Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

How low can I set the pressuretrol?

michael_15 Member Posts: 231
I have one of those Honeywell subtractive pressuretrols with my 1-pipe steam system. (It looks exactly like the picture on pg. 124 of the "We Got Steam Heat!" book).

I have the main set to somewhere below 2 (2 is the lowest marked value) -- probably around 1.5. The Diff is set to halfway between 2 and the bottom, so I assume that's 1.

Now, correct me if I'm wrong, but once my thermostat starts calling for heat, the boiler will burn gas until the pressure hits 1.5. Then, regardless of the thermostat, it'll stop burning gas until the pressure drops to 0.5. Then, if the thermostat is still calling for heat, it'll burn gas again to 1.5. And so on.

Question: What/where here do I time the "boiler cycle"?

In any case, if I watch the boiler and feel my radiators, all of the radiators appear to get hot all the way through while the PSI indicator on my boiler is still at, well, zero. Once all the radiators are hot, the PSI slowly rises to. . . 2.5! before that little mercury tube tilts over and the boiler shuts off.

I assume this means that either the pressuretrol is miscalibrated or the PSI meter is miscalibrated. Regardless, since all my radiators get hot all the way across, should I continue to turn the pressure down without any lower limit (other than zero, of course)?




  • jeff_51
    jeff_51 Member Posts: 545
    don,t like honeywll either

    sounds like you are running pretty good, but it sure doesn,t hurt to keep playing with it. As you have prolly figured out, it doesn,t take much to heat a steam system as far as pressure goes. As Dan always says, high pressure goes to low pressure. On at .5 and off at 2 which should give you enough residual pressure to push back the condensate into the boiler. If you are maxing out at 2.5 on the high end, you are pretty close. I love trying to "guess" at the real pressure on a 30# guage. How about a nice big 5#
This discussion has been closed.