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Heat creep in domestic hot water?

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  • Heat creep in domestic hot water?

    I'm working on a bathroom job in this condo building. They have two 120 gallon AO Smith 208 volt (100 amp 3 phase) water heaters , set up with a re-circ line. They have a problem where they get hot water on the cold side of various units sometimes. I know that it MIGHT be a bad check valve for the return line, but have any of you guys dealt with the hot water "creeping" into the cold side? Do I need to add some type of mixing valve?
    Last edited by vette850; 09-01-2009, 08:54 PM.

  • #2
    Re: Heat creep in domestic hot water?

    What kind of pump?

    How many stories?

    Type of faucets and T/S valves?

    Sometimes at washing machines too.

    Many things come to mind.

    J.C.

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    • #3
      Re: Heat creep in domestic hot water?

      B&G recirc pump, 6 stories, all faucets are either taken out or definitely off, washing machines are all disconnected....and it's still occurring.

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      • #4
        Re: Heat creep in domestic hot water?

        All stops under faucets are off?

        T/S valves? What type?

        Thinking....

        J.C.

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        • #5
          Re: Heat creep in domestic hot water?

          shower valves are usually a good bet. a bad check is also a possibility, but i'd be more inclined to blame a valve. pull some trim plates off and see if their are isolation stops on the valve
          No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

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          • #6
            Re: Heat creep in domestic hot water?

            The single handle kitchen faucets are still connected to the stops which are on....I believe they are either Moens or Deltas(They are currently covered by tarps, so I'm not sure. But the amount of hot water coming out of the cold makes me believe that it's not the faucets causing it.

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            • #7
              Re: Heat creep in domestic hot water?

              unplug the recirc for a while, if it's just heat creep it'll still do it.
              No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

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              • #8
                Re: Heat creep in domestic hot water?

                Moens can have this to happen. Sometimes replacing cartridges won't help. Might have to change the fixture.

                The amount can be quite a bit. Lots of pipes with lots of room for tempered water to move.

                J.C.

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                • #9
                  Re: Heat creep in domestic hot water?

                  PRV the recirc HW line to a pressure slightly below city water pressure (CW pressure).

                  Could recirc pump be pushing HW water through all of the single handle fixtures?


                  Pressure balancing cartridges would bleed through I bet....

                  hmmmm

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                  • #10
                    Re: Heat creep in domestic hot water?

                    I am in the process of replacing all of the shower valves with Moen posi-temps, the old ones are 1225 b's. I'll see what happens but the thing that leads me to something in the mechanical room is the the 2" cold water main passing near the heaters was warm to the touch.

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                    • #11
                      Re: Heat creep in domestic hot water?

                      moen faucets with the brass cartridge can and will cross over. it's the diagonal o-ring that's bad. this wall cause mixing of hot and cold , buy not a dripping faucet.

                      the plastic magnum cartridge is a drop in replacement and will solve that.

                      easy to feel flex lines under sinks for the hot one when all is off.

                      tub and shower is harder to isolate. if the hot and cold water mains are exposed in the garage below, an infrared non contact thermometer is the tool of choice to take readings and home in on the riser.

                      had one yesterday that took 10 minutes to locate in a 3 story 12 unit building.

                      3rd floor master shower keeps his hot and cold 2 handle shower on and shuts off the hand held shower so the temperature adjustment stays the same.

                      this particular shower hand held is a medical design that shuts 100% and not like the normal ones that throttle down.

                      owner says he's done it for years

                      i guess he finally pissed off his neighbors and i busted him

                      rick.
                      phoebe it is

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                      • #12
                        Re: Heat creep in domestic hot water?

                        Another place I have seen this happen is when the mop sink if there is one has had a hose and valve of some sort added to the spout, the janitors sometimes tend to leave the hot and cold both on and operate from the end of their hose or Y-type attatchment. The hot can then cross into the cold lines.

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                        • #13
                          Re: Heat creep in domestic hot water?

                          Is there a janitors closet on one of the floors in the bldng? If so check to see soap machines for mop buckets are hooked up to the faucet withe a shut off under the spout,the faucet might be on both the hot and cold side transfering hot to cold line.

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                          • #14
                            Re: Heat creep in domestic hot water?

                            There is an old thread on here ( 2 - 3 years ago ) with the same problem in a house , I seem to remember that they even tried adding a Watts dual check to the cold line and it still didn't stop it , not sure if they ever solved the problem .
                            Steve in the trade since 73 doing new residential/Commercial work

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