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Question about boiler water in indirect water heater coil.

RxRoy Member Posts: 22
Hi Everyone,

I have a Lochinvar Knight WHN 055 modcon boiler. I would like to use part of its capacity to heat my DHW with a Lochinvar Squire indirect water heater. (I'm not worried about keeping up with heating load, I believe it is oversized.) In the install manual of the Squire, it states this:

"Single-wall heat exchangers are permitted if they satisfy all of
the following requirements --
1. The heat transfer medium is potable water or contains only
substances which are recognized as safe by the U.S. Food
and Drug Administration.
2. The pressure of the heat transfer medium is maintained less
than the normal minimum operating pressure of the
potable water system.
3. The equipment is permanently labeled to indicate that
only additives recognized as safe by the FDA shall be used
in the heat transfer medium."

I have added Rhomar 922 to the boiler water.

Does anyone know if Rhomar 922 is "safe by the US Food and Drug Administration"?
I looked at the safety data sheet, but it didn't specifically list that anywhere.

For what its worth, the boiler circuit of the indirect runs at ~13 PSI. My house (well water) runs at 40-60 PSI.

Thanks for your help!


    HVACNUT Member Posts: 5,855
    Your fine. CYA on their part.

    1- Your using potable water for your DHW needs. (Unless you have that special well water that ignites.)
    2- Vessel pressure is greater than the HX pressure.
    And C- This is your home? Put a skull and crossbones sticker on if you want. It's still potable water.

    BTW, you can program the boiler for DHW priority, as long as it's piped correctly.
  • RxRoy
    RxRoy Member Posts: 22
    Excellent! The CYA part hadn't occurred to me, but makes sense. Thanks!