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Using a boiler DHW coil as a HX for a hydronic loop?

Settling in on a 19HE as a replacement boiler and in my size range I can order with up to two DHW coils. Can those be used as a HX for a hydronic loop ? That would solve dissolved air entry into the loop and associated corrosion issues.
In this case I'd just pipe it like a conventional HW loop? (compression tank etc?) but with a bypass to adjust temperature?
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.


  • mattmia2
    mattmia2 Member Posts: 9,662
    Yes. Aquastat on the boiler to heat it for the hot water loop but not cause it to steam on a heat call. Needs a relief valve.

    Don't need a bypass in most cases, what do you think you need it for?
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    This article discusses various options for running a hot water loop off a steam boiler. The Systems Help Center has some other articles you might find helpful.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
    Erin Holohan Haskelldelcrossv
  • Derheatmeister
    Derheatmeister Member Posts: 1,544
    We installed a reverse indirect on a system without o2 barrier to mediate between a Viessmann and PB tubing..Works great.