HVAC relay question - AVS Forum
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rs691919's Avatar rs691919 08:30 PM 01-14-2013
Trying to figure out how to turn on my return fan when the thermostat turns on. The basement zone is on a damper system with the main zone upstairs - controlled by a zone panel. I have my Nest thermostat wired into the zone panel (with a C wire) and it works just fine. We got a 24V-110V relay and wired from the Common wire of the damper on the zone panel into the relay. When the thermostat turns on, the relay clicks but no power is transferred. Contractor believes he has the relay wired correctly. He tried just bare wire coming out of the relay but still gets nothing. Any thoughts as to what we're doing wrong and how to make it work?

J_P_A's Avatar J_P_A 06:15 AM 01-15-2013
Can you post a schematic of how you wired the relay? Where are you getting the 120 V for the fan from, and how is that wired into the relay and to the fan?
rs691919's Avatar rs691919 06:22 AM 01-15-2013
I'll have the contractor draw a schematic and post it as soon as I can, thanks!
rs691919's Avatar rs691919 09:02 AM 01-27-2013
Here's a diagram of the wiring that my contractor gave me. He says that the relay clicks when the thermostat turns on, but no power leaves the Honeywell relay:


Mr.Tim's Avatar Mr.Tim 10:51 AM 01-27-2013
Looks like on the line side the yellow should be tied to the black (if it isn't that way by default). Black on the load side connects to the rheostat.

Besides that, I believe you need the isolation relay as noted in the instructions. The R8239A has it's own power supply, as does the zone control panel that actuates the damper. You could try disconnecting the transformer on the relay and powering the R and C with the transformer from the zone control panel.

Frankly you would be better off with an ice cube relay with a 24v coil. The coil would be wired in parallel with the wires going to the damper motor. The contact would be a simple closure with 120v in and out.

What zone control panel do you have? Maybe there is another way to do this.

Tim
rs691919's Avatar rs691919 05:13 PM 01-27-2013
Quote:
Originally Posted by Mr.Tim View Post

Looks like on the line side the yellow should be tied to the black (if it isn't that way by default). Black on the load side connects to the rheostat.

Besides that, I believe you need the isolation relay as noted in the instructions. The R8239A has it's own power supply, as does the zone control panel that actuates the damper. You could try disconnecting the transformer on the relay and powering the R and C with the transformer from the zone control panel.

Frankly you would be better off with an ice cube relay with a 24v coil. The coil would be wired in parallel with the wires going to the damper motor. The contact would be a simple closure with 120v in and out.

What zone control panel do you have? Maybe there is another way to do this.

Tim

Thanks for the info, Tim! The zone panel controller is a Honeywell HZ311. I will pass on this info to the contractor, and see if he can make it work. I now my HVAC company can do it, but their cost will be significantly higher.
Mr.Tim's Avatar Mr.Tim 05:29 PM 01-27-2013
I looked at the HZ311 and you need the isolation relay (or power the R8239 from the zone controller). Or you could use an ice cube relay; the 70315K11 would be one solution. You just need to sum the current draw of the relay and of the damper to make sure it doesn't exceed the rating of the zone control panel.

Tim
rs691919's Avatar rs691919 05:44 PM 01-27-2013
I will look into the ice cube relay. Or rather, I will have Mike (contractor) look into it, as this is a bit over my head at present! But thanks nonetheless for the info and time, that gives us something to test out, as we were coming up empty with all our troubleshooting.
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