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I figured out how to calibrate a Pressuretrol!

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Fred
Fred Member Posts: 8,542
I don't know if anyone else is interested in calibrating their Honeywell Pressuretrol but after tinkering with mine, I finally figured it out!

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 to much, a fraction of a turn goes a long way towards getting it adjusted where you want it (not even an eighth turn). You may need to play with it to get it exactly where you want cut out to be but at least mine won't run pressure up to 3 Lbs when I have it set to cut-out at 1.5.
Seth RothenbergAnswermanLionA29AndrewB

Comments

  • nicholas bonham-carter
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    interesting procedure

    Thanks for this tip. But if you could get it to go to a lower range, that would be even more interesting!

    I'm sticking with my vaporstat!--NBC
  • Fred
    Fred Member Posts: 8,542
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    Not a Vaporstat for sure

    I didn't mean this was as good as a vaporstat. I may end up putting one on my boiler also but for those of us (and there are a lot of us) who still have Pressuretrols and have not been able to get them to act like a control device, there is a way to get it to cut out at the desired setting. My boiler typically runs at 7.2 oz. in a normal cycle but when it's below zero outside and I want to raise the indoor temp a couple degrees, to have it cut-out on pressure at 1.5 lbs (where I have it set) instead of it running all the way up to 3 lbs before the Pressuretrol cuts out is a big first step to getting things right.
  • SWEI
    SWEI Member Posts: 7,356
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    Assuming your description is accurate,

    it appears that Honeywell has a serious QC problem (as opposed to an actual design defect.) This could be a good thing.
  • BobC
    BobC Member Posts: 5,480
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    Monitor it

    That adjustment can work but sometimes it causes the pressuretrol to trip but never turn back on. Monitor it for several heating cycles to make sure it's working ok.



    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
    AndrewB
  • Fred
    Fred Member Posts: 8,542
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    Been Watching it

    I have been watching it for about 10 cycles now. The first cycle I adjusted it to much and it cut-out at about 12 oz. I turned it back a bit and set my thermostat for about a 6 degree rise and watched it as it cycled and made minor adjustments until I got it to cut-out right at 1.5 lbs. watched it cycle several more times and it cuts-out within an ounce or two of the 1.5lbs. cut-out, which I think is about as accurate as a Pressuretrol will get.
  • gerry gill
    gerry gill Member Posts: 3,078
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    good job Fred,

    i do seriously believe that honeywell has a QA problem with these controls. But you did good figuring that out.
    gwgillplumbingandheating.com
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

    Answerman
  • Fred
    Fred Member Posts: 8,542
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    Thanks!

    Thanks Gerry. That means a lot coming from a Pro like you!
  • LionA29
    LionA29 Member Posts: 255
    edited January 2017
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    Great Job @Fred.
    Thank you for sharing !!
  • ChrisJ
    ChrisJ Member Posts: 15,913
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    @Fred I missed this thread.

    I figured it out too, size the boiler properly and don't worry about the Pressuretrol's setting. :D
    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
    RomanGK_26986764589j a_2
  • Fred
    Fred Member Posts: 8,542
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    ChrisJ said:

    @Fred I missed this thread.

    I figured it out too, size the boiler properly and don't worry about the Pressuretrol's setting. :D

    Not everybody is blessed with your brain power @ChrisJ :D
    misterheat
  • ChrisJ
    ChrisJ Member Posts: 15,913
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    Fred said:

    ChrisJ said:

    @Fred I missed this thread.

    I figured it out too, size the boiler properly and don't worry about the Pressuretrol's setting. :D

    Not everybody is blessed with your brain power @ChrisJ :D
    I know, right?
    o:)
    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
  • JWise
    JWise Member Posts: 5
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    So if your boiler is indeed oversized, what is optimal pressure you are looking for ? What should I be looking for during a cycle.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,829
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    Try and stay under 2 lb. The lower the better but try and avoid short cycling. You have to keep the pressure low enough to keep water out of your dry returns. Water will rise up 2.31feet/psi above the boiler water line.

    Like everything in this business there is no direct hard answer. Always a compromise
    delta T
  • Fred
    Fred Member Posts: 8,542
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    @JWise , When I started on my system, I was hoping to stay under 1 PSI. By the time I got done, adding the ,main vents I needed, calibrating the Pressuretrol, and fine tuning everything that needed correction, my Pressuretrol once again became a Safety Device and not a Control device. I was fortunate that while my boiler was/is over-sized, my risers are 4 ft above the water line and I have a 5" header. Those things helped keep the steam dry and, I believe, aided with the Pressure issues.
    Before adding a 0-3 PSI gauge, my 0 - 30 PSI gauge barely moved but I was actually running at 7 PSI! The boiler ran almost constantly and the house was still cold. Radiator vents hissed like they were about to fly off of the radiators. I could hear gurggling and as @EBEBRATT-Ed said, above, the water in the boiler would back out into the wet returns. I use to use a 4 degree set-back which I stopped doing because it would literally take hours for the boiler to bring the house up to temp (and it is over-sized).
    I have since added a 0-16 ounce Vaporstat with the cut-in at 4 ounces and the cut-out at 12 ounces. I rarely ever have a heating cycle over 2 ounces of pressure and a heating cycle is about 20 minutes. On Design Days (0 degrees) I may have one or two heat cycles where the pressure reaches the 121 ounce level. I never have more than two short cycles per heating cycle and rarely more that two or three cycles during the winter when that occurs.
  • Dave0176
    Dave0176 Member Posts: 1,177
    edited December 2017
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    I made a little simple rig up to test pressuretrols. It works perfect and I’ve yet to come across a factory pressuretrol that’s set right.
    DL Mechanical LLC Heating, Cooling and Plumbing 732-266-5386
    NJ Master HVACR Lic# 4630
    Specializing in Steam Heating, Serving the residents of New Jersey
    https://heatinghelp.com/find-a-contractor/detail/dl-mechanical-llc

    https://m.facebook.com/DL-Mechanical-LLC-315309995326627/?ref=content_filter

    I cannot force people to spend money, I can only suggest how to spend it wisely.......
    CLambCanuckerRomanGK_26986764589
  • guzzinerd
    guzzinerd Member Posts: 244
    edited January 2023
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    Very helpful older thread.  Just wanted to just add that on my L404F, the adjustment screw is a small flathead accessable behind round chrome hole cover on back.


    Bryant 245-8 2-pipe steam in a 1930s 6-unit 1-story apt building in the NM mountains.  26 radiators heating up 3800sqf.