I got an air conditioner installed with 2 indoor units but during the process, we lost track of with line set went to unit A and unit B. The same goes for the electricity cables.

I can't follow where they go as everything is concealed behind walls and ceiling.

The indoor units do start but I feel they are a bit weak, this might be because of the long line set though and we haven't topped it up with gas yet.

The question is though if I would connect the refrigerant lines/electrical lines mixed up, how would the system react?

It is a Panasonic:

CS TZ25WKEW (Indoor) CS TZ35WKEW (Indoor) 2TZ41TBE (Outdoor)

  • You've got wiring A and B, line set C and D and units E and F that were supposed to be connected A/C/E and B/D/F, but that may not be the case? It's possible that A and B were swapped, C and D were swapped, or both? If they were both swapped, you're fine, you just may have the thermostats working the wrong room. If you've swapped the line sets or control lines, well, that probably won't work too well. You'll probably want to trace the control lines, and maybe have an HVAC person draw a vaccume on the line sets to see which is which.
    – FreeMan
    Oct 19, 2021 at 12:20
  • @FreeMan I have indoor unit A and B, which needs to be connected to A and B slot of the outdoor unit. So either they are connected A-B or correctly (A-A, B-B). If they are incorrectly connected, switching either the refrigerant line OR electrical wires should be enough. Switching the electrical is much easier...
    – MLEN
    Oct 19, 2021 at 13:47
  • 1
    This should be easy to identify with a voltmeter for the control signals and touch to tell which coolant line is active.
    – Jeffrey
    Oct 19, 2021 at 17:29

1 Answer 1


I'm no HVAC expert. The following is based on reason and common (to me) sense:

how would the system react?

I would presume that if you've got line set A connected to an interior unit to which you've connected the electronic controls for unit B (and vice-versa), at best you're going to get very limited cooling and in the wrong place. It's quite likely, though, that the outdoor unit will be pumping refrigerant through a line set connected to a currently inactive indoor unit and that indoor unit will end up freezing up because there's no fan running to blow warm air over the fins and exchange heat.

With frozen lines, you'll get very little cooling at all, and possibly damage the indoor unit, the line set and outdoor unit should lines split somewhere.

I would suspect (remember, I'm no HVAC expert, this is applied reasoning), that if you were to turn the system on and crank the AC up in one room, you should be able to hear the outdoor unit kick on, then start to feel cold air move in that room. If things are cross-wired, you might notice a slight cooling, but you won't feel the air moving. If you feel it blowing warmish air from the other indoor unit, you know you've got the wiring crossed. If it's crossed, shut everything off (at the breaker and/or disconnect) swap the wiring at the outdoor unit, and all should be good.

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