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Simple Steam Heat Thermostat Recommendations

MikeC_3
MikeC_3 Member Posts: 15
in Thermostats and Controls

Hello -

I don't mean to be a nuisance and ask a question that seems to have been asked multiple times and answered ad nauseam but here I go.

The boiler at my mother's house was found to have developed a crack prior to this year's heating season. The boiler was replaced with a similar Weil-McLain unit. At the same time, it was deemed that the thermostat was faulty, and the 15+ year old Honeywell simple programable one was swapped for a LUX model # PSP511LC.

I had not spent enough time over there to assess how everything was functioning, but today with the frigid conditions in NY, I was able to and realized that without any doubt that it was short cycling.

It is a simple one pipe steam heat two-wire setup in a three story 3 story victorian house built circa 1900.

I have read that the gold standard as far as thermostats are concerned for this system is the older mercury Honeywell T87. I do not have that specific model but I do I have a Honeywell mercury T822 that I removed in good working order from my own hot water system and replaced with a Nest smart thermostat.

I plan to replace the LUX with this thermostat to see if that fixes the short cycling issue. On the newer version of this model, I see that the anticipator should be set at 1.2 for steam heat. However, the highest point on the dial is .9 (picture attached). It does move one position over to an unlabeled slot that I assume is 1.2 If I am incorrect, is .9 a poor trade off?

If this swap does fix the issue, I would prefer to leave things as it is. However, it is an unlikely scenario where I can convince my mother that function trumps aesthetic.

What simple non-mercury readily available thermostat would therefore be recommended?

If I decided to go with a simple programmable thermostat like the one that was replaced by the LUX, what would that be?

And finally, is there a functional two wire smart thermostat available that would allow me to monitor what is happening from afar? It isn't feasible to run an external transformer to power it.

Thanks in advance -

Mike

PXL_20250123_001938521.jpg

Comments

  • RTW
    RTW Member Posts: 170

    I too have single pipe steam system and was able to get a mercury Honeywell T87 just before mercury was banned years ago. It has performed flawlessly for a few decades - set it and forget it for the most part. Its possible these thermostats can still be had on Ebay etc.

    All the Best,

    RTW

    delcrossvMikeC_3
  • delcrossv
    delcrossv Member Posts: 1,663
    edited 1:01AM

    Got a mercury T87 off the bay for one of the apartments. Look there. For your stat, try it at .7 to start. You want a long anticipation with steam.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
  • MikeC_3
    MikeC_3 Member Posts: 15
    https://forum.heatinghelp.com/discussion/comment/1837203#Comment_1837203

    Ok thanks, I'll set it at the max and go for there?

  • delcrossv
    delcrossv Member Posts: 1,663
    https://forum.heatinghelp.com/discussion/comment/1837207#Comment_1837207

    Try a little less than max first and see how it works.

    Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.
    MikeC_3
  • MikeC_3
    MikeC_3 Member Posts: 15

    Got it.

    I did look up the old Honeywell digital (RTH7500) stat and it allowed you to set the maximum number of cycles per hour which I believe was probably "one". That worked fine for over a decade. I am not sure why the installers believed it was faulty.

    The new LUX has a swing setting that doesn't allow you to choose the number of cycles but gives you a range of 1 to 9 — more to less frequent.

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