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Steam Boiler Flooding

AlchemistAlchemist Member Posts: 25
Hi all,

Here's the situation (and I'm a novice, btw).

Medium sized residential steam boiler in a 3 story, 5 unit condo complex. The boiler heats intermittently, unevenly, and seems to be flooding on a regular basis.

There is a condensate return tank with a boiler feed pump. Into the condensate tank run the condensate return line and an automatic water replacement feed from city water. The automatic feed does not have a pump, as far as I can tell, but has several valves, the last being a reducing valve.

The overflow vent from the condensate tank regularly dumps a lot of water on the water. Not just a bit of overflow, but many gallons. One of the contractors I've had look at said the whole system shouldn't every return more than about 10 gallons.. However, he took 35-40 gallons out one day.

It takes several gallons to run clean.

Here is the confusing day I observed the following. Following tenant complaints, I went over one day to reset the thermostat to 1-2 degrees higher. The boiler was not fired up, but the feed pump was running continuously (for the 15-20 minutes I was there-at least sounded like it was running). I made a note of it but didn't really understand what I was hearing/seeing. BTW, the condensate return tank during this whole period was about 1/3 full.

Fast forward 6 hours and a tenant tells me the pump still sounds like it is running. The boiler hasn't fired in about 12 hours.

Fast forward to the next day. I go back, the pump STILL seems to be running. Boiler still has not fired at all. Not really knowing what I am doing, I flip the power off to the feed pump. It shuts off. I turn the power back on. The pump does not restart, but the condensate return tank fills QUICKLY with water and overflows several gallons on the floor before I hear the pump again. The boiler then fires amazingly and starts to heat the building.

The floor is eroded in the exact pattern that the water overflowed to. This pattern, or something similar, seems to be happening regularly. To contractors (perhaps knuckleheads) have no idea what is happening. I described this incident to one of them, he thinks I imagined it. He said it was not possible.


Does this make sense to anyone?

As an aside, all the steam traps in the building have been replaced. The trap on the condensate return line has been replaced. One of the "pros" said the system probably needed to be vented. This I cannot speak to, however the original system was steam heat and the building was built in 1911.

Thanks in advance!!



  • Repeated flooding

    The first thing to do would be to check the operating pressure, and see if it can be stabilized under one PSI. You probably have an old vapor system, whose traps, and vents have problems with higher pressures. Installing a 0-3 PSI gauge will show you what your pressure is. Have the pressuretrol removed, and clean the pigtail. A vaporstat will probably be needed for the future.

    While you are there, test the LWCO, and ensure it will cut off the burner when you flush it. The next step would be to run off the city water make up feed with the inlet valve, and check on the operation regularly in the next few days.

    Post a few pictures of the boiler, and it's piping, and the radiators, and valves, and traps.

    What is your location?--NBC
  • AlchemistAlchemist Member Posts: 25
    Repeated Flooding

    Thank you for the response. I live in Minneapolis, MN.

    The last boiler technician I had working on the system did (I believe) do some of the things you suggested. Unfortunately, until I read THE BOOK this week, I had no idea how anything worked and was not there when he did the work. We are sort of maintenance by committee in a small association.

    I do know that there used to be a pressuretrol that had a screw for both main and differential pressure. We also had a pressure gauge. Apparently he thought the gauge wasn't working. The current pressure setting is at 5 psi (??) with no gauge. Unless I looked at it wrong--or it is a vaporstat where the setting is in different units--it is as 5 psi. This makes no sense as the guy preached to me at first, when the main problem was water hammer, to turn the pressure as low as possible (I now understand to be the right thing to do).

    I will post pictures on Tuesday.

    Last question until Tuesday. Can anyone explain, in laymen's terms, what happened when I shut the feeder pump off and the condensate return tank immediately filled and overflowed gallons of water onto the floor. See my post above for a full description.

    I just can't make any sense of that.??
  • do post some pixs

    And I will be up in TC next month for Wild games!
  • in meantimes

    Crank that pressure down to 2 psi cut out, .5 cut in til we see some pictures
  • gennadygennady Member Posts: 680
    boiler feed tank

    feed pump mounted on the tank is controlled by low water cutoff /feeder combo, or similar device mounted on the boiler and in case of low water conditions starting the pump to feed boiler to proper level. Also on the tank you have to have float switch preventing pump from operation in case of low water level in the tank, and same switch or additional one to turn on solenoid valve mounted on water feed line feeding tank, not he boiler directly.

    hope it helps
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
  • gennadygennady Member Posts: 680
    edited December 2013
    shutting feeder pump

    do you have working check valve on feeder pump? it is possible that condensate back flows from boiler to the tanks trough feed line if check valve is broken.
    Gennady Tsakh

    Absolute Mechanical Co. Inc.
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