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.

Pressuretrol cutting out too late?

jweob
jweob Member Posts: 14
edited November 2022 in Strictly Steam
I just cleaned out the pigtail on my boiler - it was totally jammed with sludge and the pressuretrol wasn’t doing anything.

After cleaning it out I added a new pressure gauge because the existing one was suspect. I then fired the boiler. My cut in is set at 0.5 and differential at 1 psi, so I expected a cut out at 1.5 psi. However the new pressure gauge was reading 3.4 psi when the pressuretrol cut out. Is it expected that it is so inaccurate? Is there a way of calibrating it? I am already at the minimum setting.


Comments

  • jweob
    jweob Member Posts: 14

    This is picture of pressuretrol with pressure gauge in background
  • 109A_5
    109A_5 Member Posts: 483
    Hello @jweob,

    Before I tried to calibrate my pressuretrol I would get a third opinion. It is probably the pressuretrol that is not correct but I would want to be sure.
    Testing the Accuracy of Honeywell Pressuretrol
    https://youtu.be/mE1-QuUx4_c
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • pecmsg
    pecmsg Member Posts: 3,567
    Trust the pressure gauge not the control gauge. 
    jweob
  • mattmia2
    mattmia2 Member Posts: 7,184
    With about 10 ft of tubing you could make a water manometer and get a second opinion.
    109A_5jweob
  • dabrakeman
    dabrakeman Member Posts: 325
    Advise offered to me from @Fred 7 years ago. Worked perfectly. On same settings got my 3.5psi cutout down to 2 psi (since have found ways to avoid ever reaching that cutout). As it says go in small increments. If go too far the boiler will not reliably cut in.

    From @Fred: Inside the Pressuretrol, right below the micro switch, there is a pivot arm. At the end of that arm you will see a screw pin that is activated by the diaphragm at the bottom of the Pressuretrol. If you look very carefully at that screw pin, you will see it actually has a tiny (I mean tiny) hex head on it. It takes a .050 hex wrench and you can turn it clockwise (Towards the bottom of the Pressuretrol to decrease the Cut-out pressure or counter clockwise to increase the cut-out pressure (which none of us want to do but who knows, your Pressuretrol may be really screwed up!). Turn the power to the unit off first. You may find the first attempt to turn that screw a little bit stubborn (relatively speaking) because it has some Locktite on it but it does turn. Don't turn too much, a fraction of a turn goes a long way towards getting it adjusted where you want it (maybe 1/32 inch turn to start with). You may need to play with it to get it exactly where you want cut out to be.


    mattmia2jweob
  • mattmia2
    mattmia2 Member Posts: 7,184
    edited October 2022
    You should probably put a drop of loctite or nail polish or glue on it after you are done since the loctite is likely the only thing keeping it from turning on its own with use.
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 809
    @mattmia2 Good comment, but

    3.4 psi x (1/(0.435psi/ft)* = 7.8 ft of water column or ~94 inches of water column.

    If the water line is 2 ft above grade, then the top of the water column would be almost 10 feet high. So, the question becomes how high of a pressure can be measured in a typical basement (assumed) 8 feet high?

    Back calculating 6 feet of water x 0.435 psi/ft of water is 2.6psi.

    1 foot of water column is about 0.435 psi is what I was taught many decades ago.

  • mattmia2
    mattmia2 Member Posts: 7,184
    My assumption was that you could work out which one was wrong before you built enough pressure to blow the water out of the tube. You are really only interested in if it is actually going above 1.5 psig or not.
  • BobC
    BobC Member Posts: 5,380
    If you use loctite be aware there are different grades that range from welded to mild. Use the milder strength so you don't round out the 0.05" hex set screw. Glyptal or a drop of nail polish are excellent choices as well.

    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
  • 109A_5
    109A_5 Member Posts: 483
    If @jweob really wants to know the actual cut in and cut out pressure of the original Pressuretrol calibration using the Manometer and the basement height is too low just extend the clear tubing part of the Manometer with a garden hose to the basement stairwell.

    1 PSI to water column [inch] = 27.6799 water column [inch]
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • jweob
    jweob Member Posts: 14
    Thanks for all the advice! I have a second pressure gauge I am going to install and if that confirms the cut out is too high I will follow @dabrakeman’s instructions to adjust the pressuretrol
  • jweob
    jweob Member Posts: 14
    @dabrakeman 's instructions worked like a charm. The second pressure gauge confirmed that the cutout was too high, but adjusting that screw 1/2 a turn brought it back to 1.5 psi cutout.