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[Kccondo]

I install a duct booster fan for my forced air furnace. I want to plug it into an x10 appliance module. I bought a um506 low voltage switch that I want to wire to my 24 volt thermostat.  I want it to turn on the fan when the furnace blower fan starts (both for heat and air) and turn off when the fan stops.  The thermostat has 4 wires: W-Heat call control, Y-cool call control, RH-power for heat and cool, and G-fan. I want to know what wires do I connect from the thermostat to the front of the um506 control switch?  Also, do I disconnect the wire from the thermostat and connect them to the um506? Or do I run additional wires from the connections to the um506? Please help, thanks

[dave w]

I install a duct booster fan for my forced air furnace. I want to plug it into an x10 appliance module. I bought a um506 low voltage switch that I want to wire to my 24 volt thermostat.  I want it to turn on the fan when the furnace blower fan starts (both for heat and air) and turn off when the fan stops.  The thermostat has 4 wires: W-Heat call control, Y-cool call control, RH-power for heat and cool, and G-fan. I want to know what wires do I connect from the thermostat to the front of the um506 control switch?  Also, do I disconnect the wire from the thermostat and connect them to the um506? Or do I run additional wires from the connections to the um506? Please help, thanks

The UM506, Universal Module will not do what you want. You need X10 PF284 or PSC01 Powerflash Interface instead.

The UM506 will provide a relay closure across the screw contacts when it receives an ON command and opens contacts with an OFF command. So all it will do is short your thermostat.

The PowerFlash will send an ON command ( to your duct boost Appliance Module) when you provide a closure. But connecting it between the RH and G terminals of the thermostat will not do the job. It will either see 24VAC or a closure all the time so would never send the OFF signal. The proper way to do this is to find the fan relay in your air handler and use the relay coil voltage to feed the Power Flash. The 24VAC is too high for the PowerFlash so you need a diode (Powerflash recognizes AC or DC) or resistor to reduce the 24V.

Based on you wiring question, you might want to get an HVAC person involved.

[Kccondo]

Thx, so how would I wire the x10 pf284 to the thermostat as stated in my first post? What wires would I connect to the front of the Unit?

[dave w]

Thx, so how would I wire the x10 pf284 to the thermostat as stated in my first post? What wires would I connect to the front of the Unit?

The thermostat does not have "Common" and you need "FAN and "Common". You would need to wire from Fan (G termainal) to "Common" which is the same as the fan relay coil. To make this clearer, you can't do it at the thermostat.