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converting from electric to natural gas boiler or hot water tank

We had a 7kw pass thru boiler on the wall heating a 1400 foot slab we now have the option to go natural gas. lots of reading on the net and i'm not getting anywhere , should I use a small hot water tank or find a on demand boiler seams most of them a sized 75.000 or bigger and I dont think I need that big of a unit ..


  • mikeapolis
    mikeapolis Member Posts: 46
    Have you had a company out to provide you with proper sizing? What are your venting options with the gas boiler? Will you be changing out your water heater to ng?
  • Jamie Hall
    Jamie Hall Member Posts: 23,302
    Do NOT use an on-demand water heater for a radiant slab. Just don't. Find and use a nice wall hung heating boiler, made for the job. They just aren't the same thing at all.

    Also, as @Matigi said, be sure you get proper sizing. You don't need -- in fact can't use on that size slab -- the full output of a 77K unit. But many gas boilers are modulating, and can be turned down to match what you need (and can also be set up to condense, raising your efficiency).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England