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Mini split dual zone- Does refrigerant circulate to heads that are powered off?

Mitsubishi mini split with two zones. In heat mode. Main room head is in heat mode, bedroom head is powered off with remote. Is refrigerant supposed to be flowing to a powered off head? Is there a solenoid valve that is supposed to shut refrigerant flow off from heads that are not calling for heat? Audible heat expansion clicks, creaks detectable though head is powered off with room remote. Also I think it is heating the room up, though the fan is not on. ( creaks and clicks much more when powered on)


  • pecmsg
    pecmsg Member Posts: 4,704
    No solenoid valve but a EEV instead. 
    Yes if the 1 head operating can’t handle tee load then it allows some bypass. 
    Agai very important to have it sized properly to minimize these issues. 
  • ncmeter
    ncmeter Member Posts: 2
    Thanks for your comment. May I ask then, how would incorrect sizing of the system cause the room that has the heat turned off to receive heat? Would there be an Eev for each line set/ head? Does it operate in a similar fashion to a circulator with zone valves?
  • GGross
    GGross Member Posts: 977

    The load of the space that is in heating mode is less than the minimum capacity range of your outdoor unit, likely the system sees this and allows the inactive head to function a little bit. At least this is my understanding of multi head systems though I deal mostly with LG not mitsu but similiar enough. Multiple head systems generally are not designed to have all but one head turned off, though it does happen on occasion.
  • dirtbike59
    dirtbike59 Member Posts: 8
    I have Mitsubishi hyper heat units. 3 heads to one outdoor 18-6-6. When heating none of the heads fully shut off. If my 18k head runs hard it will over temp the other rooms with the 2 6k heads. Even if I have a head off with the remote you’ll still feel heat above it. I was told that the best I can do is get the wall thermostat for it and there’s a setting to stop the fan and close the vents when no heat is being called. Or should of done 2 outdoor units. 
  • TAG
    TAG Member Posts: 755
    Some refrigerant flow to all the heads occurs even when a head is off. It has to ....

    Installers don't understand the multi head systems .... I have run into this over and over. All too often they match the outside compressor size by adding up the inside heads vs doing a load and matching the outside size to the load.

    You don't really want to have heads "off" -- the idea if for the multi systems to be managing the heat and cool loads with some reasonable setbacks for the different spaces. Every compressor has a minimum output -- if the minimum out put is 12k for a 36k unit and it only running to a partially needed 12k head .... think about it ?

    I have done multi and they work great when designed properly -- working to cool and heat a space like a zoned ducted setup. Not ideal when mismatched to oversized compressor and head off.

    Also -- there are tables that explain what heads can be connected to what compressors and what the heads will deliver. A head on a multi and a single will have different output numbers even though the heads are the same. You can also have more heads than compressor -- I have two setup with 3x 12k heads on a 30k compressor .... doing that load is most important