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boiler sizing, connected load, and pipes.

dobro23 Member Posts: 71
edited February 2019 in Strictly Steam
maybe this is easier than i think and i am just over thinking things but my company is bidding on replacing a steam boiler. several of the radiators from the original system have been removed and several of the existing radiation is in the form or fully recessed cast iron convectors. after seeing the job today for the first time i have a few questions. 1. without knowing the brand of the convectors, the closest thing i could find in the EDR book were american radiator co. the width of my element is only 3-3/4" though. its basically 2 " passes". the enclosure looks different from the american radiator ones though in that the louvers are vertical instead of horizontal. so, having a hard time pinpointing what these are is giving me a hard time figuring the EDR into my load. 2. a few rooms have had their radiation removed altogether. can i do a heat load of the room and divide the total BTUs by 240 to get the total sq ft of radiation needed so i know how many EDR the necessary radiator needs? 3. the original boiler which is in pieces way back in the corner of the cellar was huge. maybe an old crane with a 4" supply tapping or 2. hard to tell. there are 2 mains. both start off as 2-1/2" and then reduce to 2" after about a third of the length. the total length of each main is near 50' my intent is to create a dropped header to supply both 2-1/2" mains. 2" risers will supply the header from the boiler. and the header will most likely be 3" or 4". not sure that i know the proper equations to calculate header size. the current boiler is a weil mcclain 566. not running. the supply leaves the boiler as 2-1/2" into a 2-1/2" header. this supplies the 2-1/2" mains with 2" take offs from the header. i know its not ideal but is it ok or should it really be 2-1/2" ? so far my incomplete EDR calculation is a little under 500 sq ft. not sure if my questions can be answered with the information i gave but let me know. here are some pics.

this is the best pic i have of the convectors with the cover removed. also, is that type of vent setup acceptable or should i opt for a conventional STRAIGHT radiator vent hopefully with a larger capacity?

the reducing 90's are 2 to 2-1/2". it's hard to tell in the pic but the pipe run to the house is 2-1/2" the take off on the header is only 2".


  • BobC
    BobC Member Posts: 5,471
    I see what looks like a heat timer vent on one of those convectors, they can cause problems on convectors because they vent too fast.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Well, it certainly looks like you are in need of a replacement!

    And get those mains insulated and vented please.
    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems