Wiring Fan Coil

How should I wire a relay (or should I use a relay) to turn on the fan on my fan coil.

I have a two speed heat pump so I cannot use any of the fan coil controllers I have seen.

My thought is to wire the E heat off of the honeywell 8100 series stat I use on the HP system which would allow me to turn on the fan at heat CFM and energize the zone/pump. I have two air handlers so I need either one to be able to energize the pump. With this I would also still be able to use the same stat to control HP functions (although not at the same time).

I think I should use something to isolate things but I am not sure what.

Is this set up a good idea and if so any thoughts on how?

Your Honeywell should do fine, as you say, using the Emergency Heat.

Some other t'stats will do this w/ Aux. instead of Emergency.

I am doing the same as you describe w/ 2 speed HP as-well.

I disconnected the "Toaster Elements" from the their relay(EH) and use that relay to "call for heat" from my coal heat source. Takes care of "isolation" of different voltage sources too.

One t'stat...w/ simple change-over...HP or Coal

recruiterman wrote:I think I should use something to isolate things but I am not sure what.

I use an aquastat on the fancoil pipe to start the fan on the heat pump, with a second thermostat to start the circulator on the coal stoker. Their are no wires that tie the coal to the heat pump,only heat in the pipe starts the fan, and this way I can keep both thermostats on, just keep the heat pump thermostat set lower, in case one would fail, their is a back up heat.