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Setting pressuretrol

Ed_49 Member Posts: 7
Thank you all for your responses! Does turning down the pressure, to .5 psi or so, work only if vents are installed on the mains ? Is it possible that without these vents I will have to keep the pressure somewhat higher?


  • Ed_49
    Ed_49 Member Posts: 7
    How to set pressuretrol

    I have a newly installed Weil SGO5 boiler. 2 story house, 14 radiators. We have lots of hissing, gurgling, spitting, banging from the radiators. Much more than with the old bolier. From reading here it seems our pressuretrol may be set way to high. We have a honeywell pa404a. On the front there's the cut-in setting the range goes from .5 to 9 psi or .1 to .6 kg/cm. Ours was set at .3 kg/cm which is about midway between 2 and 5psi. I can turn this down using the screw at the top of the pa404a. If I put it down to 2 or lower is there a corresponding change somewhere else to make? I read here references to the cut-out, differential, etc. but only see how to set the cut-in on this pressuretrol. Thanks.
  • Ed_49
    Ed_49 Member Posts: 7

    Can anyone help?
  • pressure too high?

    why not call the installer, to have him show you how to set the pressure down below 16 onces? ask him why he set it so high. you probably should get a vaporstat.

    also get him to show you other parts of the system, such as vents.

    is this 1-pipe or 2-pipe steam? do you have dan's steam book [lost art of steam heating] , available here? it would be probably the best investment you could make in 2009.--nbc
  • Ed_49
    Ed_49 Member Posts: 7

    It's a one pipe system. I'll try the installer but thought I might get better help here. Also, no vents on the mains, just on the radiators. Never were any on the mains as far as I can tell.
  • main vents

    the radiator vents are not going to be able to do the work of the main vents. if it's a very old system , in its youth, it must have had some arrangement for venting the mains and returns. the boiler will have to work harder get the air out using only the radiator vents, than with main vents.

    have another look, and see if there could be plugged openings which once held vents [either close to the boiler, or after the last radiator]. they may be difficult to locate, but they surely were there at one time.--nbc
  • David Nadle
    David Nadle Member Posts: 624
    Try this

    First, my question is, why did the installer not leave you the instructions? If you google the part number you may be able to download a manual.

    Usually there is a white thumbwheel inside the pressuretrol that sets the differential. You have to remove the cover to access it.

    Try setting the cut-in to 0.5 psi and set the differential to 1 psi.

  • Bill_110
    Bill_110 Member Posts: 52

    I just had a new boiler installed with this Honeywell Pressuretrol. The installation manual said to set the cut in at .5 and the differential at 1 for a typical system. For some reason the guy installed it set at nearly 2 with a differential of 1.1. I asked him about this and he offhandedly mentioned I could "play around with it" if I wanted. I doubt if a lot of these guys even know or care what the ideal setting is, or whether your paying a lot more on your heating bill because of their lack of interest.

    I let it run this way for a while. Then I gradually lowered it to bout .5 cut in by turning the screw on top. Then I opened the thing and turned the little differential wheel down to one. I soon found out what Holohan was talking about in those missives about cranking down the pressure and creating dry steam. The radiators heated up a little sooner, but the real difference was that they got much hotter for the same run time as before, and they stayed hotter much longer radiating useful heat. This dry steam thing is no humbug. I should point out too that my system could be much improved in this regard when correct near boiler piping gets installed. Even with the less than ideal piping, adjusting down the pressuretrol gave me a lot more useful heat.

  • better help?

    you will certainly get better information here, and in time will become more knowlegable about your system. also, you will be able to diagnose [and repair] many problems yourself--nbc
  • David Nadle
    David Nadle Member Posts: 624

    Start low, then work the differntial up if you find you are not filling the last radiator on a very cold day. I bet you'll be fine. As Dan says, the Empire State Building uses 2 psi. Do you think 1.5 psi won't work in your house?

    Adding main vents will help get the radiators filled at the same time, and more quickly, and more quietly. Definitely consider adding them.
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