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Pressuretrol reading 14 psi on residential steam boiler. Sight glass completely filled with water. Lwco fills boiler with sight glass showing completely full. Lwco indicator shuts off properly, power light on. Unimatch properly turns off in conjunction  with lwco. Why is pressure so high? Set for0.5 with 1.5 differential. I know sightglass valves are probably full of sediment. Why is pressuretrol at 14 psi? What am I missing?


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,840
    Do you mean Pressure Gauge when you are saying PRESSURETROL? Pressure-trol is a control near the gauge that has the pressure settings you mentioned.

    The reason the system is off is the pressure is too high. the reason the pressure is too high may be a result of water well above the top of the sight glass. Like, maybe 32 feet above the gauge glass. (2.31ft x 14PSI)

    Drain the water out until the water level is below the top of the sight glass. when you get closer to that the burner will magically start.

    You will need to find out why the water got in there in the first place
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    You mean, I presume, the pressure gauge reads 14 psi? The boiler -- and probably a good portion of the piping if not all of it -- may be full of water.

    Shut off the boiler with the emergency switch -- that's step one. Also shut off the water feed to the boiler (not with the automatic, but with the valve). If there is a tankless hot water heater, shut off the water to that, too.

    Then start draining it. If it's that full, you are going to have a lot of water to drain -- I hope there is a handy floor drain.

    One of two things will happen. At some point the sight glass will show a water level, rather than being clearly full of water. Or, you will empty the boiler completely. If the first thing happens, you have at least gotten to the point where, if it's cold out, you are on your way to restarting the boiler (you're not there yet). If the second thing happens, then indeed the sight glass is not showing the water level, and it will need to be cleaned up, including the ports into the boiler. This is not for the faint of heart. You will need, at least, new gaskets for it, and it's best to have a new glass tube on hand as they are very fragile. Do not even think of restarting the boiler until you are sure that the sight glass reliably reads the water level.

    Now we have a boiler for which we can presume we have the right amount of water in. The next question is -- where did the extra water come from? I you have a tankless heater, try that first -- reopen the valve to it. Nothing should happen. However, if it is leaking, the water level in the boiler will rise -- and that is at least part of your problem. You will need to figure what to do about hot water -- replace the coil (may be easier said than done) or abandon it and come up with a different way to heat the domestic water.

    If you don't have a tankless coil, or if it passes the test above, open the valve to the automatic feeder. Again, with power off, nothing should happen. If the water level starts to rise, the automatic feeder is misbehaving. Some can be repaired. It may be easier, and better, if it's older to simply replace it.

    Now, making sure that the thermostat is NOT calling for heat, turn the power back on. Nothing should happen. If the feeder starts feeding, there is a problem either with the low water cut off (there are separate circuits for the burner and the feeder) or with the feeder. This needs professional service.

    Then take the pigtail and pressuretrol off and make sure that the pigtail is clear. (I'm assuming, by the way, that the boiler was not firing at that high a pressure -- if it was, don't even think of turning it back on until you find out why the pressuretrol didn't cut it off -- which could be a the pressuretrol not sensing the pressure -- or the burner failing to shut down on the safeties; that's happened and is very dangerous).

    You're not done. If the pressure really got that high (the pressure gauge, by the way, should be reading zero or close to it at this point), you need to consider every single vent on the system and, if there are thermostatic traps, the traps. None of them are built to take that pressure, and they may be stuck closed, stuck open, or simply destroyed.

    If you -- or a professional -- are satisfied that there is the correct water level in the boiler, and that the safeties will actually turn off the burner, then you can, paying very close attention, try restarting the boiler. Keep a very close eye on the water level and the pressure -- do not leave the boiler running unattended. if the water level holds, and the pressure doesn't rise quickly, you may be in luck. Have someone else start checking radiation to see if it is actually heating up as it should, and, where and if it isn't, contemplate damaged vents or traps. If the pressure rises fairly rapidly, your main vents are probably jammed closed. A sharp whack may release them. Then again, it may not. If the pressuretrol doesn't shut off the boiler at its setting, turn the boiler off manually and go back to square one.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,061
    edited December 2020
    In addition to all said above:

    Being a weekend, you may not want to remove the sight glass.
    If you think you got the water drained below the sight glass, you could close the lower valve below the glass, and then remove the small plug directly below the glass. Maybe spray it with WD first
    and use a good wrench. That plug is brass so carefully unscrew.
    The glass should drain down thru that port.

    Then you can partially open the valve, unscrew the bonnet under the handle and remove the valve guts. Using one of the glass guard rods you can prod into the boiler to open that port.
    Do the same for the top valve.
    As you refill you would flush out the lower valve port.

    With the water level correct you then could close the lower valve and open the drain port and witness that the glass water level drops.

    Close the drain port and open the lower valve and witness that the water level returns.

    This will clear the glass ports without removing the glass and risking breakage.

  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,007
    Have any of you considered the possibility the temperature somewhere in the system is above 212?

    Not knowing the piping arrangement, I can't judge if some "hot" water can flash to steam.

    Hopefully he has shut off the heat source and the system is cooling down.