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Smart Thermostat With Steam Heat

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pufffee1
pufffee1 Member Posts: 3
Hi Everyone

I was hoping to get some advice. I have an older house with Steam Heat, 1 zone, with radiators. Its a two family but only 1 zone. I bought it 6 years ago and had a Smart Thermostat put in. The house was missing the C wire but the electrician used a doorbell Motor(I believe that is what it is ) and hooked everything up. It has worked great and then the Controller died, Oil company fixed, 2 years later it broke again, and then again today I woke up to a house that was 80 degrees. This time, the Tech said my thermostat is most likely 99% of the problem because smart thermostats are not good for Steam heat. Something about the time it takes to heat and other things I was not understanding unfortunately. He said you can get a non smart programmable Thermostat and he said he can almost guarantee the problem goes away. Does this make sense?

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
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    That is not the correct wiring configuration for that control. I will be happy to offer you a correct wiring diagram. Please stand by.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    edited February 2023
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    This is the proper wiring diagram for using a smart thermostat on your Weil McLain SGO boiler

    I have selected the diagram from the instruction manual and made changes to reflect the current changes made by your service provider. It includes the R7284 primary control. Since there is no Common Wire terminal on the R7284 control, you must use an isolation relay in order to power the Common terminal (C) on the thermostat with a separate doorbell transformer. The reason the primary controls keep failing is that the two different transformers (the Door bell transformer and the internal control transformer) are out of phase causing overheating. By isolating the two different transformers with a relay, the problem will be eliminated.

    Only the wires in the gray shaded area need to be addressed. Purchase this relay (or one similar) )to correct the problem. https://www.supplyhouse.com/Jard-92290-SPST-24V-General-Purpose-Switching-Relay. You may be able to get one locally at an appliance repair, HVAC or plumbing supply company.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • pufffee1
    pufffee1 Member Posts: 3
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    @EdTheHeaterMan This is great! Is an isolation relay also referred to as a Rib Relay? My friend is Master HVAC guy and I was trying to confirm what he is saying with people on this site and it appears your both most likely saying the same thing. This explains alot, but I wonder why it does not immediately kill the controller, does it just take time to continuously overheat and then finally die?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    edited February 2023
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    RIB is one of the companies that make the proper relay.

    When a transformer is out of phase, it can take hours before the electrical parts heat up enough to fail. Since your burner only operates for 15 to 20 minutes at a time, it can take a year or two for the failure to happen. Also, because the burner operates longer cycles the colder it gets outside, the failure will happen when you need the burner the most. When it is cold.

    RIB relay is overkill. it can do so much more, that is why we have them on out service trucks. Because it can do so many things, Your Isolation relay being one of them. If that is all that is readily available, and it saves labor of driving to the store to get one, then go for it. If your HVAC guy is going to the store to buy a RIB relay, then he could save money on a lower price relay like the one I showed you. Or this one. https://www.supplyhouse.com/Jard-92370-SPDT-24V-Heavy-Duty-Fan-Switching-Relay. but the RIB will also work https://www.supplyhouse.com/Functional-Devices-RIB2401B-Enclosed-Relay-20-Amp-SPDT-with-24-VAC-DC-120-VAC-Coil

    With the RIB relay, it is an easy DIY fix in you are up for it.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • pufffee1
    pufffee1 Member Posts: 3
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    Thanks! @EdTheHeaterMan I am going to see if my HVAC friend has the bandwidth to do this. It also looks like a DIY but I dont want to mess around with it. Especially when I just bought a new controller. This is great info and it is really nice to have resources like this site and people like you that are willing to help us less technical folks ; )
    EdTheHeaterMan