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very old boiler, pressure relief releasing water.

astro46 Member Posts: 1
Likely the original boiler (1926, "The Capitol" size: 25-5), originally on coal, then oil, now running on natural gas, in Chicago, brick 2 story, 2 apt building. About five years ago the expansion tank developed a leak, so I replaced it with an ETX 15 diaphragm expansion tank. After seeing the pressure relief valve releasing small amounts of water constantly during heating season for years, I took it upon myself to lower the reducing valve pressure, eventually to turning it out 2.5 turns. Since then no problem with releasing water, and the system, as far as I know, has worked fine.

This fall I noticed that the Bell and Gossett Series 100 circulator pump bearing housing had water in it. I replaced it end of oct. After that I get a short squeak from housing when pump shuts off. And, pressure relief was dripping for weeks. I tried opening it numerous times thinking maybe rust got stuck in when I turned water back on and flushed pipes through the pressure relief valve. Not getting it to stop, and not knowing if it or the reducing valve failed in the process of turning water off and on, I have replaced both the reducing and pressure relief valves. For about a week after that, water continued to dribble out of pressure relief, so I continued to open it to release move water, hoping to clear it. Water no longer continually dribbles from the pressure relief, but it does release water when heat comes on. maybe 1.5 gal over the course of a day.

I tried unscrewing the reducing valve adjustment 1 turn. I have also removed the expansion tank and checked its pressure. 8# the gauge said. I put a pump to it and increased it to 11# and reinstalled it. Pressure relief still releases water. The boiler pressure gauge, after heat being off for 4 hrs shows 12#.

Question is: shall I continue to lower the reducing valve pressure, maybe another 2.5 turns, so it is similar to previous one? Increase expansion tank pressure? Is the current recommendation of 12# pressure not applicable to older systems because maybe the pipes are larger or burners different or ....? Anything bad about having a lower pressure in the system? (With the lower pressure of previous reducing valve, I could still get water (bleed) all the radiators on both floors.)

bonus question: Some sources have suggested that the short squeaking noise at motor shutoff (not all the time) is caused by failing motor mounts. this squeak wasn't happening previous to bearing housing replacement. Local B&G sales reps said if the mounts were bad the coupler would be breaking. That the noise is likely coming from a not quite properly formed sleeve bearing. It may go away, Or I can get used to it. Or replace it under the one year warranty. What do you think about the squeak noise?


  • Steamhead
    Steamhead Member Posts: 16,889
    I looked up your boiler and it seems to be fairly large- around 2200 square feet of radiation which would equal roughly 330,000 BTU per hour. If true, a 15-gallon diaphragm tank is way too small. This would be why the pressure is rising this way.

    What were the measurements on the original tank?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 15,614
    First find the presure you need to run at.

    Take the height of your building and run the pressure in the system at building height in feet di.vided by 2=psi + 4 psi so for example a 50' building/2=25+4=29psi. If your building is less than 25' you can use the standard pressure of 15 psi.

    Remove the expansion tank fro the system and pressurize the air side of the tank to the required pressure. Reinstall the tank and adjust the water feeder to the same pressure fill the system. They need to match

    When the pressure comes up your pressure rise (from cold water to hot water) shouldn't exceed 8-10psi. If it does your expansion tank could be defective, too small(as @steamhead mentioned) or your feeder is leaking by
  • Alan (California Radiant) Forbes
    Regarding the replaced bearing assembly, did you add any oil?

    As you can see by the picture below, most of the oil gets added to oil cup #1 which is the bearing assembly.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Ironman
    Ironman Member Posts: 7,379
    An old boiler that was once coal fired connected to large gravity flow pipes? An x15 tank is not just way too small; it's utterly ridiculous.
    The Amtrol quick sizing app recommends at least an SX-40V. I say at least, because with old large piping, the actual water volume of the pipes, rad's, and boiler is needed for proper sizing.
    Do you know the size of the old compression tank which was removed?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.