Hi. A good customer of mine called me because she was having problems with a 3 ton MrCool heat pump that she had a plumber install.
It has 3 heads. It has two 1 ton heads and one 1 1/2 ton head. The only head working (most if not all of the time) is the 1 1/2 ton head. When I arrived I turned on all three heads and all turned on and were working; but, one of the 1 ton heads would not turn back on after it reached temperature and shut off. The other 1 ton head would not shut off.
My customer said the plumber (or a friend of his had come back and added R 410A because it seemed to have a leak. Anyway, the lowside pressure was very low according to my gauges so I ended up adding 6 or 7 pounds of R 410A till the pressure seemed more normal. The next time I came to the job the pressure was way too high. I decided to recover all the R 410 A and weigh in the proper amount. I realized I had over charged it by I think 9 pounds.
I did find a leak with my refrigerant sniffer. My customer acquired another heat pump from MrCool through Home Depot (as a warranty replacement I believe).
Last week I recovered the refrigerant from the old condenser and did my best to pressure test the new hookup to the new condenser. And then I vacuumed (as best I could) the newly hooked up system. MrCool tech support tried to offer advice through this process but seemed to have never walked someone through this before. MrCool systems use line sets that are precharged just like the condensers are and don’t need to be pressure tested or vacuumed down so they don’t really understand why you need to pressure test or vacuum down a system.
Anyway, long story short, I released the refrigerant from the new condenser into the system and added 12 ounces to accommodate the linesets that I believed I had vacuumed down. I turned on all three heads and the lowside pressure which started out at somewhere over 120 started dropping and in a few minutes (2-4) it dropped into a vacuum. Now none of the heads work because the pressure always drops into a vacuum. I checked and made sure I had tightened the lineset connections because if they are not tightened adequately they will not open to allow the refrigerant to pass through and will behave as a restriction.
I’m guessing now that there are foreign particles in the system that are plugging up a txv or txv like device. I cannot check out the two 1 ton heads now to see if there’s any change because the system always goes into vacuum on start up.
At present, the 1 1/2 ton head and the 1 ton head that would turn on but wouldn’t turn back on once it shut off will both turn on but won’t cool because the system goes into a vacuum. The other 1 ton head will not turn on and blow air. It shows the temperature setting and makes a beep every 30 seconds or so.
Tomorrow morning I’m going to put all 3 heads in heat mode and see what happens. I guess I’ll also run the system in cooling and take the top off the condenser (although with the top off the air won’t be going through the coil) and try to locate a cold spot where the restriction is (although it’s hard to get in there and look because of all the crap in the way). If anyone has an idea of what I’m dealing with I could really use some help. I’ve installed a half dozen or so minisplits (Mitsubishi’s and Fujitsu’s) but this is the first MrCool I’ve ever dealt with.