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common returns on 2 boilers

ChipChip Member Posts: 13
I removed a lgb6 from an old frat house and replaced it with 2 boilers. the house had an addition put on in the 60s and they installed zone valves on the two supply pipes. Old side of house has cast radiators, new has fintube convectors. The zone valves did not have a condensate drain on them, so as you guessed it, they trapped water and blew apart within months of being installed. I cut the header out, sized the radiators, and tried to split the front and rear. Now the boiler on the rear is flooding and the front boilers water feeder shows 66 gallons fed in one week. So obviously I have a condensate line crossed somewhere... problem is finding it. House is 10000 sqft atleast. Basement is entirely finished. And all piping covered in asbestos. Is it possible to connect the returns together at the boilers? Or am I asking for boiler water level nightmares if I do?

Thanks! Chip


  • Tim_HodgsonTim_Hodgson Member Posts: 59
    I would guess

    you have a wet return system. If so, I would create a false water line and trap it into a condensate tank with a boiler feed pump. I would install a pump control on each boiler that controls a zone valve and let the end switch of the zone valve bring on a pump relay. Zone valves on the steam pipe are fine if they are dripped. I would install a vacuum breaker on each boiler and a high water float and thermostatic trap to prevent over filling of each boiler.

    Good luck,

    Timothy Hodgson
  • SteamheadSteamhead Member Posts: 10,964
    You might try

    using an infrared camera to find where the pipes are. A boiler-feed pump setup as described previously will work, but introduces more mechanical problems down the road. Stick with gravity return if at all possible. 
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