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    Can two boilers make sense? One for steam, one for hot water? (1 Post)

  • WWood_ WWood_ @ 8:36 AM
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    Can two boilers make sense? One for steam, one for hot water?

    Following up to an earlier post of mine, and after doing more research on commenters' advice, I have decided to keep my existing heating setup of 1 steam zone (single pipe) and 3 hot water baseboard zones rather than convert the steam to hot water baseboard.  I am converting to gas. 

    My question is whether it is better to operate 2 smaller boilers, one steam, one hot water, or a single steam boiler that can also generate HW for the baseboard and the indirect 50 gallon hot water tank.  My current setup was an oil Weil Mclain boiler generating both steam & hot water for heat with a separate propane-fired hot water tank.

    The house is almost 2,300 sq ft.  Insulation probably ok in the newer part of the home (hot water baseboard) and probably light in the old part (steam zone).  Windows all double pane replaced 10yrs ago. 

    The hot water baseboard spans about 90 linear feet and covers about 1,450 sq ft of the house. 

    The steam zone covers the remaining ~800 sq ft and is comprised of the following: 4 radiators of 4-tubes, 20" high spanning 73 sections and 1 radiator of 3-tubes, 26" high spanning 5 sections.  I think I calculated something like 45,000 BTU steam design output.

    Some questions:
    How large of a hot water zone can a steam boiler support with reasonable efficiency?  This is what my current set-up did, I'm just not sure it was the most efficient.
    What are the biggest drawbacks to running 2 boilers?  What are are the biggest benefits?
    Using two boilers, what size would you recommend for each (steam and hot water)
    If I down the road I wanted to add a small heat zone for the basement (say 400 sq ft), would that make any difference to my current day decision?

    Thanks,
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