branch boxes for multizone ductless heat pump
Hi, I have been looking at the submittal data sheet for certain models of Mitsubishi “hyper heat” compressors. We live on border zones 5 & 6 (VT-MA stateline). We are considering heating part of the house with ductless heat pumps. In the part where it shows how many indoor handlers the compressor can serve, it gives a certain number if no “branch box” is used versus a different number if there is indeed a “branch box”. I do not work in hvac so have no idea what a “branch box” is, nor under what circumstances it’s prudent to use one. When I googled it, I came across a couple forums (not GBA) in which confused homeowners complained that one vendor had recommended heat pump install with branch boxes while a different vendor stated branch boxes were a poor idea. Can someone please explain to this layperson: what is a branch box? How do I know when it’s good to have one? There is only one Mitusbishi “diamond dealer” near me, and they: a) could not figure out how to duct my house and b) gave me a quote for a very very very oversized system after I provided them with a meticulous manual J that I had completed in Wrightsoft. For this reason, I do not trust them. Hoping a kind GBA reader with hvac background might explain…? Thanks
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The larger multi splits only have two refrigernat ports. You need something to distribute the refrigerant to the multiple indoor units, that is what the branch box is for. The smaller multi splits with many ports essentially have the branch box built in.
Where it gest confusing is the newer Mitsubishi SM units. The SM series have SM specific indoor units which have all the branch box smarts built in so you can hook it up to an SM outdoor unit simply with a bunch of refrigerant splitters. This allows for much higher number of indoor units to be connected to a single multi split. You can still put a branch box on an SM and use the "normal" indoor units but you will only be allowed to connect fewer heads.
Thank you, Akos. Is it fair to say that, on a "large" multisplit (maybe 3 ton and above?) if Im connecting to more than 2 heads, I will need branch box, whereas if 2 or fewer heads, no branch box is needed? And for the Mitsubishi SM units (which run from 3 ton to 5 ton, from what I can see), branch box is optional but not necessary?