I have a Panasonic Multi Split (Outdoor Unit: CU-2TZ50TBE Indoor Unit TZ25WKEW + TZ35WKEW). It was set up by a certified installer (who is out of business) but I doubt it was correct as how it's currently wired is nowhere shown in the manual. Right now I just want to investigate myself to determine if its correctly or not before calling someone out.

Both units works but the reason I am suspecting something wrong is that when I only have one unit on, I can see that the other unit is also heating. When I look at the manual I can see that the indoor units have a valve, which I suspect are used to shut on/off when a unit is not active. I believe that the indoor units are not communicating properly to these valves, although, it could also be that both the valves are defective.

A picture from the manual shows the following wiring:
Picture from page 66

This is also what it looks like according to Panasonics installation video:
enter image description here

Additionally, in the manual, it shows the following picture:
enter image description here

From the video and last picture, the wiring makes sense when there is one unit. 3 wires to the indoor unit and then 4 wires (1 additional for communication) to the outdoor unit.

My current wiring is as follows:
Power to the outdoor unit (correctly as in the second picture) then 4 wires to each indoor unit. However, I am not sure that the 4 wires to the indoor units are correct. It is wired as:
enter image description here

Where Brown = Power, Blue = Neutral, Black = Communicate, Green = Earth.

This leaves "S1" and "2" empty. But should it really be like that? I think the answer lies in the following picture (also shown above).
enter image description here

From that picture it looks like the neutral (2/N) should be connected to "2" on the indoor unit and not "N".

  • Does it actually work? What's led you to investigate the wiring now? I'd presume it was installed a while ago and that you weren't the last job before the installer went out of business. If it doesn't work (at all? as expected?) what are the "not working" symptoms?
    – FreeMan
    Commented Oct 19, 2022 at 12:45
  • @FreeMan I will update the original post.
    – MLEN
    Commented Oct 19, 2022 at 12:54

1 Answer 1


The wires between the indoor units and the outdoor unit are two power lines, one ground, and a communication wire. You can see in the service manual that the two power wires just go directly over to the input power connection, with no circuitry. If the units are working most of the way they are properly wired, with the caveat that they may or may not be correctly grounded. Improper grounding won't cause operational changes. When mis-wired, these units will usually just blink an error code and refuse to do anything.

Small multi-zone units with three or fewer zones can't have one unit in heat while another unit is in cooling. They should support having one unit on while the other unit is off, so long as they are always in the same mode. If you are seeing the behavior described on page 33 of the service manual, the unit is behaving as expected.

  • I am seeing the behavior described in the manual, I tried putting one unit on cooling and the while the other was heating, it did not work. But I dont believe that the unit is behaving as expected, when one unit is on it is still pushing hot gas to both units, where the unit which is turned of is releasing hot air through an expansion valve.
    – MLEN
    Commented Oct 20, 2022 at 13:59
  • It wouldn't surprise me if the unit that has the fan off still releases a little bit of heat. However if it is a change in behavior you might need to have it looked at, or even have the indoor unit replaced. It is almost certainly not due to a wiring error.
    – KMJ
    Commented Oct 20, 2022 at 14:56
  • KMJ Both units are like this, if units A is hot the other also get hot and vice versa. You can also feel how all four pipes gets hot. I actually tried rewiring and nothing happened, so indeed I dont think its a wiring issue but I do think either the valves are wrong or some issues with the board.
    – MLEN
    Commented Oct 20, 2022 at 15:03
  • Has it always behaved this way? It's usually pretty rare for the same failure to happen close in time on two devices unless there is a serious design fault.
    – KMJ
    Commented Oct 20, 2022 at 15:11
  • Always been like this. Will call out a technican and see what they say.
    – MLEN
    Commented Oct 20, 2022 at 18:57

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