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Zone valves with inderect.

jareedo_2 Member Posts: 10
I have a customer who I installed the plumbing for in her new home, she hired another local hvac contractor to install the heating system ,the system is a Buderus G115 with two air handlers and vaughn top performer inderect w.h. all on Honeywell zone valves. The customer has been in the house since early summer and is NOW complaining about not enough hot water. I went aand checked everything out on my end and it's all O.K. ,what I think is happening is since he has the inderect on a zone valve without priority regardless of how the boiler is sized that when the other zones ( the air handlers ) are calling the DHW can't be satisfied because of the path of least resistance happens to be the air handlers because of the friction loss on the inderect.

What do you guys think?


  • hot_rod
    hot_rod Member Posts: 14,552

    the delta t across the indirect tank when no other zones are calling. That tank, as I recall, has a finned copper coil, fairly small id also, but they can lime up (the fins) very fast with hard water. Easily in 6 month's time especially with hot, hot boiler water passing through the coil.

    Luckily the coil is easily remover to cook it clean. Hercules Sizzle is my prefered "chemical romance."

    Measure that delta tee with a cold indirect. If the supply is 180F and the return 175F, you are constipated. No you personally of course, but the heat exchange.

    Certainly the DHW priority would be a plus, and a simple thing to correct, but if the coil is plugged you maybe out of the heat "mode" for a long, long time.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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