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Indirect Piping...

Larry_10
Larry_10 Member Posts: 127
in THE MAIN WALL
Is it a good practice for an indirect DHW tank to be installed with check valves to prevent thermal siphoning? Should they be both on the domestic and boiler piping?

Comments

  • Weezbo
    Weezbo Member Posts: 6,231
    i think so,especially with a domestic re circ line.....

    tapped into the cold water side inlet with an st 12 or the like to take up any expansion.
  • Ron Schroeder_3
    Ron Schroeder_3 Member Posts: 254


    I always use flow checks on both supply and return of the boiler side piping as close as practical to the tank and insulate those lines well. It's especially helpfull in the summer with a cold start boiler.

    I also run the tanks aquastat at at least 150 degrees with a 20 degree differential and a tempering valve on the output. The high temp reduces the chance of bacteria and the wide diff. reduces the boiler firing to often less than once a day with a well insulated tank.

    Ron
  • jim sokolovic
    jim sokolovic Member Posts: 439
    A thermal trap can be created...

    on the domestic hot water outlet of the tank (after the T+P relief valve, if installed in the same tapping), with a short downward drop, 2 elbows, then back up again. This reduces heat migration up the hot water pipe. Some people don't like to wait for the pipes to heat up before they can get hot water - they want it right away, and don't care if some BTUH's are wasted - so the trap is not recommended for those jobs. Guess you have to ask the homeowner what's important to them?
  • hr
    hr Member Posts: 6,106
    atta boy, Ron

    I agree check pump and or a ZV or flow check on the return. Indirects have a habit of overheating from fickle ghost flows. That large tank of cooler (than boiler) water likes to steal away warmth from the hotter boiler water. Don't let it get away with that.

    P/S piping, alone, will not do it. The new versions of check pumps on the market make this easier than ever :)

    hot rod

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