Tstat wiring - dual transformer, 1 "R" connection

[John]

I have a dual transformer system - one for heat, one for cool. The thermostat I'm replacing has an Rc and an Rh connection. The new thermostat has a single R connection. The transformers are in phase with each other, however, the heat one puts out 24vac, while the cooling one is at 26.7vac. Can I connect them both to the R connector on the new thermostat, or will that not work?

Thanks

John

[Carolina Breeze HVAC]

Wrong thermostat sub-base. It will not work, altho, you COULD make it work as you have now, with more re-wiring that is needed.

Get a thermostat with the proper sub-base. Honeywell for example is including the RC and RH terminals on almost every one they offer in the new Vision line, with a jumper that you remove to allow for the sep systems to work properly. Robershaw also does this, and depending on the needs and wants of you, in what you want out of your stat, Robertshaw may be the way to go....its cheaper, altho normally you cant buy them over the counter.

[John]

Thanks for the information.

Here's what I'm trying to do: I'm replacing a White-Rodgers thermostat with a wireless one from Carrier. We recently had AC retrofitted to our house. The house is a small two story cape, and because of the size and space constraints, the AC is a single zone. The thermostat is on the ground floor, and my wife, who is handicapped, would like to be able to adjust the temperature while upstairs. It's very difficult for her to make the trip down the stairs too many times.

If need to re-wire, I will - what would have to be down? Is it a matter of installing a single transformer with enough power to run both circuits? Alternatively, do you know of a different wireless system or other setup that would fit our needs.

Thanks again.

John

[Bud]

If wired right using a single R base should work. It is actually a code violation since you are combining 2 limited power sources which could produce a source that exceeds the maximum. (Because it is a limited power source you can use small thermostat cable instead of #14 Romex, for example. The whole system could probably be wired to run off of one transformer. Or the heating side could be connected to the sub-base and relay could be used to separate the cooling side; this is pretty easy to do.

Bud--