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replacement steam boiler for a small multi family building

tony_19 Member Posts: 29
hi i am in the process of getting quotes for a replacement boiler.. the boiler that is installed there now is a smith-mills 250-251 7 section producing 1950 square ft of steam..

i have received propsal for replacement , with one as little as 1238 sq.ft of steam and one at 2996 sq. ft and one in the middle at 1800 sq. ft. I calculated the total btu for the building and it came out to 380000 btu. the boilers are all different brands...weil-mclain, burnham and peerless. any recomendations on the brand and also why the disparity on the sizes.

thans for your help


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,510
    sizing a steam boiler

    when you calculated the btu load for the building, was this from the radiator sizing in total? steam boiler size must always be calculated from the total connected radiator load, not the building heat loss. even though you may arrive at a figure which makes the boiler look over-sized, it is not. for a more concise explanation of this, see dan's book, "the lost art of steam heating" available here.

    some options which i consider necessary with a new boiler are:

    vaporstat instead of pressuretrol-you will need one later anyway, why not now? make sure you have a good low pressure guage with it [0-15 ounces,].

    modulating, 2-stage burner, to keep the pressure on the 3-8 ounce mark.

    gravity return-don't spend extra money on a pumped return. my 1,050,000btu peerless is all gravity.

    select the installer first, then a boiler with good distribution in your area.

    finally, are you sure that your present boiler cannot be made to work with new sections? check sizing 1st as described already.--nbc
  • tony_19
    tony_19 Member Posts: 29

    the heat load is from the total radiators in the building
    and yes it is a gravity return.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,510

    you may need to double check those radiator size calcs to be sure. the only time i can think of size variations is when the load falls between the ratings of 2 different boilers. otherwise the calculation is rather straightforward.

    whats wrong with the old boiler?--nbc
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688

    what's wrong with the present boiler? The Mills was one of the best designs ever produced, and is still one of the most efficient made today.


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  • tony_19
    tony_19 Member Posts: 29

    it is corroded between one of the sections at the nipple it is not leaking but who knows when it will go
  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    That means

    it has been leaking at some point. Time to replace it.

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  • Ray111
    Ray111 Member Posts: 1
    Replacing a steam boiler in a Multi Family Building

    Hello I have a  7 unit apt building with 2 store front (appx 10k sqft) and the steam boiler that was heating the entire building has now failed. I am looking for some cost effective ideas on how I should replace my heating system. Should I just replace the steam boiler or put in a different method of heating?  
  • Rod
    Rod Posts: 2,067
    Post your message in "Strictly Steam"

    Hi Ray111- You might want to post your question in the "Strictly Steam" section as you will get more responses. As it is now, your question is buried in an old post so may not be seen.  As was mentioned in the replies  to the original post you need to get a heating tech that really knows steam. (most don't!) You might want to take a look in the "Find a Professional" section at the top of this page. Scroll down past the zip code section to the "States" section and see if there is a steam pro listed local to you. There are some really good steam pros located there.  You might also mention where you are located.

    - Rod
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