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Wiring of DHW pump is direct and not through the boiler

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CBRob
CBRob Member Posts: 273
edited November 2019 in Radiant Heating
Some of the houses I care take have a triangle tube boiler, with a spot on the wiring board to hook up your DHW circ pump.
Rather than use this hookup the original install has the DHW circuit pump running 24/7.
It seems like whenever there is a call for central heat and the output temp is in the low hundreds, that I will be cooling down the DHW tank.
Is this much of a big deal? Is it worth correcting the wiring so that it runs through the boiler?

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  • JUGHNE
    JUGHNE Member Posts: 11,062
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    I learned to not do that. I have a tube in shell HEX feeding a large tank. I had the tube pump run constantly as it was a hot boiler install.
    What eventually happened was pin holes develop in the the 3/4" type L hard copper. It was a high head pump (free BTW) and had eroded the copper.
    The controls have since been changed.
  • hot_rod
    hot_rod Member Posts: 22,157
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    You should not be pulling heat from the indirect on a heat call, that should be a different piping circuit, check protected often.

    More and more we see systems going back to 24/7 dhw recirculation for legionella protection concerns. Especially on public and health care facilities.

    Stopping the DHW recirc, by whatever means give the bacteria a chance to linger and grow in the biofilm inside the piping. Constant recirc at the appropriate flow rate, and at temperatures above 140 once a day are some of the best anti-legionella prevention steps.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    CBRob
  • CBRob
    CBRob Member Posts: 273
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    > @hot_rod said:
    > You should not be pulling heat from the indirect on a heat call, that should be a different piping circuit, check protected often.
    >
    > More and more we see systems going back to 24/7 dhw recirculation for legionella protection concerns. Especially on public and health care facilities.
    >
    > Stopping the DHW recirc, by whatever means give the bacteria a chance to linger and grow in the biofilm inside the piping. Constant recirc at the appropriate flow rate, and at temperatures above 140 once a day are some of the best anti-legionella prevention steps.


    There is a whole house dhw recirculation, that's probably helping to prevent the bacteria.

    The pump that's running 247 is pumping the glycol solutions to the indirect tank.

    The dhw has its own supply outlet from the triangle tube boiler and return is tied into the primary loop.

    I think when the boiler is getting the central heat call it is still sending glycol through the indirect water heater.
  • pecmsg
    pecmsg Member Posts: 4,853
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    What temperature water are you sending for heat?
  • CBRob
    CBRob Member Posts: 273
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    It's got an outdoor reset, but on a 30° day it's sending out 110° for radiant heat. The curve would be for temps as negative 10.

    I guess a range of 90° to about 120 130...
  • hot_rod
    hot_rod Member Posts: 22,157
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    ot the manual for the boiler? It should show the correct way to pipe and wire the indirect, generally right to the boiler circuit board.

    Most often the indirect is on a priority, heating calls stop until it recovers. The tank flow from the boiler should stop when the tank reaches setpoint.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Jolly Bodger

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