many bend spots which helps prevent the tube from developing a kink.

Step 18: Prepare the copper tube line set that will connect from the stubs of the indoor head unit to the outdoor unit. To prepare the tubing, uncoil each tube by holding the end of the tube down with your foot and rolling out the coil on a concrete walkway or on the ground. This will produce a straight section of tube. Determine the length of tube needed by measuring the distance from the stubs of the indoor unit to the outdoor unit connectors. After determining the distance, add a few feet and cut each tube to length. Use a utility knife to cut the outer insulation. Use a tubing cutter to cut the tube (see photo below).

Step 19: Hold the end of the tube in a downward position and use a deburring tool to deburr the end of the tube. Add a flare nut at the end of the tube and slide the nut further up the tube. Put the copper tube into a flaring tool block and lock the nut in place.


Step 20: To produce a high-quality flare, use an Eccentric Flaring tool https://amzn.to/2OBxGlMl or https://amzn.to/367jBXj. Make sure that the tube is roughly 1/8” out of the flare block. If the flaring tool has a tubing stop built into it, push the tube into the mechanism until the tube cannot move inward any further. Lock the tube in place (REMEMBER TO HAVE THE FLARE NUT ON THE TUBING!!!). Make sure that there is a dab of refrigerant oil, or Nylog https://amzn.to/2MLJcch on the eccentric cone. Rotate the cone clockwise toward the copper tube until the eccentric tool clutch opens up. This means that the flare is complete. Back the cone up counterclockwise out of the way and then release the copper tube from the block. Push the nut forward over the flare. Do this for both line set tubes.


Step 21: Add a small amount of Nylog or a dab of the refrigerant oil that is in the system, to the flare face. When using Nylog, only a very small amount must be used. It is only to be used on the flare face and on the flare adapter, so that it does not enter the inside of the tube. Push the flare face and flare adapter together and rotate the nut until it stops moving.

Step 22: Locate the ft/lb torque specifications for the tubing size in the manufacturer’s manual. In this case, the ft/lb torque of this model unit is 11.8 ft/lbs for ¼” tubing and 19 ft/lbs for 3/8” tubing. Hold the flare adapter in place with an adjustable wrench, and place a torque wrench https://amzn.to/2NRR68Q on the flare nut. Tighten to the specified torque value (see photo below). Do this for both line set tubes at the specified torque value for each.

Step 23: Bend the remaining line set tubing into place and cut the ends to length so that they meet the connectors on the outdoor unit.


Step 24: Deburr the ends of the tubes with each tube in the downward position (see photo below) so that any copper shards fall out of the tube instead of into the tube.

Step 25: To produce a high-quality flare, use an Eccentric Flaring tool. Make sure that the tube is roughly 1/8” out of the flare block. If the flaring tool has a tubing stop built into it, push the tube into the mechanism until the tube cannot move inward anymore. Lock the tube in place (REMEMBER TO HAVE THE FLARE NUT ON THE TUBING!!!). Make sure that there is a dab of refrigerant oil, or Nylog on the eccentric cone. Rotate the cone clockwise toward the copper tube until the eccentric tool clutch opens up. This means that the flare is complete. Back the cone up counterclockwise out of the way and then release the copper tube from the block. Push the nut forward over the flare.

Step 26: Add a small amount of Nylog https://amzn.to/2MLJcch, or a dab the matching refrigerant oil that the system has to the flare face. When using Nylog, only use a very small amount. It is only to be used on the flare face and on the flare adapter, so that it does not enter the inside of the tube.

Step 27: Push the flare face and flare adapter together and rotate the nut until it stops moving. Use the same ft/lb torque specifications for each tube size as found in the manufacturer’s manual (see Step 22). Hold the flare adapter in place with an adjustable wrench and place a torque wrench on the flare nut (see photo below). Tighten to the specified torque value. Do this for both line set tubes at the specified torque value for each.

Step 28: Pressure test the system to see if there are any leaks. (Be sure to check the flare joints.) This can be done at a nitrogen pressure of 300 psi on newer systems for at least ten minutes, but preferably for an hour. On older systems, test at a lower pressure so that you do not create a leak by adding excessive pressure. Using a digital manifold set allows even very small incremental changes to be seen during the pressure test. Also, if there is a drop in pressure, the digital manifold set helps for a leak to be identified quickly. Always make sure to follow manufacturers’ specifications for the exact amount of nitrogen pressure to test the system to, as those specifications supersede these instructions.

Step 29: To pressure test, use a 60 cu ft nitrogen tank with a regulator http://amzn.to/2bXdR5f and a manifold gauge set http://amzn.to/2aenwTq along with hoses http://amzn.to/2aBumVI. The first gauge on the nitrogen regulator shows the pressure in the tank. The second gauge shows the pressure exiting the regulator. Before opening the tank, make sure that the thumb screw to the regulator is turned counterclockwise outward. The ¼” port on the regulator connects to a manifold gauge set via the yellow service hose attached to the middle of the manifold gauge set. Connect the blue hose from the gauge set to the port on the vapor line of the outdoor unit. To do this, use a 5/16” to ¼” adapter https://amzn.to/34HSran to reduce the port size of the outdoor unit to the hose size. Keep the manifold gauge set handles shut, and open the nitrogen tank handle. Next turn the thumb screw on the nitrogen regulator clockwise to the desired pressure. Next, bleed the air out of the hoses at the gauge set and then reconnect to the system. Open the blue handle on the gauge set to allow the nitrogen into the system. Shut the handle upon reaching the desired pressure. After the handle is shut, tap on the gauge and note the pressure measurement. Also, make sure to shut the handle on top of the nitrogen tank and detach the yellow hose from the regulator. For safety purposes, release the nitrogen from the regulator and back out the thumb screw on the regulator counterclockwise.

Step 30: Perform a ten minute or longer (preferably an hour) pressure test to see if the pressure falls. During this test, while there is high pressure in the system, add “Big Blu” bubble leak detector onto the joints. "Big Blu" is an anti-corrosive liquid leak detector solution that makes a bubble or foaming action at a leak location. Do not use dish detergent and water as the chemicals in dish detergent can eat away at fittings over time.

Step 31: If there aren't any leaks found, as indicated by no drop in pressure, wipe off the excess leak detector from the joints and slowly release the nitrogen pressure from the manifold. Once the tubing pressure reaches 0 PSIG, detach the manifold gauge in preparation for vacuuming the tubing system.


Step 32: If you have not done so already, prior to setting up for a vacuum, use a valve core removal tool to remove the valve core (Schrader valve) from the 5/16” port of the system. Also remove the valve core from the top side of the 5/16” valve core removal tool. Leave the body of this valve core removal tool in place on the 5/16” port. Add another ¼” valve core removal tool to the top part of the first tool. Add a vacuum gauge at this location (see photos below).

Step 33: To connect the vacuum hose setup to the system, run one vacuum hose from the vacuum pump to the end of the 5/16” valve core removal tool. The valve on the 5/16” valve core removal tool is used to trap the vacuum. The valve on the ¼” tool above the 5/16" valve core removal tool is used to isolate the vacuum gauge. At this point, keep both valves in the open position.

Tools used for the Vacuum:

  • Appion Red 3/8" to 1/4" Vacuum Hose - http://amzn.to/2uYg6Ro

  • CPS Vacuum Micron Gauge - http://amzn.to/2v1nM3O

  • CPS 4 CFM Vacuum Pump - https://amzn.to/2DxgPwY

  • 1/4" Appion Valve Core Removal Tool - http://amzn.to/2uYr8WL

  • 5/16" Appion Valve Core Removal Tool - https://amzn.to/2JHmfbP


Step 34: After the vacuum setup is attached, turn on the vacuum pump. Allow the vacuum gauge to reach roughly 1,000 microns before closing and then reopening both valves on the valve core removal tools. This is done to remove any air surrounding the valves.


Step 35: Allow the gauge to reach roughly 200 microns. Close the valves again, and then reopen them. The micron level may rise to roughly 250 microns after moving the valves. Allow the gauge to reach 200 microns again. However, this time, shut the valve on the 5/16” valve core removal tool. Shut the vacuum pump off. (Per EPA 608 guidelines, a vacuum of 500 microns must be attained prior to allowing refrigerant into the tubing.)


Step 36: Wait at least ten minutes with the vacuum pump isolated from the system, to see if the micron level rises. Remember that the vacuum gauge is connected to the system, and is reading the true vacuum level while the pump is off. This test is referred to as the “Ten Minute Standing Vacuum Test” or the “Decay Test”. If the vacuum level continually rises, there is a leak in the system. If the vacuum level rises and then plateaus, there may be water in the system.


Step 37: If the vacuum level stays below 500 microns and does not continue to rise, the vacuum is good. Either break the vacuum with refrigerant from the bottle, or by opening the service valves on the system. If the line set length does not exceed the maximum length posted by the manufacturer, you only need to open the service valves. This is because the refrigerant charge amount does not need to be increased. Prior to opening the service valves, close the valve core removal tool valve to isolate the vacuum gauge. This will protect the vacuum gauge sensor from refrigerant oil and positive pressure.

Step 38: Open the service valves on the system with the appropriately sized Allen wrench, or a ratcheting wrench. Replace the valve core at the 5/16” port using the existing 5/16” valve core removal tool mounted to the port. To ensure that air is not introduced to the refrigerant charge, purge the small amount of air inside the valve core removal tool before screwing in the valve core.

Before disconnecting the valve core removal tool, test for a leak at the back of the tool by applying “Big Blu” bubble leak detector https://amzn.to/3kZTuXC to the end of the tool to see if any bubbles form. If no bubbles form, remove the tool and place a cap on the port.

Step 39: Seal the hole hole the exterior wall and around the tubing, cable, and condensate line so that rain does not enter the wall of the building (see photo below). This can be done with exterior sealant such as Geocell tri-polymer sealant https://amzn.to/2G33ccN.

Step 40: Add a cover over the line set, cable, and condensate line. This can be Mini-Split Slim-Duct casing, or a plastic downspout. To install the downspout, cut the entire length of the back of the downspout (see photo below). Add a 60-degree elbow at the top, and cut that elbow on an angle so it looks like it is penetrating through the siding. In reality, it is just sitting flush against the siding. An alternative option is to run the downspout up to the bottom of the soffit.

Use several two-hole plastic or aluminum straps to secure the downspout over the tubes on the wall (see photo below) . Use stainless steel screws to secure the straps. These screws do not rust and therefore will not stain the siding.

Step 41: Run the electrical cabling down along with the line set tubes and lightly zip tie them together. Run the electrical cabling into the outdoor unit’s electrical panel and mount it in place with the appropriate connector.


Step 42: To connect the four cables to the outdoor unit, cut them each to length, strip them, and add crimp connectors to the end of each stranded wire. Place each connector under the appropriate mounting screw to line up the color wire with the designated terminals A, B, C or 1, 2, 3 like at the indoor head unit terminals (see photo below). Tighten each connector in place, including the ground.

Step 43: To connect the 240-volt power wires, dry fit flexible conduit in place from the bottom of the disconnect box to the outdoor unit and cut it to length. Fish the three THWN coated stranded wires through the flexible conduit with an extra foot of length on each side of the conduit. Cut the wires. Add the connectors to the ends of the flexible conduit. Mount the conduit to both the outdoor disconnect and to the outdoor Mini-Split unit so that the wires are in each location. Connect the power wires and ground wire to the lugs inside the disconnect (see photos below). Connect the power wires and ground to the outdoor Mini-Split unit. Put the electrical covers on both the electrical disconnect and the outdoor Mini-Split unit.

Step 44: You are ready to turn the power on. Remove the disconnect plug at the outdoor disconnect box, and turn the indoor building breaker to the on position. Use a multimeter to test for the correct power at the outdoor disconnect. When ready, insert the disconnect to turn the system on (see photo below).

Set the indoor thermostat to the desired mode and enjoy the comfort of the system!

If you are an HVACR tech and this is not your home, hurry up, clean up, and get to your next job! People always say it must be nice to work on air conditioning systems in the summer. I reply with, "Not really, because as soon as you get the AC on, you need to leave and go to the next job where the AC is broken!"


Remember, you must be EPA 608 Certified before buying or handling refrigerants per EPA 608 law. If you want to learn more about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book at https://www.acservicetech.com/ac-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 our other article on checking the refrigerant charge of a Mini-Split unit! https://www.acservicetech.com/post/checking-the-charge-of-a-mini-split-unit





Published: 11/25/2020 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/

2 comments

2 Comments


Is there a minimum length for a mini-split line set?

If yes, what is the purpose of setting a minimum length?

If the line set is shorter than recommended minimum length, will that damage the unit in some way, or adversely affect performance?


Does the reason for stipulating a minimum line set length have to do with making sure the pre-charge amount provided by the manufacturer does not create an overcharge . . . in other words, with a shorter line there would be too much refrigerant? If that were the case, couldn't that be remedied by simply removing a calculated amount of refrigerant to compensate for the shorter length?


The installation manual for the unit says 15' minimum length.…

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In the illustration for step 38, the valve core removal tool on the vacuum gauge appears to be open. Should it not be closed to protect the gauge as you open the service port?

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