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1:05 pm 10/23/2012

I am working on a boiler problem at the Federal Building in Springfield, Illinois.

I have 3 Weil McLain #94 boilers with a vacuum return system.  All 3 boilers have vacuum breakers on them.  When the vac pump is running, it sucks all the way back to the boiler vac breakers.  Should these boilers have vac breakers on them?  Based on the articles I have read on the Wall, the answer is no.

The boilers have been replaced and a make up system has been added. When I turn the vac pump system on, I can hear water sucking on the receiver tank of the make up water.  Base on the articles I have read on the Wall, there should be a motorized valve in the vent line to the receiver tank. May I thinking straight?  Can this be a common motorized valve in the vent line that will close when none of the 3 make up water pumps are not running but will open when any one of the make up pumps need to add feed water to the respective boiler?

Final question.  I know one of my vacuum pumps is shot by the sqealing and whining.  If I replace them should I resize them larger to allow for any leaks that may be in the older system now. 


  • ttekushan_3
    ttekushan_3 Member Posts: 958
    adjust vacuum level against vacuum breakers

    It seems to me that the vacuum pumps are adjusted to a lower vacuum pressure level than the adjustment on the vacuum breakers. I presume that you have adjustable vacuum breakers and can adjust the breakers to a lower pressure (deeper vacuum) and/or adjust the vacuum pump levels a bit higher.

    Letting large quantities of air directly to the boiler will cool the steam, cause heat distribution problems and add so much corrosive oxygen to the boiler as to be destructive, even if using oxygen scavenging boiler chemicals.

    The boiler feed tank shouldn't be developing vacuum unless there are also overflow traps on the boilers piped directly to the feed tank rather than the vacuum return reservoir.

    What kind of vacuum pumps are there? They should be quite rebuildable. Squealing bearings can be replaced. Is it a liquid ring system (e.g. Nash Jennings)? If so, is the vacuum pump trigger on the reservoir set so that the liquid ring remains "wet"?

    Or is it a vortex type vacuum system (e.g. Domestic Vacuum Heating) with a cast iron receiver with pump(s) on it that run throughout the heating cycle?

    You really shouldn't have to throttle the boiler feed tank if everything is set up the way it's supposed to be, regardless.
  • rwangard
    rwangard Member Posts: 2
    found a problem

    The problem turned out to be that a new condensate return pump was added to our system to accommodate steam heat exchange for building hot water heating loop.  The condensate return was piped into the top of the condensate holding tank, rather than into the vac return system.  Also found that one of the vac pump was trashed because of high return, replaced pump and added an aqua-stat to monitor return temperature in case a FT trap goes bad, it will shut down the vac pumps.
This discussion has been closed.