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Strange near boiler piping here......

EricEric Member Posts: 261
Hello all.

Can someone take a look at these pictures of a customer's home we were at recently. They called us there for a Rinnai tankless estimate. Currently they are getting HW from the tankless coil in the 1-pipe steam boiler. Customer thinks the boiler is from the 60's.

They have zero main vents in the basement and have some rooms that never get warm. The supply leaving the boiler is 3" and it splits to 2- 2" mains which wrap around opposite ends of the home, then join back at the insulated vertical line in the picture. 

The first 15' or so of the supply lines are pitched back to the boiler and each feed 2-radiators along their run, so I assume the tees on either side of the 3" main are to receive condensate and keep it from raining down the 3".  The rest of the main changes direction and condensate flows with steam. Each main is about 60' to 70' total length.

How is this working that the supply and returns are joined above the water line?

Steam must be traveling up the return as well as I can't see anything to stop it. 

I can understand the 2-supply tees draining condensate but they should be brought down to a wet return, not above the water line?

The mains are being vented thru the radiator vents which must be killing his fuel economy.

I think this one will be a candidate for a replacement.

Oh yes, the tankless coil is shot as well, so I have some figuring to do for these people.


  • SteamheadSteamhead Member Posts: 11,328
    edited May 2013
    Good eye!

    you definitely have a situation where steam can short-circuit thru those drips and into the various dry returns. The explanation is that the original boiler had a much higher waterline, which kept the tees and wyes under water so the steam couldn't get past.

    You'll have to repipe all of them below the waterline, after first properly removing the asbestos.

    While I am a fan of conversion burners, I wouldn't have used that old-school Economite in that type of boiler. It's not a flame-retention burner so you're probably getting a lot of impingement. Have you done a combustion test? I bet the CO levels are rather high.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • EricEric Member Posts: 261
    edited May 2013
    I didn't realize....

    I didn't realize what I was walking into, had I known I would have brought my combustion analyzer. I try and keep it out of the truck unless it's needed to keep it safe.

    That makes total sense that the water level must have been higher on the original boiler.

     The boiler did fire for hot water while I had the customer run the shower and test the coil, it did fire off pretty loud and he complained how loud it is upstairs while the boiler is running.

    Thanks for the input
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