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Low water pressure switch for hot water boiler.

Hello, have a 70's era American standard hot water boiler. Works great but there is no low water cut off switch. I see plenty of these devices for sell but to me they only tell if there is no actual water inside the boiler. Which certainly would be protection but looking for something else to alert me well before it gets to that point.  I have seen low water pressure switches referenced on the internet to shut off when it is below a certain pressure, but only reference to it, no part numbers or manufactures. Does anyone no the exact name or such a device and where to purchase one, or any other thoughts. BTW, the system runs between 12 and 15psi if that matters, so ideally, anything below 10 psi would shut of  the system? Below is a picture I found off a web site and the description.

<em>An adjustable safety device which prevents boiler operation when the system pressure falls below the preset level, usually 5 PSI. It helps prevent boiler coil and heat exchanger damage by preventing the boiler from firing during an unsafe low water pressure condition</em>.

Thanks in advance. John


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839

    and you are correct, you will lose pressure before you lose water level, but you have to make certain that everything else is set up correctly, or you will get into nuisance lockouts.

    The pump(s) should be pumping away from the boiler and the expansion tank connection, and the pressure switch should be connected at the same point as the expansion tank.

    In lieu of that pressure switch, you can get a double throw adjustable pressure switch, which would allow you to stop the burner and start an alarm, or also turn off the pumps.

    Check Graingers for an adjustable pressure switch. The switch you show is used on a BUNCH of modcon boilers.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • johnincincy
    johnincincy Member Posts: 2
    Found what I needed.

    Thanks Mark for pointing me in the right direction. Took me a few minutes to find what I needed. Graingers has more selection than I could have ever imagined. I will feel safer when I get it installed. John
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