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.

Boiler questions

Alex265 Member Posts: 41
I have a very old Burnham boiler with bad around piping which however did it job for the last two seasons (it's in the apartment of a 2-family house). It has 2 Honeywell pressuretrols (one of them on the float-type water level control) and an old 30 PSI pressure gauge which is connected without a pigtail. It's been off since about April. Recently I changed the main vents on the 2 mains and fired it up to see how it works. I have couple of questions about the results.

1. The main vents started hissing very soon, after about 3 minutes when the risers weren't even hot. How is this possible? The boiler is small but could it really boil the water so fast? Water level is fine.

2. Soon after that the pressure started rising according to the gauge, and after 10 or so minutes went up to 25 PSI! Then stopped, and after I turned the boiler off, it took the gauge about half an hour to return to 0. There was no banging. There were no signs of high pressure as far as I can tell. When the gauge still showed about 20 PSI, I went upstairs and unscrewed the air valve from one of the radiators expecting a strong stream of steam out of it, but there was nothing. How is this possible? Where is the pressure? Can the pressure gauge be busted?

Pressuretrols not doing their job don't worry me for now, I will adjust them when I'm clear about the pressure level.


  • Unknown
    Pressure guage

    That 30PSI gauge has gone south. You can buy a replacement for it but it would be better to add a second 0-3 or even a 0-2PSI gauge so you can really see whats going on. The system should be operating at 2PSI or less for best efficiency, my Burnham v75  maxes out at 0.8PSI. You can mail order these from "The Gauge Store", the 0-3PSI gauge I used can be seen at - http://www.gaugestore.com/prodinfo.asp?number=33020

    These low pressure gauges need a syphon loop to isolate the gauge from the live steam but your pressuretrols probably have them so you can T off those. The attached photo shows my setup with the vaporstat and 0-3PSI gauge T'd off the syphon loop, you can see the original 0-30 PSI gauge behind one of the greenfield cables. I will be installing a 1/4" universal joint the next time I take this apart so I don't have to mess with the wiring to take the assembly off.

    good luck,

  • Alex265
    Alex265 Member Posts: 41
    Thanks for your reply

    I already ordered a replacement 0-30 PSI, and when I confirm that the pressure is normal, I'll add a 0-3 PSI gauge (I did a setup similar to yours on my other boiler).

    It definitely didn't look like there was 25 PSI in the system... My old 0-30 PSI gauge is connected exactly like yours, directly into the boiler without a pigtail. So, it's all right to not have a pigtail for 0-30 PSI? I kind of thought that this was what made it go south.
  • Steamhead
    Steamhead Member Posts: 16,832
    Every gauge and pressuretrol needs a pigtail

    and every pigtail should be brass. Iron pigtails rust up and clog.

    Some gauges have an "internal syphon" which does the same thing as a pigtail, but if an internal unit clogs it cannot be cleaned. A standard type gauge and external brass pigtail is the way to go.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
This discussion has been closed.