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HydroTherm VGA-200 steam boiler with feed pump

Hello fellow steam boiler owners,

My wife and I bought our first new (old) house this past summer. Built in 1913, it came with the original one-pipe steam heating system and an approximately 20 year old steam boiler with a 2 year old boiler feed pump and condensate tank. Pictures attached for your interest.

I don't know why I have a boiler feed pump because I think my pipe dimensions would be good for gravity return. It's an 1800sqft house with 11 radiators and dual loop mains that are only around 30 ft long each. But anyway it came with the tank and pump. My issue with the pump is that when it runs, all the air rushes back through the radiator vents, causing a loud hiss. I was told this is the new water entering the boiler and collapsing the boil, causing the steam to retreat and let some air back in the rads. After about 30 seconds after the pump stops its 5-6 second run, the vents start to pant for about 30 seconds. The water in the gauge glass also rises to about the top of the glass and bounces around for a while and eventually settles out and starts coming back down. I think this occurs when the water reaches a boil again after the condensate was pumped back into the tank. FYI, I know the gauge glass looks a bit dirty but that's some old staining, the water is pretty clean (ph 8) and I blowdown the floats every week. There is a water autofeeder that goes into the feed tank that runs when the tank level is low. It never turns on more than once every month or so. No leaks in the system.

What can I do to reduce the in-rush of air coming back into my rads when the boiler feed pump runs? Is there anything I can do about the panting of the vents after the pump stops as well? I noticed I do not have any kind of throttle valve on the pipe from the pump back to the boiler. Would installing one (what kind)? lengthen the run time of my feed pump and lessen the air in-rush back through the rad vents?

I think the F&T traps are working fine. I don't have any steam coming out of the tank air vent and no backup of condensate.

This boiler feed pump sure makes for an interesting behaving system! Maybe next time I'll tell you about the fun I've had with this boiler (I can see why Hydrotherm dropped their steam boiler product line...)

Thanks for the tips,


  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    Two thoughts... firs,t although you didn't ask about it, I'm not really too happy with the way that boiler is piped...

    Second, is there any way you can find out why that condensate receiver is there at all? And why the F&T traps exist? Neither should be necessary if the system is properly piped...

    You might be able to remedy the feed pump killing the steam by throttling it way down -- like, way down.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,544

    You need to install two air vents on the condensate return lines on the inlet side of the two F & T traps. You can install them in the two unused inlet ports on the steam traps. The air will be pulled in there instead of up in the house.

    You may be able to get rid of the pump by doing some repiping would need to see the whole system
  • heatless_in_Winnipeg
    Thanks Jamie. Yes I thought the near-boiler piping is a bit odd but I don’t know how it’s supposed to be for a boiler feed pump, aside from the absence of a Hartford loop, which I don’t have because of the pump. I guess my equalizer also isn’t an equalizer now as well. 

    The pump is 3/4hp, probably way oversized. It was just replaced by the previous owner so I’m not changing it or the tank for now. What kind of valve should I get added to throttle the flow way down?

    Thanks Ed. That’s a clever idea. I guess I would need some pipe fittings to go out and up to a 1/4 NPT when I could install a main vent. I thought of doing that before to increase my main pipe venting rate, but the F&T seem to vent my short mains fairly fast so I threw that idea on the back-burner. 
    JUGHNE Member Posts: 11,062
    I had the same problem with smaller boilers.
    Even 1/3 HP was too much...too quick.
    It would knock the steam in the boiler down dropping the pressure.

    I added a bypass tee/pipe to the pump discharge and then tee into the vent pipe.
    I did include a ball valve in that bypass pipe but can leave it fully open.
    This returns most of the water right back into the tank

    Then in the line to the boiler a "plug valve" was added.
    It is a 1/4 turn iron body with brass plug inside for adjustment.
    The plug valve was a salvage take out from gas piping, sometimes referred to as an "I-bib" or some local term.
    It requires an adjustable wrench to move the plug.
    You could use a ball valve but it will distort the ball eventually and not be movable.

    The flow was slowed down to just keep up with water level dropping.
    You do not want the LWCO to shut the burner down each pumping.
    The pump will run longer for each call for water.
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    What @JUGHNE said -- with one addition. This is one of the few situations where an ordinary globe valve can be used to advantage as a throttling valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • motoguy128
    motoguy128 Member Posts: 393
    200k with 11 radiators and 1800sqft is on the edge of oversized. But even then I’m baffled why it needs a feed pump system with such a small header. I have a 90’ 3” header with the same size boiler with only 9 radiators feeding just my upstairs and no need for a pump or condensate storage. Pressure never exceeds 1 psi before all radiators are full of steam which almost always satisfies the thermostat prior to that since it’s only upstairs. (Converted downstairs to hot water, so it carries 80% of the house load).

    Level might drop 1” while firing but it never causes the feeder to falsely trip.

    I would guess your venting is too slow and the boiler pressure rises and pushes the water out of the boiler. So the expensive condensate pump system was a solution to that symptom.

    That boiler does have a single supply only and I’ve noticed it tends to really drop the water level while firing.

    TO stop the whistle on shut down you need more main vents like Gorton 2’s that have a float and open under vacuum. Or you can add a vacuum breaker like I have.
  • heatless_in_Winnipeg
    Thanks everyone. I'll talk to a contractor about either putting in a bypass back to the tank air vent pipe like @JUGHNE did with some valves to adjust the flows, or about just putting in a globe valve in the pump discharge line to the boiler to try to throttle it back that way. Not sure if the latter will be good enough because I think that pump is at least 10 times higher flow rating then it should be after reading Weil-Mclains recommendations in their install manual but it's the easy option to try first. I could add some more vents in parallel with my Hoffman F&Ts off of the steam side taps but I'd rather fix my boiler pump steam-killing issue directly.

    As for my radiator venting, it was almost all Hoffman 40s when I got the house (with two MoM 5s on the biggest rads) but I replaced a bunch on the larger rads with Gorton 5s and 6s. I know I should stick with one brand after reading more but I don't think it's worth to the money to replace a bunch of vents that work fine.
  • pedmec
    pedmec Member Posts: 975
    first of all are you sure its a one pipe steam system? do you know the difference between a one pipe and a two pipe system. other than the air vents on your radiators the condensate return piping is set up for a two pipe steam system. that would explain why you need the pump. you don't have any leftover steam pressure in the returns to help the condensate get back in the boiler before stacking in the returns.
    if it is a one pipe steam system you need to remove the f&t traps from the returns and create a return manifold with a hartford loop and connect to the existing return. get rid of the condensate pump. put two main vents 6" away from the end of mains and on minimum 6" nipples
    there is no place for f&t traps on one pipe steam for residential. they are for two pipe steam