Mitsubishi Mini Split Branch Box Location

rwk

I have a 5 zone mini split being installed in my house. The branch box is to be located in the attic. However I noticed this verbage in the installation manual “ Do not install the branch box in location that is hot and humid for long periods of time “. I live in Missouri so it gets really hot in the attic even on 75 degree days. I asked my dealer about it and he said that is where they always mount them. Is this common practice? Is there any short term or long term problems that will be caused by this type of installation?

Tinman

I’ve installed only 2 systems with 5 zone branch boxes. I didn’t put either branch box in the attic. I could see how it would be easier to get the refrigerant lines from the B.B. to the heads but I like to follow manufacturer’s instructions wherever possible. Have you asked the contractor what other options are available in your home?

GBart

Right it states: "Do not install in location that is hot or humid for long periods of time."

Which begs the question just what is a long period of time?

The factory knows it's going to affect performance, so will extreme cold, the only ones I've worked with have been in office buildings in the overhead which is temperate, from what I've heard most guys are insulating these when situations like this arise.

The manual also states: Conduct sufficient anti-condensation and insulation work to prevent water dripping
from the refrigerant piping. (liquid pipe/gas pipe)
• Increase insulation depending on the environment where the refrigerant piping is installed, or condensation may occur on the surface of the insulation material.
(Insulation material Heat-resistant temperature: 10 °C, Thickness: 15 mm or more)
* When the refrigerant piping is used in locations subject to high temperature and humidity such as in the attic, further addition of insulation may be required.

ratio

With Mitsubishi, the branch box is more than a collection of valves that distribute the refrigerant. It actually has a little condenser in it to make liquid refrigerant for certain operating modes and it needs a condensate drain. I imagine that Mitsubishi doesn't want it outside the envelope because of that.

GW

The B.B. needs a drain?

If I had to put it in an attic I would figure out a way to insulate it very well

Tinman

The branch box on a Mitsubishi, as far as I know, does not require a drain. I think I would have lost some ceiling tiles on this one that was installed 2 years ago if it did.

rwk

Thank you for your responses. There is a crawl space in my house. I think by your responses that I should look into mounting it there. It is not a air conditioned space but it has a dehumidifier. The biggest obstacle will be getting the lines for the two ceiling cassettes down to the branch box. Thanks again.

ratio

I guess it's time for me to read over the paperworks again, <sigh>

ratio

I guess there are different models of branch boxes. This one has a drain, I'd not want it outside the envelope unless absolutely necessary.

GW

hummm how old is that install? i think the older BB systems had a drain, but i'm not sure. We have done 3 bb jobs in the last 2 years and neither had a drain.

ratio

Started to vac the system yesterday in prep for adding 61 lbs of field charge. They're the true heat recovery boxes, maybe that's the difference.

GW

61 pounds? what kind of system?

ratio

Big CityMulti system. 7 heads on this condenser, double wide 8 ton unit looks something like this. Down 4 stories to the branch selector, longest runout from there is IIRC about 120'. The other CityMULTI only needs about 40 lbs of additional juice. The field charge is cyphered up by Mitsubishi's Diamond Builder software. after you punch in the field measurements of the linesets.

GW

ahhh didn't know we were talking City. sounds like a big job, i hope you can make some dough

ratio

Making money is someone else's problem. My job is to not screw up the install too bad.

Huh, yah, maybe a CityMulti branch box isn't the same as a mini split branch box, I've never installed a mini split with a branch box, just the models with the multiple teats on the outside unit.

hvacfreak2

The CM VRF box is called a " BC Controller ". The box does have a drain to comply with IMC and local codes however will never see a drop of water more often than not. I have many out there outfitted with condensate pans , pumps , pan switches just for looks ( they collect more dust than condensate ). The Mr. Slim " Branch Box " may perform some of the same actions as a BC but it is not the same ( if this wasn't clear throughout the thread ). The pans do come in handy for the BC Controllers as they will show any oil that can leak from the 32 ( on a 16 port ) closely spaced flare connections.