My 2nd floor radiant heat developed an irreparable leak, so I installed a hydronic coil on my Spacepak air handler. The thermostat will turn on the water pump, but not the fan. I switched the thermostat to cooling, and the AC works fine, so I know the fan works. Now, how do I get the thermostat to turn on both the water pump and the fan for the heating? My water pump has white connected to W, and red connected to RH. My AC has blue connected to Y, green connected to G, and red connected to RC. Will a jumper from RC to RH turn on the fan for heat? Also, my t-stat is an Aprilaire 8363.

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    It would help if you provided some photos of the wiring, and the make and model of all the equipment involved. – Tester101 Jan 18 '17 at 11:34

You need the wiring that turns on the pump to also turn on the fan. You may need to add a relay to isolate the fan from the pump due to different voltages or any other problem that could create. You could also use a temperature controller to run the fan which is how commercial installations do it. A controller like the " honeywell T675A1425" or a " White Rodgers 3F01-111 could be used, They would turn the fan on and off when hot water is present.

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  • The temperature controller (thermal switch) method is preferable - otherwise you blow cold air every time the pump starts. With a thermal switch, the fan comes on once the coil is hot, and shuts off after the coil cools down. – Ecnerwal Dec 18 '17 at 3:23

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