Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Help identify pressuretrol

Hello all,   I am turning to the masses in hope of finding the manual for my pressuretrol, Johnson Control (penn) #P47AA-25,   Weil Mclain Part #510-312-106, Cross ref # PA404A1033.  All searches of the markings returned different pressuretrols, none of which matching mine, which is pictured below.  Thanks for any info you guys can provide.


  • furnacefigher15
    furnacefigher15 Member Posts: 514

    Do you need to know about it?
  • cwaz
    cwaz Member Posts: 22

    I am unable to set the "cut in" or "cut out" pressure any lower then is photgraphed (roughly 1psi and 3psi respectively). When I turn the adjuster and lower the pressure settings on the control, the boiler will run for a while until the pressure builds and causes the contacts on the pressuretrol to open, stopping the burn.  At this point the contacts will remain open (even well after the boiler shuts down and the pressure is relieved), keeping the boiler off.  The "cut in" and "cut out" it is currently the lowest possible in order for the pressuretrol to close its contacts when the pressure drops.  So I was hoping there was a calibration screw within the pressuretrol to "re-zero" it out and allow me to drop the differential from the current 2psi.   

     I have ordered a low pressure gauge in hopes of getting a better idea of what is really going on since the 30psi gauge and pressuretrol can be grossly unreliable. 

    I hope I was able to explain this well.  Thanks for any info. 
  • Saverio DeLuca
    Saverio DeLuca Member Posts: 5

    The pressuretrol settings of cut-in 1 psi and cut-out 3 psi are within a normal range. There should be another setting (usually found inside the cover) which is the differential setting and should and probably already is set at 2 psi which should give you a cut-out of of approx. 3 psi. Cut-in 1 psi + differential 2 psi = cut-out 3 psi approx. However, you're problem appears not to be your pressuretrol but the pigtail pipe that the pressuretrol is mounted onto. The pigtail is usually a 1/4" loop pipe that the pressuretrol is screwed onto (sometimes it's a straight 1/4" pipe). It's a very common occurance that the pigtail pipe gets clogged with sediment preventing free flow to the pressuretrol causing the condition you're talking about and/or it will make the boiler short cycle whereby the boiler will shut off before reaching the cut-out setting causing a condition of not enough heat. It appears the pigtail has to be removed and replaced with a new pigtail. When replacing the pigtail it's best to use a brass pigtail, it can stay clean for a longer period of time. Like to know how it works out for you.
This discussion has been closed.