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White Rodgers Thermostat 90 series 1F97-371 with a Relay

Hi, again first I want to thank you for a speedy answer to my thermostat problem. As I said before I have a steam system of course there is no circulatory motors with the system,but there is a Fan Relay with N.O. and N.C. contacts that is mounted near the 24v Transformer. The High Limit Switch is the load in witch the Thermostat completes the the thermostat circuit. Does this Relay need to be wired into the circuit for just (Heat only)? If so how do I do this? I'm attaching the print of the White Rodgers Type 8A04-1 Fan Relay. I'm looking at this print but I don't see any reason to have to use the relay, but please correct me if I'm wrong. Thanks again Carol. Kevin


  • Kevin it may be

    that the relay is packaged with all the boilers from this manufacturer. You are correct the relay which is a spdt relay designed to bring in a circulator or in the case of a forced warm air system the fan for heat or cooling. Typically a relay is not needed for steam. They may have included it to eliminate problems with programmable thermostat interference. Do you have an automatic water feeder, if so it may be used to run the feeder?

    A question for you, is it working now to give you heat? If it is leave it alone.The old adage if it ain't broken don't fix it.

    Another question what is the boiler make and model? Do you perhaps have a wiring diagram for the boiler? If so post it as it will help to answer your questions.

    Is this thermostat a two stage thermostat? In looking at your other post you said you have two gas valves. A two stage will have a W1 and W2 terminals. In looking at diagrams for your thermostat it does not have two stage terminals.
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