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Steam Boiler Pressure & Some Of My Adventures

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Comments

  • mattmia2
    mattmia2 Member Posts: 14,635

    my bet is some sort of mechanical force on the gauge as the boiler heats is flexing the bourdon tube and rack in the built in gauge.

  • cobyschaef
    cobyschaef Member Posts: 19

    Alright, so, disconnected one of the pressuretrol wires, and it does not fire when there's a call for heat. So I took the whole thing off and it's not clogged, even the threads into the boiler are clean. I was able to pressure test it just by blowing into the pigtail. The 15psi gauge I have installed seemed to be reading correctly. I heard the pressuretrol click when I got to around 1.5psi and when I stopped blowing and the pressure dropped it reset.

    Based on that I guess the other gauge would then be bad and perhaps it wasn't operating at 10 psi yesterday?

  • Steamhead
    Steamhead Member Posts: 18,062
    https://forum.heatinghelp.com/discussion/comment/1867980#Comment_1867980

    Yup. Unless that gauge is on a pigtail, and that pigtail is plugged.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • 109A_5
    109A_5 Member Posts: 3,082

    Ok, just so I am clear as to what you did. You removed the new Pressuretrol, the new 15 PSI gauge and the pigtail as one whole assembly and blew into it like the boiler pressure would go into the assembly and it all seemed to work OK, correct? The tapping into the boiler casting is also clear, not blocked. If all that is true, it certainly sounds like the 30 PSI gauge is giving you erroneous reading, I'd replace 30 PSI gauge.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    cobyschaef
  • cobyschaef
    cobyschaef Member Posts: 19
    edited October 15
    https://forum.heatinghelp.com/discussion/comment/1867986#Comment_1867986

    It's not on a pigtail. It's an internal syphon. I ordered a replacement because I think it's just not working. I think I got to the bottom of it. I let everything run long enough so that all my radiators got hot. It looks like I may have a few vents that are no longer working properly, and I may have to increase the venting rate to balance things out a bit. I tested the pressuretrol while the boiler was running. If I bottom out the cut out pressure, it stopped the boiler from firing, and resumed if I increased it to 1.5psi again. So looks like that's working properly. I'm assuming that two things are happening.

    1. My LWCO runs an intermittent test every 10 minutes. I'm guessing this is allowing for enough of a pressure drop that the pressuretrol is rarely kicking in.

    2. The vents that I have that are not closing properly are probably allowing enough of a pressure drop so that the pressuretrol also is not kicking on. By the time I finished running everything, 3 of my radiator vents had not closed yet, but two definitely should have. The 3rd is also pretty old and I probably need to replace it anyway so that it vents more quickly.

    So after doing all the replacements that I have, everything seems to be running pretty well. Fairly minimal water line movement, absolutely no water hammer at all, no leaking valves or radiators. Just a bit more work to do to balance the radiators.

    bburd
  • mattmia2
    mattmia2 Member Posts: 14,635
    edited October 15

    if the boiler matches the connected edr it shouldn't build detectable pressure or at least not until after very long cycles. you could replace the cyclegard with a safgard.

  • Steamhead
    Steamhead Member Posts: 18,062
    https://forum.heatinghelp.com/discussion/comment/1867992#Comment_1867992

    If that were mine I'd use a standard gauge and pigtail. You can clean a standard pigtail, but not an internal syphon.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    109A_5
  • cobyschaef
    cobyschaef Member Posts: 19
    https://forum.heatinghelp.com/discussion/comment/1868012#Comment_1868012

    Could I use an internal syphon gauge with a pigtail? I still have the old pressuretrol pigtail and it's pretty clean. The replacement gauge is also an internal syphon. If I don't need to return it to get a different one, then all the better.

  • Steamhead
    Steamhead Member Posts: 18,062
    https://forum.heatinghelp.com/discussion/comment/1868030#Comment_1868030

    Never tried that, but I don't see why it wouldn't work.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • 109A_5
    109A_5 Member Posts: 3,082
    edited October 16

    Sure, if you pre-fill the pigtail the gauge's internal syphon may never get any junk in it.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 3,082
    edited October 16

    I wonder if the old 30 PSI gauge has a plugged internal syphon so when the boiler heats it up and the internal air (in the Bourdon tube) expands and gives the erroneous reading.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Steamhead
    Steamhead Member Posts: 18,062

    Could be………….

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • mattmia2
    mattmia2 Member Posts: 14,635

    i could see it with water, with air it is a lot less likely

    if you tweak the case it will bend the bourdon tube and move the needle so i think the jacket or something is pushing on it

  • 109A_5
    109A_5 Member Posts: 3,082

    Although hard to see in the pictures the boiler jacket does not seem to contact the back of the gauge. The expansion coefficient of air is greater than water, assuming any trapped water does not boil.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • mattmia2
    mattmia2 Member Posts: 14,635

    but air is compressible. water is not. air will simply compress when it gets hotter and the pressure change over 100 f degrees will be very small. water can not compress so it has to expand the bourdon tube as it expands

  • 109A_5
    109A_5 Member Posts: 3,082

    I kind of doubt the Bourdon tube is full of water, although probably not impossible. And the Bourdon tube is made to expand when the pressure goes up, so when the possibly trapped air expands (and compressed, vessel volume is mostly consistent) due to the boiler's heat the gauge erroneously goes up. There simply could be a mechanical defect too.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • BobC
    BobC Member Posts: 5,531

    I'd bet there is a blob of crud just i9nside the theded inlet the pigtal threads into the boiler casting.Even if the wiring were wrong the new gusge would read assunint it's on the same tapping the p-trol is.

    If you take the cover off the p-trol you will see a metal bracket the goes between the switch should sense the pressure and a fixed point. With tho boiler off you can get a screwdriver blade under that lever and hear the swutch click as you move yhe blade up and down up and down. If you do this whikle the boiler is running it should shut the boiler of till you remove the pressure on that lever.

    Bob

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • cobyschaef
    cobyschaef Member Posts: 19
    https://forum.heatinghelp.com/discussion/comment/1868061#Comment_1868061

    I cleaned everything, including the threads inside the boiler casting. I tested the pressuretrol while the boiler was running and it shuts it off like it's supposed to. I just don't think I'm actually getting enough pressure currently for the pressuretrol to need to turn it off. But that's only after testing it out a few times, it may be different in the dead of winter. Also the new gauge I put on isn't a super lower pressure gauge, so I'm guessing the amount of pressure is just not enough for the gauge to detect.

  • mattmia2
    mattmia2 Member Posts: 14,635

    the pressure should be in the order of a couple inches water wc if the boiler matches the system it connects to.

  • mattmia2
    mattmia2 Member Posts: 14,635
    https://forum.heatinghelp.com/discussion/comment/1868048#Comment_1868048

    you're going to make me do the math on this again…i think i did it in a thread a couple years ago.

  • 109A_5
    109A_5 Member Posts: 3,082

    You could build a Manometer out of clear tubing and connect it to the boiler. Or a gauge that connects to the boiler drain valve for more opinions.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • 109A_5
    109A_5 Member Posts: 3,082
    https://forum.heatinghelp.com/discussion/comment/1868087#Comment_1868087

    Don't bother I found a Gay-Lussac's Law Calculator and convinced myself that it is probably mostly full of trapped water. Or a mechanical issue, I've seen other gauges suffer the same erroneous readings fate. Never had the opportunity to do a Postmortem.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    mattmia2
  • mattmia2
    mattmia2 Member Posts: 14,635

    If you have ever accidentally pushed on the case of a bourdon tube type gauge while working on something near it, you will notice the needle moves and it throws it out of calibration. I suppose there are versions with heavier cases that are secured with more screws that don't have that problem.

  • cobyschaef
    cobyschaef Member Posts: 19

    @mattmia2 @109A_5 Tell you what, you're both invited over and we can take it apart and see who's right 🤣

    Grallert
  • cobyschaef
    cobyschaef Member Posts: 19
    edited October 28

    Just an update, everything looks to be running great! Added a new 30 psi gauge and now both of my gauges are actually reading correct pressure. The pressuretrol is cutting off the boiler at the right pressure as well. The whole system is heating well, but as previously said, I need to do a little bit of balancing. I may end up moving my thermostat as well. Currently, it's in one of the two coldest room, but it is also at the end of the longest main and still has quite a bit of air to vent since the main vent is at the dry return of this main. Once my new radiator vents are in, I'll balance everything out and see if I end up needing to move the thermostat to the other room. Otherwise, everything is running way better than it ever has! The boiler has been off for several days, and after turning it on this morning, it took less than 15 minutes for it to make steam and start filling the radiators. My wife was even amazed at how silently it was running.

    Thanks to everyone who helped me out and this wonderful community!

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