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boiler sizing

switchmaster
switchmaster Member Posts: 1
in Strictly Steam
I have bid against another contractor for a steam heat boiler replacement, the customer called me back questioning the boiler size because I bid a Weil McClain EG-55 and he had a EG-75. I pulled the BTU requirements from the book Every Darn Radiator and came up with 146803 BTU required. I called Weil McClain and confirmed that I was correct after double checking my numbers. They gave me this site and said to double check.

Also what could be the problems of the oversize boiler on a old steam system? My first time with this.

Thank you,

Steve Olson

Comments

  • Rod
    Rod Posts: 2,067
    Boiler Sizing

    Hi Steve-   Welcome to the Steam board.    First of all I must qualify that I’m a homeowner and not a steam pro.  There are lot of really experienced steam pros who are members of this website and I'm sure will be glad to answer any questions you have though don’t be surprised if it takes a day or so to get an answer as things are rather slow on the board at  this time of the year so some of them don't come on that often.



    The new boiler size should be closely matched to the total EDR of the radiators with a “pickup factor” of 1.33 added.   If the boiler is oversized, it will short cycle.   An EG75 is 229 ft of steam larger than an EG 55.  If your measurements are correct that would make the EG75 way oversized.  Did the other contractor size it to the old boiler?   It's pretty common for old boilers to be way oversized as a lot of installers didn't /don't know how to properly size a boiler.so if one replaces it with the same size boiler.  I’ve attached sheet below that helps calculate this out as you might want to use it a check on your figures.



    Here’s a link that may be of help to you: http://www.heatinghelp.com/article/323/Boilers/234/Replacing-Your-Old-Steam-Boiler



    Piping-

    The near boiler piping is especially important so be sure you closely follow the recommended pipe sizes, heights and configurations shown in the factory installation manual. The height of the riser pies coming out of the boiler is especially important.  Here’s a good video on the subject:

    http://www.heatinghelp.com/article/107/Steam-Heating/118/Steam-boiler-near-boiler-piping



    If you don't already have them there are some really good steam books available in the Shop section of this website.

    Don't hesitate to ask questions.  We'll do our best to answer them.

    - Rod
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