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I have a single stage gas furnace in our wood shop that heats the main area and a storage / tools area. The furnace is connected to two nest thermostats and a honeywell HZ322 zone control unit. I want to add a 24v AC relay to the zone control to turn on a circulation fan at the far end of the shop when the zone calls for Stage 2 heat. I know W2 is the signal for stage 2 heat but where on the zone control should I wire the relay? Where do I get the + & - power to open the relay when stage 2 is requested.

The thermostat in that area is already wired for W2 / stage 2 heat to the control board. I can see the request for stage 2 heat come in but I just need to know where to wire in the relay? Do I wire it between the thermostat and control? OR do I tap off the furnace wiring side?
 

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You run a low voltage wire to where the power is for the circulation fan. Usually next to the fan in a 4x4 elec box. There should be your power for fan wired to that box also. ( power romex, fan (load) wire and a stat wire(18/2) in thd 4x4. Now add a SPDT RIB( relay in a box). Connect R to W2 (2nd stage heat)off the board and W to C.( common off the board ) At the 4x4 box you will connect the W and R to the coil of the rib, ( says what they are , most are 120 or 24v designated by color code) RIB has 2 switches labeled (common, NO, NC ) each switch us color coded so you know which wires go to what switch on the rib. Connect 120vac (Blk)to one of the switch commons. Connect neutral (wht ) from the power side to the other common. Now find which colors are NO (normally open) and connect the fan blk to the NO switch leg for the 120 blk . Neutral from fan (wht) to the other NO switch. When the rob is energized it will close the switch sending power to your fan
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