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4 head mini split heat pump system help

andrewxxi Member Posts: 2
I recently intalled a 4 head mini split heat pump system. Inverter flex in the brand. The issue I am having is that I can't get one of the units to blow heat. When I run the three others they heat just fine. When I try and run that one it puts on the outdoor unit but when the indoor unit blower kicks on it just blows air. No heat. I have ran they all together and Individually. I have tried tech support but can't get through when I am on site and they are only available on normal business hours.


    JUGHNE Member Posts: 10,278
    edited December 2015
    I have installed 3 head units. The outside unit had 4 connections available but of course I only used the 3 needed. The fourth was oversized connections. It wasn't clear in the I&O manual but it seemed that the 4th could be used if one of the other 3 were not turned on. Such as the 4th would be a meeting/conference room seldom used. The outdoor unit didn't have the capacity for all 4.
    This is a rationing concept that works in Europe or Asia, maybe not for us here. We want it all! This was some years ago, you should check your I&O manual.

    When you say you have run them individually but they won't all 4 work. Did you shut one of them off completely rather than just turning them down on the t-stat?
  • andrewxxi
    andrewxxi Member Posts: 2
    There is one that no matter what never blows heat. Even if I try and run it by itself. And it's only that head that I am having an issue with.
  • hvacfreak2
    hvacfreak2 Member Posts: 500
    You might want to check that everything is connected on the indoor unit board. Those small connectors can get bumped from the sockets ( or not plugged in from the factory ). Especially the wall hung type , not much room in those.

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

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  • njtommy
    njtommy Member Posts: 1,105
    edited December 2015
    What brand is the unit?
    Also what's the model number?
    JUGHNE Member Posts: 10,278
    So the problem unit, has 240 VAC because the inside fan runs, tells the outside unit to start, (Are the compressor AND ODF both running?)

    What does this do if you can put the system to cool?
    Maybe rev valve or exp valve malfunction.
    If you can exercise the reversing valve maybe something will change.
  • ratio
    ratio Member Posts: 3,332
    Is this the style with one compressor & branches on the refrigerant piping, or four compressors & four sets of refrigerant teats? If there's only one compressor, it shouldn't be possible for one head to not heat if the system is heating, unless there's a valve inside the head. Check for a restriction in the lineset?