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Pressuretrol and Low Level Pressure Gauge

I recently added an Ashcroft 0-3 psi Low Level pressure to my system. Under normal operation the gauge reads 0.1 psi. To test it further I turned off some of the radiators and turned up the thermostat. The gauge was fairly erratic as the temperature built up and under pressure the gauge got up to 2.5 psi but the pressuretrol did not cut out. The pressuretrol settings are 0.5 cut in with a 1 diff. I can manually trip the pressuretrol but it won't cut out when the pressure rises. Does this mean that I need to replace the pressuretrol? And is it normal for the pressure gauge to get erratic as the pressure builds?


  • Vaporstat/Pressuretrol Test Gauge

    Nice clean setup!

    Use the link: http://www.heatinghelp.com/forum-thread/128249/why-do-Honeywell-vaporstats-suck-so-badly

    It will take you over to a discussion in the "Controls" section on Vaporstats/Pressuretrols. Read it and especially read the post on Gerry Gill's Vaporstat /Pressuretrol "Tester" . It's brilliant -so simple and dead accurate!

    - Rod
  • Brian_74
    Brian_74 Member Posts: 237

    I'm probably wrong about this but shouldn't the pigtails be turned 90°? I thought that the opening of the loop should not be visible when you're looking at the controls/gages. I am new to all this, so I am probably wrong, but I wanted to mention this. It is a nice looking setup.

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  • a small point

    i like having the low pressure gauge, and pressure controller on the same pigtail, if possible. that way if the pigtail plugs up, you can see the effect on the gauge pressure. with 2 separate pigtails, 1 could be unknowingly plugged. you could join the pigtail  tops of your present arrangement with t's and unions, so you have 2 protected routes for the steam to get to both gauge and controller, as i did on my boiler. in addition, each pigtail can be oriented "back to back" to resist temperature deformation which can alter  the vertical axis, and throw off mercury bulb type controllers. don't forget the 0-30 psi gauge must remain for code purposes-even though it really is useless for our purposes. --nbc
  • Nick_37
    Nick_37 Member Posts: 38
    Preesure Gauge

    The 0-30 psi gauge has not been removed and is located on top of the boiler. I add the low level gauge. The needle can be pretty volatile when the pressure starts to build up , is this usual?
  • Nick_37
    Nick_37 Member Posts: 38

    Rod, thanks for the link. So basically it sounds like all these devices

    have a problem with accuracy. What do you suggest I do next? Should I

    replace the pressuretrol or stick with what I have currently? If I need to replace it, what should I get?
  • Pressure Gauge Jumping

    How is your water line?..Is it surging?
  • Nick_37
    Nick_37 Member Posts: 38
    Pressure Gauge Jumping

    No the water line has not been surging. I boiled a sample of water from the boiler and it was not foaming. Even though I flushed the system a short while ago the water did get pretty brown after I had got the pressure up to 2.5 psi and stayed pretty constant. Mind you because I closed off some of the rads, I don't think the boiler had been taken up to that level of pressure for quite a while (if ever). The needle on the pressure gauge started bouncing after I had turned the thermostat down and let the boiler rest for a short while before turning it back up again to increase the pressure.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    The only time the pigtail orientation matters is when you are using controls with mercury switches. The movement of the pigtail will through the control out of calibration.

    These controls have no mercury, so no problem.
  • Brian_74
    Brian_74 Member Posts: 237
    Thanks, Paul.

    I didn't know that the orientation rule applied to mercury switched controls only. I appreciate you explaining this to me. The rule makes more sense now, too.


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