Mitsubishi air handlers on same branch box unwanted heat.

ahallasjr

I have 3 air handlers on the same branch box. With only 1 room thermostat calling for heat, the other 2 which are NOT calling for heat, because the their room set points are way below room temp, are warming up. This in turn warms up their rooms. I'm told the valves in the branch box when in the heat mode never close all the way. Is this normal?

GW

Three air handlers on one box, curious. What size units? Small units I suspect 

It’s expected to bypass some hot gas into idle zones. Are you saying the blower is pushing air? The blower should not be on. 

How big are these rooms?

curious, what controls are you using? MHK2? 

ahallasjr

Gary, Here is a list of my equipment.

MXZ-4C36NAHZ-U1 Heat Pump
39,554 BTUs Cooling
42,633 BTUs Heating
19.1 SEER, 14 EER, 11.3 HSPF

Branch Box 1 PAC-MKA32BC

Living Room
Wall-Mounted
MSZ-GL12NA-U1 S/N
11,718 BTUs Cooling
14,273 BTUs Heating

2nd Floor Suite
Floor-Mounted
MFZ-KJ09NA-U1 W/MHK2
CONTROLLER INCLUDED.
8,788 BTUs Cooling
10,903 BTUs Heating

3rd Floor Bedroom
Floor-Mounted
MFZ-KJ09NA-U1 W/MHK2.
CONTROLLER INCLUDED
8,788 BTUs Cooling
10,903 BTUs Heating

The 2nd and 3rd floor use MHK2's and provide heat even though the set points are far below the room temps. The fans are NOT running. The vanes are open and they are acting like radiators, causing unwanted heat.

ahallasjr

Gary,

Living Room. 550
2nd 550
3rd 300

Approx.

GW

Makes sense, when you said air handler I thought of something else.

That’s a very routine installation.

Multi zones will always shoot some hot gas/energy, especially when it’s not super cold outside.

The smaller the room, the more noticeable this overshooting effect will be.

The lowest capacity on that unit is roughly 30%, so, this time of year, it’s extremely hard for that outdoor unit two run a good healthy cycle and not create some excess energy.

you have a 12 and two nines. your outdoor unit is a little bit on the big side.

I always try to promote single zone systems. A lot of people don’t wanna have a number of units sitting outside their house. we have one house with 10 units sitting outside, and a month ago we did a house with eight units sitting outside. It’s a little busy, but similar zone systems are the best performance

Gary 

ahallasjr

Gary, I’m a novice, so thank you for sharing your expertise….