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replacement for a honeywell pressuretrol controller

Hi guys, I like many others have a Honeywell PA404A for a Weil Mclain EG45 150,000 btu natural gas fired steam boiler. And like others find the pressuretrol inaccurate. I have set it for .5psi cut in and 1.0 lb differential cut out however it operates at approx. 2.4 lbs cut out and 1.5 lbs. cut in. I know you can no longer get the mercury type controller. So what other manufacturer is available for this low voltage system and how accurate are they. This unit is having my system lose water due to the high pressure. I am located in queens, N.Y. City.


  • Abracadabra
    Abracadabra Member Posts: 1,948
    You can use a vaportat, but your boiler isn't losing water due to 2.4psi of steam. There's probably a leak somewhere
  • EzzyT
    EzzyT Member Posts: 1,258
    I doubt the pressuretrol is causing the system to spike up to 2.4 psi most likely the cause of that spike is lack of steam main venting and properly size radiator vents if the system is a one pipe system. Improper near boiler pipe will cause the pressure to spike too, as @Abracadabra mentioned you losing water is most likely do to a leak.
  • Fred
    Fred Member Posts: 8,541
    You don't need to buy a replacement for the Pressuretrol. Spend that money on main venting or finding out where the water might be going. Do the vents leak steam? That might be a source of water loss.
    Follow this procedure and you can re-calibrate your current Pressuretrol. It is a simple process.

    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.

    A couple of guys have had a problem turning that hex screw because of a thick layer of lock-tite on it. They have overcome that issue by using a soldering iron to lay on that screw long enough to begin to melt the lock-tite.
  • robertj
    robertj Member Posts: 3
    Thank you gentleman for your quick and informative responses. I thought the 2.4psi would be the cause of my system losing water. Apparently it's some small leaks at valves or vents which I can tell you are not visible. I have to add approx. 1-2 quarts of water to the boiler each week. I'll have to check the radiator valves for steam leaks at the valve stems and pipe connections. All of these are original to the home and 75 years old. No visible leaks from the steam or return line (return line is above ground and visible). Any additional insights would be welcome!
  • Fred
    Fred Member Posts: 8,541
    You can loose that amount of water from just one bad vent.
  • robertj
    robertj Member Posts: 3
    thanks fred.