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  • Tankless Hotwater Heaters

    Is it possible to install a hot water recirc system on a household hot water system with a tankless hot water heater?
    JC

  • #2
    yes it is. although you will need a small storage tank to circulate the return water into. the tankless heater require a min of 1/2 gallon per minute to kick on. unless you have a storage tank the heater will be kicking on constantly as the temperature drops on the return line. a storage tank will allow for more capacity prior to the heater kicking on. you will also need an aquastat and pump, check valves. there are some good drawings on the different web sites.
    try noritz, tagagi, bosch, rheem.

    i'm not a big fan of residential tankless heaters. especially if you need a return line. only advantage of tankless is small size and large capicity potential. not a money saver, or gas saver. not an easy change out from tank to tankless. you need a new cat. 3 stanless vent flue through the roof , or an outdoor heater installation with outdoor kit. or a direct vent heater and kit. you also need a larger gas line to feed the higher btu heater. tank heater approx. 40,000 btu. tankless heater approx. 199,000 btu.

    this topic has come up before and there was a lot of debate over it. search for old post on tankless.

    rick.
    phoebe it is

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    • #3
      Thanks Rick,

      I installed a Bosch tankless when I moved into this house. A vent stack was available and I had the utility upgrade the 250,000btu/hr gas system to 400,000but/hr to handle the increased load.

      My decision was based on fuel efficiency, reduced space, and having teenagers who can run any normal hotwater tank cold in the morning!

      The recirc system would be handy but appears to be a tricky arrangement. Luckily most of my hotwater loads are almost directly above my heater, so the hot water supply lines are short giving a short warm up time. I manifolded the hot water line out of the heater in order to provide a good flow and not upsize to the 3/4 inch line which would increase the warmup time.

      JC
      JC

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      • #4
        don't get tank'd

        STIEBEL ELEKTRON + silver shark

        seems like you are looking for a small package boiler, how many mbtu??

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        • #5
          The unit is for residential service and has a max fuel flow is 175,000btu/hr which is 6.5usgpm at 45degF delta T. In Canada in winter we can expect a 75degF delta T and the until will still supply 3.5usgpm which is more than enough for the shower.
          JC

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          • #6
            Originally posted by Ski John View Post
            Thanks Rick,

            I installed a Bosch tankless when I moved into this house. A vent stack was available and I had the utility upgrade the 250,000btu/hr gas system to 400,000but/hr to handle the increased load.

            JC
            out here that vent stack would have to be a category 3 stainless steel vent. the flue gas temperature is very high and the condensation produced will rot out a normal type b double wall vent.

            rick.
            phoebe it is

            Comment


            • #7
              Originally posted by Ski John View Post
              Is it possible to install a hot water recirc system on a household hot water system with a tankless hot water heater?
              John,

              Understand this is like saying I have an electric car would it be possible to install a backup V-10 in it?

              Mark
              "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

              I never lost a cent on the jobs I didn't get!

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