We have a three zone Mitsubishi ductless system installed by a Diamond Certified installer. The compressor is a MXZ-3C30NAHZ2 and we have two 9btu and one 12btu MZS-GL interior units.
Here's the problem:
The downstairs unit is set to 74 degrees, because we like that room warm
The bedroom units upstairs is set to 64 since we like that room cooler
The den unit upstairs is set to 69 and is in a very sunny room that get's very hot, so we expect this unit to only come on at night on cooler nights when it gets cold
What we find is that since the downstairs unit on the first floor is running often to keep the room at 74, the upstairs units are almost always blowing hot air even when the temperature in the room is way over the set point (only one green light on, so not heating it but it is still very much "heating"). The bedroom hovers at about 74 (with a 64 set point), and the den was 85 the other day (set point 69) while the unit was blowing hot air. I've had to run around and turn on/off units to avoid zones getting too hot. I'm worried the inverse will be true during cooling season.
I thought this was a multi-zone system, but if I have to turn units on/off to manage temperatures in different zones, how does that achieve multi-zone? All the marketing materials for Mitsubishi multi-zone are about "everyone get's to personalize the temperature to what they prefer" etc.
So, I'm confused.
I was wondering if anyone understands this problem and can help me understand if:
1) there is maybe something wrong with my installation or
2) there is something wrong with my understanding of what mult-zone means?
Thanks!
Here's the problem:
The downstairs unit is set to 74 degrees, because we like that room warm
The bedroom units upstairs is set to 64 since we like that room cooler
The den unit upstairs is set to 69 and is in a very sunny room that get's very hot, so we expect this unit to only come on at night on cooler nights when it gets cold
What we find is that since the downstairs unit on the first floor is running often to keep the room at 74, the upstairs units are almost always blowing hot air even when the temperature in the room is way over the set point (only one green light on, so not heating it but it is still very much "heating"). The bedroom hovers at about 74 (with a 64 set point), and the den was 85 the other day (set point 69) while the unit was blowing hot air. I've had to run around and turn on/off units to avoid zones getting too hot. I'm worried the inverse will be true during cooling season.
I thought this was a multi-zone system, but if I have to turn units on/off to manage temperatures in different zones, how does that achieve multi-zone? All the marketing materials for Mitsubishi multi-zone are about "everyone get's to personalize the temperature to what they prefer" etc.
So, I'm confused.
I was wondering if anyone understands this problem and can help me understand if:
1) there is maybe something wrong with my installation or
2) there is something wrong with my understanding of what mult-zone means?
Thanks!
source https://hvac-talk.com/vbb/threads/2228776-Mitsubishi-multi-zone-ductless-units-not-respecting-set-point?goto=newpost
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