I am adding an hydronic heat coil to my heil high efficiency furnace. I'm installing a 24volt relay wich I already have. I need to know how to wire this up. The furnace is a 1995 model.
My objective is to run the fan on thermostat switch,and keep the LP heat for a back-up.
Thanks

Are you going to use two thermostats. One for the furnace and one for the hydronic heat? If so you will need to make sure and isolate the cooling speed of the blower motor so two speeds can't call at one time. Give us more info if you can.

I am using another thermostat, I assume the relay, wich has a 24v coil,must be energized from the 24v trnsformer. There are in/out terminals(two pins on the bottom of rely)
For this. The two center pins above I assume are for the thermostat, and the side terminals break into the fan circuit. So I need to use the correct wires to the fan,any other pitfalls I should look out for?

Most relays have a wiring schamatic on them, the coil terminals of the relay are where you would connect the 24 volts from your new thermostat controlling your hydronic heating and the "c" or common and the "no" normally open is where you can connect the "g" from your furnace thermostat and "R" to bring on the fan relay of the furnace. Hope this helps. Mike