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Recirc pump with mixing valve

I am replacing my ancient tank water heater with a new high efficiency tank heater. I have an existing recirculating loupe in place with a timer driven recirculation pump. I wish to add a mixing valve to temper the water delivered to the fixtures (Taco 5003-C3) and cannot devise or find a plumbing diagram I think will work. How is this accomplished with the low flow of the recirc pump plus no water being removed from the system, allowing cold tempering water in?

Comments

  • WeezboWeezbo Member Posts: 6,232
    edited December 2013
    howdy,

    bring the mixed cooler Hot back from the house to the cold side of the tank with a couple checks against flow ,

    that allows the water choices to feed the tank and or mixer and not allow the cold water to find and easy path back through the tempered water . or the tempered water some errant path though the cold in the event that a hose bib had a take off ahead of the tank near by.

    Hope that helps ,

    there are a lot of similar pictures of this exact lash up that you would like here on the site ..

    you can search through threads using single words ..and it has pictures and explanations and the like in the answers that were given .



    Weezbo



    there are quite a few different systems for recirc these days ,

    if you have a name of the manufacturer or a pic of the recirculator it is easier to describe sometimes .
  • RusselRussel Member Posts: 4
    Recirc pump with mixing valve

    Thanks for the comments. My concern is not cold water intrusion but absence of cool water to add to the hot water loupe. If I return the water from the tempered loupe into the tank, the only source for replacement water supply to the mixer valve and tempered loupe would be hot water from the tank. Also thee are no cold water taps anywhere along the loupe or nearby in the cold supply. Perhaps I am misunderstanding your comments. If my system is still unclear, I could post a schematic.
  • WeezboWeezbo Member Posts: 6,232
    edited December 2013
    that is what it does ,...

    the hot water at a tapat a sink , we can call this tempered water , has a path back to the water heaters cold water feed line, into the tank through its hot ,to the cold side of the Tank you have, to the tempering valve , out into the supply back to the hot water tap we started with at the sink..

    one big loop ..



    that costs more energy , other way is basically the incoming cold is checked away from the water heater , that way it gathers heat thru standing as it were in the room ,..

    that makes it warmer , then when there is a call for hot water ,...the water is warmer than the incoming water from the street , that reduces the time it takes to mix back up to the tempered water output in the anti scald valve ..which would then be living on the water heater rather than the Indirect tank.

    only when you used tempered water , would the water move from the indirect into the waterheater and out the tap. otherwise it does not see the recirc because of the check valve ...
  • RusselRussel Member Posts: 4
    Recirc pump with mixing valve

    Thanks for the time. Will search for a schematic you mention
  • ZmanZman Member Posts: 5,614
    Mixing

    You are correct to be thinking this through.

    The key is to give the cold side access to the returning water.

    This drawing does a good job. It is amazing how many of these are piped wrong.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RusselRussel Member Posts: 4
    Recirc pump with mixing valve

    This is what I had in mind but still see some potential caveats. If pump flow is too low, the mixing valve will not function (per specs) but if too high, the return water temp will be too high and mixing valve will not function well (per spec). I understand that the balancing valves will help to mitigate the high temp return water by bringing in some water from the cold water inlet to the tank but in reality, the only cold water is in the short segment before the pipe enters the tank and most of the "cool" make up water will come from the bottom of the tank. Not sure how much cooler the bottom is than the top due to stratification but if this design works, it must be significant. I was also thinking of placing a high temp limit on the return water to shut down the pump when it is at design temp, but only if this design doesn't work out well. Not sure I want to use the Taco smart pump because our usage is so varied and random. I have a reliable pump n the loupe now I will likely reinstall. Anyway, looks like I will give this schematic a go and tweak as needed with balancing valves. Sorry about the long winded post and thanks to both of you for your good advice.

    I am also installing a Taco heat exchanger with variable speed pumps for my hydronic heating but that's for a little later.
  • ZmanZman Member Posts: 5,614
    Recirc

    That setup works pretty well in the real world.

    If you get into really high flow rates like you see in commercial work, I high/low valve setup may be needed.

    I would not run the recirc 24/7 regardless.

    It uses energy and will wear out the pipes.

    An aquastat on the return is a good call.

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SWEISWEI Member Posts: 7,356
    Taco 563-2

    should work for shutting off the pump.  Even better if you pair that with a motion sensor or some other kind of demand switch.
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