Boiler Shutting off too soon

Martin Gritsch

We have one-pipe steam heat in our 1926 house and have had no problems worth mentioning since we bought the house eight years ago. Lately, though, the boiler (40+ years old) has been shutting off before it reaches the set temperature on the thermostat. When I increase the cut-out on the pressuretrol, it works fine again, but a few days later, the problem reappears. (Plus if there is one thing I learned from Dan’s books, it is to keep the pressure down.) Does this sound like a new pressuretrol would help? Or do you think that after eight years of virtually no problems, all of a sudden another problem popped up (e.g., air not venting sufficiently)? Thanks in advance!

John@Reliable_14

Blocked pig tail could...................

cause this. Anything else change? new thermostat, lamp or tv, computer, etc. moved closer to thermostat, if not back to pigtail/pressuretrol.

David Efflandt_2

Could be something else

When I discovered "The Wall" after buying a home without knowing anything about steam (1-pipe), I discovered that my pressuretrol was set way too high (on 1 yr old boiler). When I adjusted it down to where it should be (as low as it goes) I discovered why. Apparently the vent damper on my gas boiler would stick shut when hot. So the first time it cycled off from steam pressure, the vent damper would close and not reopen (or refire) until it cooled. So I temporarily locked the vent damper open until I could get it replaced.

Of course various other things can get gunked or plugged up over the years if they are not serviced (plugged pressuretrol pigtail, plugged vents, etc.)