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domestic hot water from boiler

apologies if this has been covered here. I tried searching but may have been using incorrect terminology. Currently we have a coil inside our steam boiler for domestic hot water. It worked well enough in the winter when we were running our steam heat all the time, but now we have added some air-source heat pumps and are not running the steam heat much. We would like to add an indirect water heater. I've seen on-line that one can get a coil installed in a a water tank that uses hot water from the boiler and that this would be much more efficient than firing the boiler every time we needed hot water. I've had 3 HVAC people not that interested and even telling me it could not be done. Where do I find a contractor in the Metrowest Boston area who knows steam boilers and can tell me if I can do this or not? Thanks!


  • Jamie HallJamie Hall Posts: 10,407Member
    Try @New England SteamWorks . Really busy, but one of the very best in the business.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • linderalindera Posts: 20Member
    Thank you Jamie. I have just realized I put this comment under controls instead of domestic hot water. Will try to repost it there.
  • Erin Holohan HaskellErin Holohan Haskell Posts: 1,048Member, Moderator, Administrator
    @lindera - I've moved this post from the Controls category to Domestic Hot Water category.
  • HVACNUTHVACNUT Posts: 2,135Member
    Theres 2 ways to add an indirect water heater with a steam boiler.
    The first is to tap a supply and return on the boiler below the water line.There should even be a piping diagram in the I&O manual.
    If you dont have the manual or it's an older boiler, post the Brand, model boiler and pics of the boiler and connected piping and the steam pros here can guide you a little better.
    The second way is to use the existing tankless coil and pipe it like a 1 zone boiler.
  • linderalindera Posts: 20Member
    Thank you for your help. This is our first winter with heat pumps. So far (even with temps in the teens) we have not had to use the boiler. We are now wondering if it makes sense to keep the boiler just for hot water or whether we should move to some other way of producing hot water.

    Also can someone tell me how to get email notifications when there are new posts to this thread? Thanks!
  • pecmsgpecmsg Posts: 728Member
    Heat pumps are great but you still need a back up source of heat for when they fail.
    As @Jamie Hall said @New England SteamWorks is who you want!
  • HVACNUTHVACNUT Posts: 2,135Member
    Yes keep the boiler. Address the DHW with an indirect.
    You should have a 2 stage thermostat for heat for when it gets cold and wired properly will provide heat from the boiler during the heat pumps defrost cycle.

    As far as email notifications, PM @Erin Holohan Haskell aka "Boss Lady". She can help.
  • Erin Holohan HaskellErin Holohan Haskell Posts: 1,048Member, Moderator, Administrator
    lindera said:

    Also can someone tell me how to get email notifications when there are new posts to this thread? Thanks!

    @lindera - Click on the star at the top of this thread to the right of the "domestic hot water from boiler" heading.

    Here are more tips for using the forum:
  • LeonardLeonard Posts: 828Member
    edited January 2
    Other issue is during power failures a heat pump would need a medium sized generator to keep making heat. Depending on model of gen and pump maybe 6 KW to start the pump motor. While a nat gas steam boiler's controls and gas valve might run off a small computer UPS and car bat (can jumper bat to a car to recharge it)
  • linderalindera Posts: 20Member
    Thanks everyone for your input. I do have a somewhat sentimental attachment to the steam heat, probably because I put some effort into learning a bit about it when we moved in. The house was build in 1950. Is it unusual that a relatively young house like this would have steam heat? No beautiful cast iron radiators, unfortunately. Just convectors with their own "mid-century modern" charm.
    We don't plan to make any serious changes this winter. I do think of keeping the boiler as back up, but it occurs to me that we didn't have a back-up when we just had the boiler. Also, although we are certainly using less oil now that we have heat pumps, we are still using it for generating domestic hot water which is not that efficient.

    The defrost cycles on the heat pumps so far are pretty short (just a few minutes). The house does not cool down to the point where the boiler kicks in.

    Thanks again for the recommendation for New England SteamWorks.

    And thanks Erin for the information on how to know when I have responses.
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