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Dry vs Wet Returns, Boiler Efficiency.

I'm replacing my boiler on a 1-pipe, wet return system. Is a dry return more efficient than a wet? Another engineer that I work with claims a dry return delivers the condensate back to the boiler at a much higher temperature, so the boiler doesn't have to waste as much energy to reheat the condensate. (His experiance is with large high pressure commercial steam, I don't know how well this translates to my dinky 120,000 btu low pressure gas boiler)

I notice my wet return does get much cooler closer to the boiler. Would the savings be worth the cost to convert to a dry return? My wet return is a 1 1/4" copper replacement done about 10years ago and I flush it yearly.

Would insulating the wet return help? Just thinking outloud.



  • same pipe with different names for different parts

    high pressure boilers really have nothing in common with low pressure heating boilers.

    steam leaves the boiler through the header, then into the mains, then passes through the take-offs into the radiators, where it condenses into water. as water it flows on down the main, entering the dry returns towards the main vents, and drops down into the wet return, and finally through the Hartford loop into the boiler.

    for efficiency of operation, don't use extra fuel to squeeeeeeze the air out of the system as steam rises with constipated little main vents, use big ones [gorton #2's]. as well you can try to keep the pressure low. my 55 rads fill with steam at 2 ounces, and rarely exceed 8 ounces when the temperature drops.

    buy 2 copies of "the lost art of steam heating" here at the shop, and give one to your engineer friend, and one for for yourself.--NBC
  • pecmsgpecmsg Posts: 288Member

    The engineer should be able to understand it………

    It contains lots of pics.
  • jumperjumper Posts: 1,214Member
    engineer is correct

    Dry return is preferable. Except that wet return provides an allowance against running out of return water to boiler. Probably no danger of that in small house requiring 120 mbtu boiler.
  • Drew2100Drew2100 Posts: 9Member
    Thanks for the input.

    Wasn't quite sure about small residential stuff. So, my take is that while a dry return is more efficient, it's not enough of a payback to go through the expense or re-piping the wet to dry return on such a small system.
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