One zone only runs when other zone running?

[rblakenyc]

I received such great advice on my first problem I decided to ask about my second.

I have a 4600 sf house running off two a/c's and furnaces - one for upstairs and one for downstairs.

The upstairs has two zones (at least I think that is what it means when you have two thermostats?) and presumably a damper in the attic (again?).

In my experience, the a/c (and perhaps heat but certainly a/c) only runs for the play-room over the garage zone when the main zone (master bedroom) is triggered and running.

I hope I have defined the issue accurately. How would a tech investigate a problem like this - do they have to go up to the attic?

Thanks for advice or questions!!

Rick

[beenthere]

May be wired/set up as a slave zone that can only work when the other zone is calling.

A 2 zoned system would have at least 2 dampers. 1 for each zone.

[rblakenyc]

Thanks been there, would be some reason to do that? I'm not sure why that would be good.

Is it possible it is just a damper problem? (I'm totally shooting in the dark.)

[beenthere]

Done sometimes to make sure a zone that is too small doesn't harm the furnace.

Not a damper problem, since it does work. more of a setup problem, wiring problem, or as said earlier, its set to be a slave zone.

[rblakenyc]

Ah! The too small thought makes sense. It is a pretty big room and bathroom but doesn't have its own return. A contractor offered to add a return but its not really a comfort problem - was just pointed out by home inspector and been bugging me since. Thank you!

[mark beiser]

I'm curious if it even has a zone control.
The thermostat for the bonus room may only open and close a damper for the duct(s) to the room.

Screwy way to do it, but it sometimes gets done that way because it is cheap.

[mark beiser]

double post due to screwy forum software...