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I thought I would share a write up on a 4 ton Mr.Cool Universal install on an A/C upgrade to heat pump done using traditional methods, not their pre-charged line set.
This is only my 3rd install. I have my 608 license but not a plumbing or electrical license so some of this could lack the accuracy their experience could provide.
I ordered through Ingram's and had a great experience. It shipped out next day on an afternoon order and took 5 days to go across the country with great communication along the way. The delivery truck had a pallet jack and they placed it right where I needed it.
The old system was maintained every year by an HVAC company with no complaints from the owner (my parents) and no service calls during its 10 year life.
The key learnings:
The service valves are on the opposite side of most A/C units. I knew this going in and bought extra line set to extend the existing.
You may need to add flex line and a junction box so you can splice in more t-stat wire to lengthen the thermostat wire as it also needs to go to the right side just like the line sets. The power disconnect was installed on the right for the prior system so I had extra #6 wire to work with.
I put the unit on a pad as they live in a desert climate and it rarely drops below freezing. The Schroeder valves are on the bottom of the service valve. I had to dig a hole in the ground to give working room for the valve core removal tool to pull both for the vacuum.
The pads Ingram's sells are fine but I’d rather pay more for a heavy duty pad that is a bit taller. If I had another day, I would have poured a concrete pad and placed anchor bolts. If you do, keep in mind the front right foot is in front of the service panel so it can’t stick up much without getting in the way.
The service valves are 6mm and 8mm. A regular service wrench won’t work, but I needed it to uninstall the A/C.
Get a 1/2” and 1” 90 degree bend for the electrical knock outs for power and thermostat so they head straight back to the wall.
The old line set was somehow not perfectly round. I had to use a swaging tool to widen the narrower spots. This wouldn’t have been an issue with brazing as it can handle gaps and wasted a lot of time.
Since we were reusing the old coil I went through a ton of nitrogen. I had the smallest tank you can rent from a welding supply store and actually used almost the entire bottle. This was to blow out old oil in the system to facilitate a deep vacuum.
I pulled and broke the vacuum 3 times with nitrogen. Pretty satisfying to see it pull down to 220 microns.
You need an inspection mirror to check your work when the system is that low to the ground.
There is some conflicting data on line set driers. Gree says not to use them so I didn’t.
I needed to add 6oz of refrigerant for this system. Double check the valve connection on the can you buy. Mine wasn’t machined properly and the valve core depressor on the gauge lines couldn’t push it down. I am surprised they were even able to get the Schroeder valve in to fill the can.
Since it is dual fuel, we used an Ecobee lite thermostat. What a great option. It makes “heat” your HP and you get another system called “Aux” for the furnace.
I’d give a shout out to AC Service Tech on YouTube. I learned most of what I know from him and can’t believe there are such good videos available.
This is pretty long, so skim for the details that matter to you.
Pumping down the old system:
Trane makes it pretty easy. I run the furnace fan to create a heat load. I close both service valves to make sure they move. Then fully re-open both. I put a gauge with no lines (Amazon) on the service port to reduce refrigerant loss. Press the contactor in (this is dangerous so use your thermostat phone app to run the A/c then pull the service disconnect). It was very easy on this 2013 XR 16 system. Let the machine run for 15 seconds. (Some videos show starting with the high side closed and the machine struggles to start. No point in that). Then close the high side all the way. I watched the gauge go down until it said zero. Closed the quarter turn service valve and released the electrical contactor.
We cut the lines and disconnected the wires. The old unit was 380lbs but moved easily on a regular hand truck with 2 people. The driveway had a ramp on it that made loading it in a truck easy. Watch a video on loading a refrigerator in a pickup and it isn’t as hard as you think.
I was able to trade the old unit to a master electrician who wanted to learn what I was doing in exchange for his help. It was awesome and I got to ask him electrical questions as we went.
Forming the line set:
I started working on the line set extensions. The old vapor line was 7/8. I knew this ahead of time (calipers, outside diameter 0.93”) was able to find a fitting that converted 7/8 to 3/4 which Gree allows. (They also allow a 5/8 vapor line set.) I would suggest getting extra fittings and some 90 degrees even if you don’t think you need them.
The stub of line set I was connecting to came out of the wall at a downward angle to point it where it typically goes for an A/C unit. This is where I wish I had a 90 degree fitting. There was enough room to make a sweeping 90 degree bend in the line set. The bender I had sucked (Amazon). I practiced with it on some scrap line set. It would kink if you went to a full 90, so I spread the needed bends across the length of the line. I also had a spring bender and fully suggest that as a second option, especially if you need to bend in 2 planes. Working with 3/4 line is pretty tough. 7/8 seems like it would be so much worse. The 1 1/8 some units are suggesting now seems like your install time would be 3x.
The 3/8 line I had a nice bender for and it was simple to work with.
After you make all your bends, now you have to flare the pipe with the pipe opening to the ground. I would suggest flaring before putting in the final bend so examining it is easy. I had to examine mine with the inspection mirror and cell phone camera which I didn’t like. I generally plan to flare up to 3 times per line set because I like them perfect. I also have a battery operated flare device (Amazon)so I spend zero minutes being annoyed at having to redo one. I also replace my pipe cutter for every job because they are cheap and a sharp wheel makes nicer cuts. Each cut gets de-burred thoroughly to avoid disturbances in how refrigeration flows as well as line set clean out when they system is replaced.
2 of us slid the unit on the pad. The house was built around 2000 and based on my parents prior landscaping experience with the property, they said the whole yard was professionally graded and mostly rock free. I used 18” long, 3/8” diameter threaded rod with a washer and nut on it to “stake” it into the ground. I pre drilled 1/2” holes through the pad. This wasn’t my favorite way to do this but I didn’t see any other options I liked better besides an extra day and concrete.
I have a giant torque wrench(Amazon BlackMax). A 10 inch adjustable isn’t big enough to fit their flare nuts. It is a good size to use to support the service valve. I pre load my settings the day before so there is nothing to look up or screw up. Memory 1 is the liquid line. M2 for vapor. I did the 3/4” line first. I inspect the brass receiving side to ensure it is clean and the flare for imperfections. I generally start with the low side of the torque range in the manual.
Nitrogen/Vacuum testing:
You need 2 valve core tools. More importantly you need 2 5/16”. A/C use 1/4” typically. I like the Appion Max (Amazon) which are colored pink for the 5/16” size and they feel high quality vs the cheap ones on Amazon. They are $80 each and worth it. Putting the valve core back in is the most stressful part to me and is 100% a “feel” thing. You want to feel the valve click into the core remover when pulling it out and definitely need to feel it catch the threads and fully seat all the way to avoid a leak. I had a valve fall off once with the refrigerant released and had to re seat it blindly floating around in the tool. I have no interest in repeating that. I suggest practicing removing the valve and putting it back a few times when you first remove it (refrigerant still safely in the unit) to get the feel of it.
The indoor coil was 10 years old but looked brand new. It was impressive how perfect it looked. This is why we decided to reuse it. Trane designates a heat pump coil with the letter H 4 digits from the end of model number. A TXV needs a check valve for heat mode to work. The literature on this was a mess. I found one brochure that said the TXV didn’t have an internal check valve. I made a post prior where someone else responded expressing this same concern. I crossed my fingers and hoped Trane wasn’t that annoying to call something a heat pump coil and not come with a heat pump TXV.
Nitrogen side tangent:
People say you don’t need it. Here is my impression of what it is doing. “Nitrogen” is actually dry nitrogen. It absorbs moisture out of the air. For it to dry out the inside of your system, it can only do this if you fill it, let it absorb, flush it through with more nitrogen, let that sit. The oil in a heat pump absorbs water and this degrades its longevity. There are videos online that show this. I'd like to have a system last as long as possible. The second thing it lets you do is pressure test for leaks to the manufacturer specification. Its hard to do that with a vacuum. How to get nitrogen.

1. Go setup an account at a welding supply shop while your unit is in transit. Assume they have bankers hours unless otherwise posted.
2. They will set up an account for anyone. You need the account because you are taking a tank they own and just like the library wants a book back, they want their tank back.
3. You can buy a NITROGEN regulator from Amazon for $50. Don’t buy it for a different gas or it won’t fit the tank. CGA-580 is a typical tank standard.
4. It’s $45 to get a tank. So for ~$100, you can do your install correctly. Obviously this doesn’t apply for Mr. Cool no vac lines.

Rant over.
Reusing the coil created some challenges that offset the ease of not replacing. I blew 100 psi through the unit for a while to try and move the oil from the low spots in the coil. It blows it to the side of the coil tubes more than out. Anywhere there is air or nitrogen between a pool of oil makes pulling a vacuum difficult. I also pressure checked the system at 300 psi. In hindsight the liquid line will have 325psi in it at 85 degrees so I would go to 400 in the future. I couldn’t find literature from Trane that said how high I could go ojn their coil. They say to check at 150psi, but the system will be higher than that when it is off. For example If they would have said 500, I would have done the max Gree says. A vacuum isn’t a leak check no matter what you find on the internet. A vacuum with standard gauges isn’t a vacuum. You need a micron gauge (Amazon $180) and a 1/4” valve to protect it from refrigerant. I used a 3rd core removal tool because i couldn't find a 1/4 valve that didn't look really cheap.
I did my leak checks during the nitrogen test. I go really slow and don't just wipe the blue liquid on, but hold the applicator with a lot of extra fluid on it to the joint so it is fully submerged as I go around the line. It makes it easier to see small leaks. Again time consuming, but worth it.
After a 1 hour stable nitrogen leak check, I slowly removed all but 5 psi of nitrogen. Then pulled a vacuum. The first one didn’t go deep as the oil had settled. So I blew more through and quickly pulled a vacuum before it could pool. I did this 2 more times and pulled a 220 micron vacuum. I open and close the valve core tool valves to ensure no air is trapped in the valve mechanism. On the mini split installs I have done from scratch the only rose 20 microns after an hour. This one rose 70. I accepted for the following reasons:

1. It was gradual. Field piece has a nice video that shows a logarithmic rise (more at the beginning, much slower at the end) is fine if it stays in range.
2. The expected reason it doesn’t fully stop rising is the equipment/hoses/fittings can’t maintain a permanent vacuum that deep.
3. AC service tech showed it’s ok on a new system and seemed unconcerned.

Clearly this was time consuming, but I had baked in extra time to do this.
Refrigerant release:
I disconnected the hoses from the valve core tools. Now was the time to let the refrigerant out. The instructions say to start with the high side. I cracked it open, then the low side. Then opened each a little more.
I put the valve core back in the tool. Once that is screwed on, I burp the lower half of the tool as there is air below the valve.
Now you have to fight the 320 psi to push the valve in and begin threading it. I hold the flat plate with one finger on one hand and turn the plate with the other hand to thread the Schroeder valve.
I was about to add 6oz to the low side of the system when I discover the refrigerant bottle top wasn’t manufactured right and had extra metal hanging into where the Schroeder valve was. I tried to see if I could remove it and couldn’t. It was blocking the opening enough my hoses wouldn’t be able to depress the valve so I had to abandon this idea and will fix it when I have a new bottle.
Leak Check:
At this point I screwed a 1/4” cap with a hole drilled in it on the core removal tool to leak check the Schroeder valve. Again I had to use the inspection mirror because the valve was so low to the ground. I checked the service valves were fully open and placed the caps back on wrench tight. I checked each joint again with the blue leak detector.
Somewhere in the vacuum wait time, I hooked up the thermostat wire. I’m going to leave the details out as some of the wire colors were in use so I used other wire colors. One issue we had was the wire going from the outdoor unit to the indoor unit must have originally been too short so someone spliced in a short extension and then hid the splice. So the A/C wires were connected, but none of the others were. I will probably examine this more in the future during the planning phase. Home Depot sells really nice 10-wire thermostat wire by the foot so if you need extra, it is easy to get.
Electrical Hookup:
The disconnect was still removed from the box near the outdoor unit. The existing power wiring was stranded #6 wire on a 50 Amp breaker. I changed the breaker to a 40 Amp. Mr.Cool wants lugs to connect it vs crushing the stranded wire in the L1/L2/G screw. You can get these on Amazon or from Home Depot.
We secured the flex conduit where it left the wall and where it attached to the unit. They don’t provide pre marked holes for this so we drilled with a 3/32 and put a sheet metal screw in to hold the anchor. We did this for both power and thermostat.
There are 2 small clips inside the outdoor unit on the right wall to secure power and 24v wire separately, a nice touch. Setting the dip switches:
I set the dip switches for a 4 ton unit in energy efficient mode with standard defrost. I initially figured defrost mode was performed by running the fan using the indoor return air to heat the coil. Per the manual, dual fuel fires up the furnace to do it faster.
Startup:
At this point we were ready to start things up. Put the disconnect back in and set the A/C temp low. The control board powered up, various parts inside made soft whirring noises, the the little display said “00” and after about 30 seconds the fans kicked on. I sent my mom inside to see if cold air was coming out and got the thumbs up. We tested heat and it didn't work. We found the wire splice, fixed it an it worked. I also tested auxiliary and it worked. It was quite the relief the TXV worked in heat mode.
Background:
I flew in to do this install so coordinating everything took a bit more work. I did have the benefit my dad has a lot of tools so I didn’t have bring larger heavier items. We shipped stuff in a week before I arrived to confirm everything made it with time to spare. I also bought extra line set for the extension and that paid off in figuring out how good the bender was etc. I probably won’t buy the 1.8 lb R410 tank again (black made my Penn Chem) and rather get the pink 2lb tank that had the green valve and 90 degree 1/4” port.
I’m still amazed at the flexibility of these outdoor units. I like that they can be pumped down for service/retirement and they put service valves on their indoor coil. Thermostat flexibility let us buy a $99 thermostat vs the $700 Japanese brands that don’t have built in WiFi (so they can charge extra for a WiFi module).
The unit is outside the master bath which is just off the master bedroom. They could hear their old A/C. This one they can’t.
I have some angst about the service side of things not living there. I wrote a ton of notes on the inside of the electrical cover that seem pertinent. The fact you can only check charge by weighing it out makes me really hope there are no leaks during its useful life. It seems like recovering it to weigh it would be very expensive and not even accurate as residual r410 stays in the system. It could lead to it being over filled when they weigh the charge back in. If it were to cool less at some point and a leak could be found and repaired, I wonder if you could add slowly with the unit running until the cooling was back to what it was before. What keeps it from getting over charged though if an inexperienced tech just starts adding. How would you ever figure that out without weighing the charge back out.
I hope this helps someone else in the future! Curious to hear from others if there are steps that could have been done betteeasier.
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Bottom off white pipe is leaking, I turned off power to the unit at the breaker. That pipe isn't freon right? Any advice?