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Low PSI gauge installed on tee with vaporstat with gauge reading well below zero between runs.

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Is this gauge functioning properly for a one pipe steam system. Vaportat set at 14 oz cut in and 1.5 psi cut out but after
deep set back gauge needle way below zero. Is that a vacuum? Is this supposed to occur?

Comments

  • BobC
    BobC Member Posts: 5,479
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    AS the steam condenses it will form a vacuum until the air vents cool and begin to open.

    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
  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    One air vent on far small radiator hissing loudly and releasing air
    at this time
  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    Ok this is expected thank you
  • nicholas bonham-carter
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    If you can hear a radiator vent, then you have insufficient main venting.--NBC
  • icesailor
    icesailor Member Posts: 7,265
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    Sometimes it's hard to tell if a vent is hissing air pressure or hissing because it is sucking air in. Spit on your finger and hold your finger over the hole. If the spit bubbles, it's blowing. If the spit gets sucked away, its sucking.

    A third world, shade mechanic's method of checking for the suck or blow.
  • Captain Who
    Captain Who Member Posts: 452
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    Vaportat set at 14 oz cut in and 1.5 psi cut out

    I guess you have the 0-4psi model Honeywell vaporstat, with "main" set at 1.5psi and "differential" set at 10 oz/in2? The differential is subtractive on this model, so that would give a cut-out of 1.5psi (24 oz/in2) and a cut-in of 24 - 10 = 14 oz/in2.

    Just trying to find out if you set it right.

    Which model # of vaporstat did you buy?

  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    The model is L408J1017 It is a low pressure 0-4 psi model
    It appears that my boiler is oversized and I need more venting.
    Also need to insulate pipes. Augh
  • Fred
    Fred Member Posts: 8,542
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    Does the gauge stay below "0" when you take it off of the pigtail? If so, you probably just need to recalibrate it. There are two tiny screws on the face of the dial, one adjusts the dial to the + side the other to the - side. Use the one for the + side and readjust it to "0". If the dial goes back to "0" when you take it off of the pigtail, then you actually have a vacuum.
  • ChrisJ
    ChrisJ Member Posts: 15,784
    edited December 2014
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    If the gauge is staying in vacuum after the boiler runs and re-zeros when you remove it from the pigtail do not recalibrate it. There has been at least one other member that kept doing this and broke his gauge because it kept getting more and more offset.

    I had constant problems with my gauges ending up reading a vacuum after running and then staying there even during the next cycle and my final solution was to remove the pigtail. While I cannot recommend doing this for a safety device like your main high pressure limit I am using it for my low pressure gauge and secondary low pressure high limit. My main pressuretrol which is there only for safety is still on a pigtail.


    Please see the thread I started on the subject. My gauge being both slow and usually reading a vacuum is something I had fought with since 2011.

    http://forum.heatinghelp.com/discussion/152691/going-commando/p1
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    It definitely was a hissing blow from the radiator. The hissing air was not hot but the radiator was all fins warm.Probably need more venting.Will finish venting this week
    Can I recalibrate the low pressurw gauge by removing cover and leaving it connected to tee?
  • Captain Who
    Captain Who Member Posts: 452
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    Lets take things one thing at a time. Did you do what was suggested and remove the pressure gauge when it was showing a vacuum and see if it goes to zero?
  • Captain Who
    Captain Who Member Posts: 452
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    Make sure the boiler is switched off when you do so. You never really said under what conditions it shows a vacuum. We need more information really.
  • Fred
    Fred Member Posts: 8,542
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    You can recalibrate the Gauge with it on the Tee but you really should first know if it needs to be recalibrated or if there truely is a vacuum. If there is a vacuum, when that breaks, the gauge will need to be recalibrated back to where it was because it will show some pressure when there isn't any and your readings will be off by whatever the adjustment was.
  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    ok, so take off and see if needle moves to zero. then recalibrate. BTW The higher range pressure gauge 0-30 psi on boiler never moves below zero. It is directly connected to boiler without pigtail. The low pressure gauge I installed on tee opposite vaporstat on pigtail does read below zero at times between runs. I was told that the lower pressure gauge would be more accurate but I am finding these below zero readings between runs and wondering about the low pressure gauge accuracy.


































  • Captain Who
    Captain Who Member Posts: 452
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    What gauge did you buy? I have a 0-3 psi gauge and since 0 is on the peg, I never see if it wants to register vacuum. However, when my pressuretrol is cycling the boiler, it cuts back in at 0.5 psi every time. By the time the flue damper closes and fires the gas valve it has coasted down to 0.25 psi, but that's as low as she goes.
  • Captain Who
    Captain Who Member Posts: 452
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    Oops......."by the time the flue damper OPENS" (not closes). The electrical switch inside the flue damper closes though (that must've been what I meant to say lol).
  • icesailor
    icesailor Member Posts: 7,265
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    Compound pressure gauges (-30-0-+30# PSI) are like aircraft altimeters. When you change the barometric pressure, they go up or down in altitude. When compared to a known working barometer and fixed altitude, if the devices don't coincide, the altimeter is junk, and not to be flown with. You might fly into the ground. You can buy or borrow inexpensive compound gauges. If the suspect gauges reads zero, and you suck or pressurize it, and it doesn't go back to zero, don't trust it. That gauge is older than you are.

    If you replace it, be sure it is a compound gauge. If it is vacuum only, and it goes to pressure, you will destroy the vacuum part of the gauge.
  • Fred
    Fred Member Posts: 8,542
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    ok, so take off and see if needle moves to zero. then recalibrate. BTW The higher range pressure gauge 0-30 psi on boiler never moves below zero. It is directly connected to boiler without pigtail. The low pressure gauge I installed on tee opposite vaporstat on pigtail does read below zero at times between runs. I was told that the lower pressure gauge would be more accurate but I am finding these below zero readings between runs and wondering about the low pressure gauge accuracy.

    Because you gauge goes below zero, at times, doesn't mean it is not accurate, it may mean that, at times you have a vacuum. That vacuum could be system wide or simply in the air space between the pigtail loop (where water resides) and the gauge. That is not an inaccurate gauge.
    That 0-30PSI gauge never moves below 0 but it also never moves above 0. That's not a sign of accuracy.


































  • rrwitherspoon
    rrwitherspoon Member Posts: 104
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    Yes, the 0-30 psi gauge does move above zero. It goes to 1.5-2 psi
    and cycles down with vapostat but It never goes below zero.