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Can't stop the heat

Last night my thermostat lost control of the boiler. The heat just kept coming until I turned of the service switch.
The oil company came today and replaced the device on the front of the boiler(the one with the red button). This is the second time this happened in a month so they also replaced my thermostat thinking it may be the problem. I had a rite-temp digital on there and they changed me over to a Honeywell YO YO. I have a couple of questions: I have one pipe steam heat.
1) The YO YO does not engage the heat until 2 deg below set temp and then runs until 3 deg above set temp? Isn't that temp swing a bit much? It puts a lot of pressure on my system. Can I adjust it?
2) Shouldnt my pressertrol be cutting the boiler out? It is set at .5/1.5 as you all reccomend. My valve stems will start leaking steam and the boiler keeps running. The old thermostst was more sensitive (kicked on at set temp and ran 2 deg over. I never had a problem with steam leaking. All the vents are new Gorton#2's on the mains, vari vents on the rads. Everything had been perfect.

Any help would be appreciated, also wondering if there is a particular thermostat you guys like for steam heat systems. I don't really care about set backs I just want what will work best.


  • BillW@honeywell
    BillW@honeywell Member Posts: 1,099
    Your service guy...

    should have set up the heat anticipator to match the current draw of the oil primary. If he didn't, call him back to do it. The T87 is an electromechanical thermostat, and swings of 2 degrees is about the limit of what that technology can deliver. I would suggest that you get a T8002C1000, a battery powered,+- 1 degree accurate, mid priced, mercury free programmable stat that can be set for 1 cycle per hour for steam.
  • Fred Harwood
    Fred Harwood Member Posts: 261

    The T87F (the F stands for fantastic) does the job simply and well, and permits anticipation that virtually eliminates large temperature swings.

    Your Pressuretrol should be set for no more than 2 psi. A Vaporstat (more expensive) really does the job.
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