Dual Zone Furnace

[Joe Arcaro]

A furnace with two t-stats (one for the main level, and one for the lower level).

When the t-stat is turned up for the main level the furnace operates. When the t-stat is turned up for the lower level the furnace does not kick on.

What can be some of the reasons be for this?

Thanks,
Joe

[Mark Reinmiller]

I am assuming that this is a zoned system. Did you see zone dampers? If so it could be a problem with the zone controls or the T-stat.

I sometimes see systems with a thermostat on the first and second floor, but it is not a zoned system. With this setup the second floor T-stat controls AC and the first control heat.

[Lon Henderson]

Recently, I was in a house with two thermostats, but one didn't do anything. After a little investigation, I realized that one wasn't wired to the furnace. Apparently the owners would rather have a dead thermostat on the wall than repair a hole in the wall.

If the furnace isn't zoned, then you may have a similar situation.