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DHW indirect tank question

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MBean0302
MBean0302 Member Posts: 6
in Plumbing
Have a new customer with a indirect storage tank and a complaint of insufficient hot water capacity. Whole system is fairly new and customer doesn't want to pay for a larger tank. In this particular application, customer already has a timed recirculation pump w/ crossover valve at furthest fixture. No dedicated recirc line.

I would like to propose adding a mixing valve tied into cold water line along with raising the temp on the boiler for the DHW priority to get a little more capacity.

My question is, with the crossover valve installed, when the recirc pump is running, would it cause the cold water to be heated enough that the mixing valve would feed a higher temp hot water than is set for?

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  • Larry Weingarten
    Larry Weingarten Member Posts: 3,293
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    Hello, My understanding of crossover valves is they are thermostatically controlled, so when hot water arrives to the valve, it closes down, preventing hot from getting into the cold side. I'd still look at the valve that's installed and see if it is as I described.
    Another thing to consider before making changes, is the possibility of a cross connection. Have you had opportunity to check for that? Also, I'm wondering what your client's use is that it drains the tank. Is there an eight gpm showerhead? :D

    Yours, Larry
    MBean0302
  • MBean0302
    MBean0302 Member Posts: 6
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    I think the issue is 3 bathrooms with a wife and two teenage girls lol

    I believe you are correct about the crossovers being thermostatic controlled... I'll have to get the actual cut out temp from mfg but I would assume 100-120 degrees would be close. I didn't really think of that. I just got all this info yesterday and hadn't had a chance to call mfg until tomorrow. It's a Watts system i'm not familiar with. Now that i'm thinking of it, I wonder how the pump knows when all the crossovers are closed? I noted it had a timer but that's just a time where the pump is allowed to operate, kind of like a defrost timer... I'll definitely have to do my research on this particular pump.

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