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I need to replace the Zone 3 relay in my Taco SR504, but…

Customer Question
I need to replace...

I need to replace the Zone 3 relay in my Taco SR504, but there are five 28 volt relays and they are not numbered on the board -- or in Taco's documentation.

Contractor's Assistant: I'll do all I can to help. How long have you been dealing with this?

A couple of days. I diagnosed the blown relay, so there is not a problem with the pump or power feed.

Contractor's Assistant: Do you plan on doing the work yourself?

Yes, I have a replacement relay.

Contractor's Assistant: Anything else we should know to help you best?

No -- I just need to know which relay matches Zone 3. There are six relays on the Taco SR504. The first on the left is a 120V relay. The second to sixth appear to be 28 volt relays, with no numbers.

Submitted: 10 months ago.Category: HVAC
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Answered in 1 minute by:
11/10/2017
HVAC Technician: Rick, HVAC Supervisor replied 10 months ago
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,829
Experience: 40+ yrs. experience as a licensed oil & gas technician.
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Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

It's the ice cube between the thermostat and pump leads on the relay board for that zone.

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Customer reply replied 10 months ago
Dear Rick: I wish it was that simple. I have the Taco wiring diagram for the SR504 and the wiring posts under the six relays are labeled -- but they do not correspond to the relays above, which are not labeled -- except for the 120V relay on the left side. This leaves five 24 volt relays to the right, for four zones. One of them is probably the 'priority' switch, if you enable that feature. So do you know how the five relays are numbered?
HVAC Technician: Rick, HVAC Supervisor replied 10 months ago

I've installed and serviced this product since it was introduced. Yes it is that simple. The relays to the left away from the zone wiring are not zone control relays.

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Customer reply replied 10 months ago
Dear Rick: The relays for the original Taco SR504 are in the middle of the PCB board, with wiring connectors above and below. So the relays are not "to the left". I attached a PDF of the original SR504 install guide for your review.
Thanks, ***** *****
HVAC Technician: Rick, HVAC Supervisor replied 10 months ago

I'll say this one more time. The 2 relays on the left are not zone control. Granted the zone control relays don't fall exactly between stat and circ wiring but the order right to left is the same.

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Customer reply replied 10 months ago
Dear Rick: Thanks for your quick reply. I wish Taco documented this basic fact about their controllers -- the documentation for the newer version still doesn't label the relays. So based on your knowledge, Relay 1 = 120v, Relay 2 = Priority, and Relays 3, 4, 5 and 6 = Zones 1, 2, 3 and 4. Attached is a JPG image of the controller layout. If this is correct, please let me know -- and I hope it will be helpful if another customer asks the same question.
Thanks, *****
HVAC Technician: Rick, HVAC Supervisor replied 10 months ago

You have the zone relays labeled correctly

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