new Mitsubishi mini split install with weird issues

bostonapt · May 30

So I just had some mini splits installed in my house.

I have 9k(small bead room) and 18k(living room) on one compressor. 15k(basement) and 12k(bead room) on one compressor.

Both heads connected to the same compressor will be set to 72 and one head will will output cold and the other one will output zero cold and the fan will only blow. I will have the unit set to 72f and it will get the room to 65 if I allow it to keep running. If I try running the 12k(bead room) but not the 15k(basement) since it is already 70 in the basement then the 15k(basement) will form ice on it unless I leave it on at least dry mode. The problem is the basement freezes up and the 15k(basement) I feels like only the fan is rotating becuase I feel zero cold coming out.

What is going on? Is this fixable?

EdTheHeaterMan · May 30

You could have the heads connected wrong. The head connected to refrigeration lines A may be wired to electrical connection B and the head connected to refrigerant lines B may be wired to electrical connection A

This would cause one zone to not cool at all, and the other zone to over cool because the refrigerant is going to the wrong head.

ratio · May 30

Sure sounds like the heads are wired backwards to me as well. If the wires follow the linesets and they are easily separated any place they come together, you may be able to determine this yourself, just see if the labels on the pipe ports and wire terminals are the same (A, B, etc.). It is a rather easy mistake to make.

The installer should come out and do this for free if you call them and tell them the systems aren't working properly.

yellowdog · May 31

What model numbers are your condensers? These are combinations that I would not combine onto condensers. You are getting some serious derating with these combinations unless they oversized the heads to account for it.

GW · June 2

crossed wires, it happens!

bostonapt · June 7

Update

Yup the installer managed to cross the wires on both compressors. Seriously label the wires already. I thought I was looking my mind because none of the rooms would stay at their set temperature, but crossed wires makes sense now. I just though they sucked at first.

It was extra weird because the installer fixed one side then kept saying that the other side just needed to be reset and was fixed now, what ever that means and left. Then I tested each unit with the other unit off and opposite head would get hot/cold. I finally after some convincing got them to finally untwist the second compressor the next day. I would hate to see what wold happen if more then two heads where hooked up.

ratio · June 7

https://forum.heatinghelp.com/discussion/comment/1803455#Comment_1803455

If my experience is any indication, you chase a frozen head for a week or two, then call me. 😉

GW · June 9

Glad it's all good

"just label them"—- we do label them, but then the label doesn't fit through the 'wire connectors' at the outdoor unit. So we remove the labels. It's seems so duh, I know.

new Mitsubishi mini split install with weird issues

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