New Build Single Furnace/Dual Zone - Upstairs Zone Overheating in Winter (and not cooling enough in summer)

[Anonymous]

This is a 3-level new build. When we set downstairs/middle level thermostat to 73 and upstairs thermostat to 70 the upstairs gets overheated to 80+. HELP. And it's cold in the lower level of course.

We have tried different variations but the upstairs seems to always overheat. We have the same issue in summer.

We plan to call HVAC company but wanted to check here for opinions. Thanks.

[Anonymous]

How open is upstairs to down? A friend's house has no meaningful separation, with a two story foyer/family room and several balconies. Of course the heat rises upstairs. A ceiling fan above the two story space helps mix the air; he never turns his off in summer or winter (generally blowing up to keep it from being too drafty directly below).

[Anonymous]

How open is upstairs to down? A friend's house has no meaningful separation, with a two story foyer/family room and several balconies. Of course the heat rises upstairs. A ceiling fan above the two story space helps mix the air; he never turns his off in summer or winter (generally blowing up to keep it from being too drafty directly below).

Only the foyer is two-story. I understand the upstairs being up to 5 degrees warmer....but it is consistently 10-15 degrees warmer depending on time of day. Crazy. I live on main/middle level of home. Everyone upstairs complains it's too hot...and it is at 83-85.

[Anonymous]

Do you have two completely independent zones (air handlers and all) or are they zoned off a single system? If the zones are in a single system, you may have a zone damper problem, either stuck or improperly installed.

If they're zoned from a single system (or if you're not sure), what happens if you turn on just the hvac fan on both zones at the same time to mix the air? Turn the heat way down so it's just air.

[Anonymous]

I suppose they may have accidentally commingled the ductwork, too, aside from zone dampers. But that would be really weird.

[Anonymous]

Do you have two completely independent zones (air handlers and all) or are they zoned off a single system? If the zones are in a single system, you may have a zone damper problem, either stuck or improperly installed.

If they're zoned from a single system (or if you're not sure), what happens if you turn on just the hvac fan on both zones at the same time to mix the air? Turn the heat way down so it's just air.

It is a dual zone from a single HVAC unit/system. I will try what you recommend tomorrow to see what happens. When you say turn the heat way down...what do you mean? Set the upstairs lower than 73? Thanks.

[Anonymous]

Warm air rises. So the heat from the lowest and middle level are finding their way up, in addition to the heat you have going to that zone. Why not set the uppermost thermostats to 65 or 68 and see if that helps?

[Anonymous]

Warm air rises. So the heat from the lowest and middle level are finding their way up, in addition to the heat you have going to that zone. Why not set the uppermost thermostats to 65 or 68 and see if that helps?

OK...and still set lower level to 73 correct?

[Anonymous]

Fiddling with the thermostat isn't going to fix anything.

What you need to establish is whether the system is malfunctioning, or whether it's working as designed and the design sucks.

Each zone should have what's called a zone damper, it turns the air flow on or off to that zone. In the winter you want more flow to the bottom floor, and in the summer more flow to the top floor. That's what the zone dampers do. On each floor there should be a thermostat that controls the zone damper for that floor. What you need to check is that this is actually happening.

A simple check is to use the thermostats to turn on one zone at a time, and walk around and put your hand over the registers and see if air is coming out. When the upper floor is on and the lower floor is off there should be air coming out of the upper registers and no air from the lower registers, and vice versa.

If the zone dampers aren't working you need the guy who installed it to come back and get them working.

If they are working, and the system still doesn't keep your house comfortable, that's a longer conversation with the installer.

[Anonymous]

Your zone dampers will look something like this:
https://www.zonefirst.com/product/rds/

[Anonymous]

OP here. Would it be ok to just turn off the upstairs thermostat?

[Anonymous]

OP here. Would it be ok to just turn off the upstairs thermostat?

[Anonymous]

Anonymous wrote:OP here. Would it be ok to just turn off the upstairs thermostat?

It's your house, you can do whatever you want.

If the zoning isn't working properly turning off the thermostat isn't going to fix it.

A thermostat is an on-off switch. When the temperature is above the set point it's off, when the temperature is below the set point the thermostat is on. If the temperature upstairs is already above the thermostat set point, the thermostat is already off. Turning it off doesn't make it "more" off.

If the upstairs thermostat is off -- either because you turned it off, or because the temperature is above the set point -- and there is still hot air coming out of the upstairs vents, your system isn't working properly.

[Anonymous]

It's possible that one of your thermostats isn't working and is stuck either on or off. It's super easy to tell if they're working. Look on the thermostat, it tells you the set temperature and the current temperature. When you're heating, if the current temperature is higher than the set temperature the thermostat should be on, when it's lower it should be off. Walk around your house and put your hands over the vents, if the heat is on you'll be able to feel air coming out.

[Anonymous]

Complain to your builder and use your warranty to fix the issues.
In addition talk to your neighbors if they have the same issues.