Common 24v C wire

Bill14174

Hello, I’m swapping out my old White-Rodgers series 80 thermostat for an Emerson Sensi Smart ‘stat. My old W-R ‘Stat did not have a common C wire; just red & white wires. There is an unused blue wire. Looking at my Honeywell RA832A, I see the red wire connected to the upper “T” terminal & the white wire connected to the lower “T” terminal. The blue wire was clipped off. Is there a terminal on my RA832A I can connect the unused blue wire as a common 24v C wire so I can wire up my Sensi Smart ‘stat?  I’d like to avoid using an additional 24v C Wire Adapter as a work around. 

HVACNUT

Nope. You can use the adapter or change the relay to a Taco SR501 or equivalent the offers a 24v R-C terminal block.

Alan (California Radiant) Forbes

Unfortunately, they don't give you a "C" terminal.



I'd switch it out for a Taco SR501.

Bill14174

Thanks for the tips on Taco SR501!  If/when my RA832A fails I’ll swap it out. Until then I’ll stick with my 24v C wire adapter work around.  

CharlesPrettyman

@Bill14174 - I need to do pretty much the same thing (a nest thermostat, but also the RA832A. In my case, however, there are two thermostats. Do you have any advice/recommendations from your experience?

Alan (California Radiant) Forbes

@CharlesPrettyman: Sorry to butt in, but there's a solution for that.

https://www.supplyhouse.com/Taco-SR502-4-2-Zone-Switching-Relay

james_bui

@Bill14174
doing the same thing. Do you have any picture of the wiring c wire adapter to the Honeywell ra832a? Thank you in advance.

HomerJSmith

You can use a auxiliary transformer and an isolation relay, too which is what a Taco switching relay would do. A simple fan control with a transformer and relay would do. The relay would not have to be a 2 pole relay.https://www.supplyhouse.com/Packard-FC90113-Fan-Control-Center-120-VAC-Primary-24-VAC-Secondary-SPDT-Relay?_br_psugg_q=fan+control+relay

chentong

I connect a wire to the transform as C wire. It work fine for my nest thermostat

Alan (California Radiant) Forbes

chentong said:

I connect a wire to the transform as C wire. It work fine for my nest thermostat

I wish they all could be so simple.