Testing a Mini-Split

[Allan Dozier]

Seems like HVAC has been a popular topic lately. I have two questions. I have installed a single head Mini before and it went well. I am now installing a 3 head unit in a rental house. The outside unit has the 3 high and low fittings for each of the 3 inside units as expected but there is also another service port on the suction side above the set of 3. So I assume I need to nitrogen pressure test and deep vacuum each of the 3 circuits individually? What do I do about the bigger service port at the top? It seems to me that the one up top doesn't go anywhere much other than to the accumulator and I assume is already charged with refrigerant. The installation manual makes no mention of course. The second question concerns the adapters sent with the unit, It is a 12/9/9 BTU unit and the suction flares on the outdoor unit are 3/8. The line set for the 12K head is 1/2" suction. They sent 3 adapters: 3/8 to 1/2 flare which would be used for the larger line set. There is a piece of flared copper tube inside the adapter. I assume that this stays in place so that there is soft copper between the brass flare surfaces. But I have never used one of these and wanted to make sure it wasn't there just for their testing. Thanks.

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[Bill George]

Sounds like a good question for the people who sold this to you. The larger ones to the left I would guess are service ports to the main common header inside. Those flare adapters are another source for leaks. If you were capable of silver or Sil Phos brazing I would do the adapters that way.

[Allan Dozier]

Thanks Bill. Sorry the photo is turned on its side. I think I will call the Ductless Aire company and give it a try. I ordered it through Lowes but the paperwork says No License, NO Support. It seems to me like if I pressure test each of the 3 zones separately then that should test all 4 of the flare connections on that zone even if I don't open the service valve with the hex wrench. Then once all 3 zones are pressure tested and vacuumed I could then open the upper (left in the photo) master service valve and all 3 individual valves to release the refrigerant. If I can't find the information I think I may open the case and try to see how all the pipes and valves are manifolded to figure it out.
Here is a video put out by Cooper and Hunter which says you can do it all through the master valve but could do each zone individually if desired. check at about 8:20

https://www.youtube.com/watch?v=Cxuiytm_CMo

[Bill George]

Thanks Bill. Sorry the photo is turned on its side. I think I will call the Ductless Aire company and give it a try. I ordered it through Lowes but the paperwork says No License, NO Support. It seems to me like if I pressure test each of the 3 zones separately then that should test all 4 of the flare connections on that zone even if I don't open the service valve with the hex wrench. Then once all 3 zones are pressure tested and vacuumed I could then open the upper (left in the photo) master service valve and all 3 individual valves to release the refrigerant. If I can't find the information I think I may open the case and try to see how all the pipes and valves are manifolded to figure it out.
Here is a video put out by Cooper and Hunter which says you can do it all through the master valve but could do each zone individually if desired. check at about 8:20

https://www.youtube.com/watch?v=Cxuiytm_CMo

These units were intended to be installed by skilled HVAC people with the CFC background to handle refrigerants. These units are pre-charged with the proper amount of refrigerant. The lines are intended to be installed, pressure checked and then vacuumed out with a good vac pump and then the refrigerant released via those closed off ports. Did you happen to check their website? https://ductlessaire.com/support-videos/

[Allan Dozier]

Yeah, I looked at their website but I didn't see anything concerning multi-zone testing. I found it interesting that they just linked some of Craig's videos from ACServicetech. He is excellent BTW. I have all the benders, eccentric flaring tools, electronic leak tester, torque wrenches, SuperBlu, several gauge sets, micron vacuum gauge, several valve core removal tools, vacuum pump, scales, etc. since I have had a 609 certification for a while.
Actually am taking the 608 exam next week since I foresee I may need to buy more 410A in the future. I have plenty of 134A, 404A, and some 12 still. I thought it best to go ahead with the universal certification since I own 26 HVAC units, 11 refrigerator, 4 freezers, and a large walk-in cooler. So it seems like I am always needing to do something with them and my buddy who did my HVAC work since 1988 is retiring.

[Tom M King]

Allan, you sound a lot like me, but I only own 7 heat pumps and one mini-split. I didn't install the mini-split, so sorry I can't offer any first hand advice on that. Our mini-split was installed by a pro, and it did leak. Ones installed by my scientist friends themselves have had no leaking since using these

https://www.amazon.com/dp/B07M81FBF9/?coliid=I7N4AJL9AAGP9&colid=2P8GBP5SU4LS7&ref_=lv_ov_lig_dp_it&th=1

Ones they had installed by pros also leaked down before learning about this work themselves, same as me.

It seems like flare fittings are standard on mini-splits.

Pros around here are unimpressive as well as expensive.

Good luck, and please keep us posted on your progress on this. I foresee more and more people starting to do this themselves.

[Allan Dozier]

Thanks Tom. I've been reading your posts for a while and thought the same thing. Too bad we aren't a couple hours closer, I bet we could help each other out frequently and borrow each other's stuff.

[Tom M King]

Sounds like fun to me, but I can't get more than a couple of hundred yards away from home, needing to stay close to care for my half paralyzed almost 107 year old Mom.

[Tom M King]

Allan, I'm having trouble with PM's, so am putting this picture here since I expect you'll check this thread. This is compost that is full of worms. We have a place where I've been letting surrounding lake lot owners dump leaves for over 40 years, as well as stall cleanings from when we had horses staying in the barn for a couple of decades. I had an excavator pile some of it up, with intentions of getting someone to come screen it. Long story shortened, I'm going to end up building a screen myself.

I'll need a lot of it, but otherwise it's a shame you're so far away.

[Bill George]

Flares are a very poor way of connection for R410A units and this is from a guy who has done non leaking flares on commercial units for 30 years. Way to much pressure for that refrigerant. The Mr. Cool setup is much better for the DIY installs.

I would much prefer silver brazing or Sil Phos connections as I know 100% I will have no leaks on my fittings. In fact I looked into ways to do that on my job.

But even a lot of residential pro's can not braze or flare connections either, and a lot of those "Techs" are self taught seat of the pants folks who screw up a lot of installs. Mini splits are way above their pay grade!!

The brand I used was recommended by my son who runs commercial service tech crews and they have next to zero call backs on the Mitsubishi.

[Allan Dozier]

Thanks Bill. I think I could braze it successfully but admit I say that only by having soldered multitude of copper plumbing and air lines. I have oxyacetylene and have already obtained the 15% silver rods in anticipation of possibly having to extend one of the linseeds. I have swaging tools too. I'll see what the pressure testing and vacuum decay shows maybe first but will be prepared to braze then.

[Allan Dozier]

Allan, I'm having trouble with PM's, so am putting this picture here since I expect you'll check this thread. This is compost that is full of worms. We have a place where I've been letting surrounding lake lot owners dump leaves for over 40 years, as well as stall cleanings from when we had horses staying in the barn for a couple of decades. I had an excavator pile some of it up, with intentions of getting someone to come screen it. Long story shortened, I'm going to end up building a screen myself.

I'll need a lot of it, but otherwise it's a shame you're so far away.

Wow, that is like gold to an organic farmer! I have a dump trailer but it only holds 2 to 3 yards so the diesel expense would be prohibitive. Wallace farms is in north Charlotte who supplies potting soil etc. to Lowes and I have gotten a few loads from them but we really didn't save all that much money over the bags. We let a landscaper dump leaves at a spot on our property but it takes a long time to decompose apparently. I don't have time to aerate it properly with the tractor which would probably help.

[Tom M King]

I've not seen a lot of mini-splits, but I've never seen anything but flare fittings. I do like the idea of brazing the lines on the inside unit though, since some shoving if involved in getting it into place.

https://www.acservicetech.com/post/can-you-braze-mini-split-systems-instead-of-flaring-them

I could go in the fishing worm business with that compost, but the to-do list is already out of hand.

[Bill George]

Flares were fine when they ran R22, but the skill level is such on the mini split installs, how many of the ??Techs?? can solder (without leaks) let alone silver or Sil Phos braze. The skill sets are just not there, that's why the Mr. Cool units type pre-charged line sets are the wave of the future for DIY and many of the techs in the field.

[Jack Frederick]

Whichever method you choose, flare or braze, practice, practice, practice. Once decent on the bench practice it overhead. It is different especially if you have some years on you and your bifocals don’t work looking up. To the comment about having to much to close the unit onto the mounting bracketI try to avoid this by moving the drain line to the left side leaving only the line set and power line under the unit.
If you flare pay attention to your flaring tool. When the 410a units came out it was suggested that I get a new flaring tool. I bought the Yellow Jacket tool and the first time I used it I took my standard plumbing flaring tool that I had for about 40 yrs and threw one part in one trash barrel and one in another so they would likely never be used again. The YJ was excellent. Then I found that it was not holding the 1/4” line securely. Currently I use the Hilmor Orbital unit. I hear that the Ridgid units are good as a well, but have no experience with them. The Hilmor was pricey, but it only takes one leak….

[Tom M King]

While flare fittings are not ideal, there are many tens of thousands of them holding in mini-splits all over the world. If you are going to do any, watch the video I linked to earlier. Without line stubs on the outside unit, it looks like brazing is out of the picture.

I could never get excited about any of the manual flare tools, but do like the Navac NEF6LM. The thing I was most impressed with, when I first picked one up, was how smooth the flaring cone was. I'd rather it was corded than cordless, but it's not available without the battery power.

https://www.youtube.com/watch?v=4SU_lxETtbk

https://www.trutechtools.com/navac-nef6lm-cordless-power-flaring-tool-max-od.html

My Scientist friends and I went in together on some of the HVAC tools. The list of people I will lend tools to is Very short. They have installed four in the last couple of years, and all work flawlessly. It's not the method of how a system is configured, it's how meticulous the installer is.

I will have a couple to install this Spring.

edited to add: My friends bought this setup after installing their first one, and it looks like it's worth having. I may even recover the refrigerant out of the unit in my Mom's suite, and take the inside unit outside the next time it needs to be cleaned. I don't like the circus involved in cleaning one inside, or else I'm going to come up with some kind of container rather than a bag with drain.

https://www.supplyhouse.com/Rectorseal-97705-Mighty-Bracket-Mini-Split-Installation-Support-Tool

[Bill George]

I believe we are the only country that has banned R22 so the rest of the world may be using that and it operates at 100s of PSIG less than R410a. Europe may be using hydrocarbon based refrigerant kind of like propane, again lower pressures. I have a wonderful Rol Air flaring tool I have had for35 years or so, but the flares on my unit that leaked.... were factory.

Last time I cleaned my Mini I said there needs to be a better way This > https://www.amazon.com/dp/B083S85X97/?coliid=I1ZHEDC33FU3NT&colid=18ZVQ88FEDA3X&ref_=lv_ov_lig_dp_it&th=1

[Jack Frederick]

Yes, R22 operates at less than pressure but also much less efficiency. My R22 Fujitsu’s were in the 13 seer range. I installed a 12kbtu in our family room in ‘06, the first year the inverter 410a units came out. It was 25 seer and 12 hspf. It is a stunning performance difference. The unitary guys ( Carrier, York, Lennox, Trane, etc) still do not approach those numbers

[Tom M King]

I think we're still in the early days of mini-splits. They have computers that control fan speed, compressor speed, and even amount of refrigerant that the system uses at any small amount of time. With all that internal brain power, there seems to be almost a complete void in troubleshooting. They should have a port to plug into the electronics on them that displays codes for problems like all cars do now. It hasn't been so long that such a plug in computer works with ECM motors for reasonable cost.

Also, the way the accumulator works, you can't easily adjust for the best amount of refrigerant in the system like you can with regular single speed heat pumps.

The efficiency is many times better, but the possibility for troubleshooting has lagged behind. About the only way to make sure a mini-split has the best amount of refrigerant in it is to recover it all, and put it back in by weight. Put in too much, and you'll ruin a compressor by guessing wrong.

The flare ends are old school for such a new type system. I foresee good changes in the not to distant future, and am reluctant to invest in current technology. I do need to put in a couple of them this Spring though, so hoping we'll see some changes before then.

[Jim Becker]

I think we're still in the early days of mini-splits. They have computers that control fan speed, compressor speed, and even amount of refrigerant that the system uses at any small amount of time. With all that internal brain power, there seems to be almost a complete void in troubleshooting. They should have a port to plug into the electronics on them that displays codes for problems like all cars do now. It hasn't been so long that such a plug in computer works with ECM motors for reasonable cost.

I completely agree with this and given most mini splits these days have an app that can be used to control them and look at "statistics", be they ever so terse, I don't understand why the manufacturers don't incorporate more detailed performance information data flow from the multiple processors in these systems. The actual control and smarts of current generation systems is outstanding so it would be nice to have equally outstanding feedback.

[Allan Dozier]

This guy, Craig, usually provides a clear and concise guide and has a great website. I have his book on charging but he just came out with a new book on mini-splits. I am too cheap to buy it right now but may if I run into problems. I was planning on waiting until some used copies came out.

https://www.acservicetech.com/mini-split-book (https://www.acservicetech.com/mini-split-book)

[Tom M King]

I have his book too, and highly recommend their channel on youtube. I will often refresh my memory with one of his videos if it's a job I haven't done in a good while. Another one that is also worth some time is HVAC school channel on youtube.

It's not that hard to troubleshoot one now, but it requires a number of different tools, and some guesswork to start with, which could greatly be simplified with onboard diagnostics.

https://hvacrschool.com/

edited to add: Even refrigerators, washers, and dryers now display a code to tell you what the problem is. My personal favorite was one night at Dinner at a friends house when their refrigerator displayed a FU code. That one was good for a lot of laughs.

[Allan Dozier]

Tom, as far as the support tool you linked, I made a very, very rough substitute with some scrap. It does help to hold the unit while you are hooking it up but also it allows me (depending on the location of the mount) to keep the flare joint exposed to leak test. If ok then I put it on the bracket. This photo got rotated 90 like the other one.
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[Tom M King]

That looks good. If I just had somewhere to store more stuff. The little metal arms store in not much room.

[Tom M King]

Here's a good video on installing regular lines on a mini-split with good tools. This is an older version of the Navac cordless flaring tool. Since I'm working on them at home, I leave the nitrogen pressure test on overnight.

https://www.youtube.com/watch?v=TOzZ4wa0YUM

Here's a pressure and temperature chart for Nitrogen. If the temperature changes overnight, the pressure in the lines will also change. This will give you something to see what the difference you might see overnight is. https://icemeister.net/backroom/calculators-2/nitrogen-pressure-vs-temperature-calculator

[Allan Dozier]

Thought I would update this in case other members run into the same situation with multi-zone mini-splits. I pressure tested each of the 3 zones separately with nitrogen and evacuated each separately down to less than 200 microns. Only then did I open the valves to release the refrigerant. I did the zones first and interestingly I could hear a small flow when I released the first even though I had not opened the master valve up top. I then opened both of the master valves and definitely heard the refrigerant enter the manifold. All 3 units are working well. Although some sources said they just used the master valve for testing, etc. I can confirm that doing each individually works.