connecting smart thermostat to RA89A pump relay
I want to replace three thermostats on a boiler with ra89a pump relays for each zone. The thermostats have only two wires so I want to install the thermostats by the boiler and just place wireless sensors in each zone. R and W get connected to T and T on the pump relay. Where does the C wire connect to? The pump relay has its own transformer that I should be able to utilize to power the thermostat so this should work right?
Comments
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IMO you are trying to directly marry two incompatible pieces of equipment. You probably need to add a power source (transformer) for the thermostats and a SPST relay for each RA89A relay between the thermostats and the RA89A relays.
I can't find any specifications on the transformer in the RA89A relay, so I believe the transformer is sized only to have the load of the coil of its relay, which it why the RA89A has no 'C' terminal.
Possibly you could replace the RA89A relays with a more appropriate switching relay device, that has a 'C' terminal. Not sure which method would be more cost effective.
Using powered switching relays with a 'C' terminal would be less confusing to wire.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Why not get a taco 4 zone controller and run the right wires? The control has C terminals, and you can add another transformer if needed.
Is there a reason why you need 3 wifi stats? I have 6 zones in my house, never touch the stats, set and forget.
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Thats a good idea thank you
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Yes that sounds correct one appropriate sized transformer could run multiple smart thermostats and buffer / isolation / switching relays.
However a Taco SR503 or a SR504 may be more practical solution and retire or repurpose the RA89A relays elsewhere.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
Three SR501 switching relays would work also. They do have a 'C' terminal, but I can't find a specification on the transformer size.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
3 rib relays and 1 transformer . about $100
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What brings on the burner when there is a call for heat?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Just to clarify. The 4 zone switching relay transformer should be able to handle 4 ecobee with no issue?
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The pump relays connect to an aquastat relay
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How? this diagram of the RA89A does not have a way to do that.
Unless you have a different relay with a cover from a RA89A (that cover fits many other relays like that) like a RA832A There are not X X terminals or other switching terminals on a RA89A to operate the boiler.
What does the inside of your control look like?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I guess I was mistaken with the model number because the pump relays have X X terminals
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You may need the second transformer.
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