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HTP Phoenix Light Duty 60 gallon: adding hydronic heating

We purchased a Phoenix Light Duty 60 gal water heater (it’s a Westinghouse-branded unit). Our intention is to add some hydronic heating via a re-circulation line connected to the auxiliary return: two radiators (~1400 BTU/410W) and two towel warmers (~1,300 BTU/370W). We are trying to figure out if the Phoenix can handle this set-up. We are in northern California (SF), so the climate is pretty mild. The main heating of the house is a gas furnace; the radiators would be placed in the in-law unit that currently doesn’t have any heating.

Our plumber has never seen or installed a Phoenix unit; he is also not very experienced with hydronic heating since this is quite uncommon in California.

Any comments or suggestions? Is this feasible?


  • Jamie Hall
    Jamie Hall Member Posts: 23,442
    What is the total wattage of that Phoenix unit? It might be that it us very close to the hydronic load you are putting on it, in which case you are assuredly not treating it as a light duty unit, and how long it will last is anyone's guess. Other than that, it will probably work. You will need a pump, of course, and it will have to be a rather low flow pump.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,076
    Is this the 76,000 BTUH condensing water heater? I&O manual shows air handler piped near tank. Text mentions aux connections may be used for plate heat exchangers also.

    You would need a bronze or SS pump between tank and HEX.
    Then another pump for heating water circuit and all accessories that go with hydronic heating. The heating water must be isolated from your DHW hot water to avoid the serious nasties that come from stagnate heating water.
  • SanFranTH
    SanFranTH Member Posts: 17
    Yes, it's the 76,000 BTUH condensing water heater, see attached brochure.

    Good point regarding the stagnate heating water; I didn't consider this aspect. We naively assumed the heating water from the radiators can be returned back into the DHW tank.

    Any recommendation on the bronze/SS pump?

    I found these Plate Heat Exchangers:



    JUGHNE Member Posts: 11,076
    The HTP commercial grade Phoenix piping diagrams show the diagram for a flat plate heat exchanger. The Light duty shows only an air handler coil. Why not showing an HEX I don't know.

    Try locating someone in your area under the "Find a Contractor" site on the main wall.
  • Rich_49
    Rich_49 Member Posts: 2,766
    IMO it would be fine for that application with the HX and circs . You could use a control that exercises the circ for 3 minutes daily to avoid the stagnation issue but who wants 3 minutes of hot water through some rads once a day . That was sarcasm .

    Look at Warmsource from Warmboard . That is in fact a Phoenix light duty with Terry's hydronic module on top . I believe this is the reason why HTP does not show it being used for Hydronic heating with the exception of the AHU application .

    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833