Mixing valve
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Thread: Mixing valve

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  1. #1
    Join Date
    Aug 2004
    Location
    Massachusetts
    Posts
    39
    I recently received a call from a customer complaining of having no mixing valve on her tankless coil. What I found was two boilers in this home with one having a mixing valve and the other piped into that same mixing valve. Someone apparently removed the valve on the second boiler because the stubs were still there. I installed a new mixing valve but wasn't getting any hot water out of it. I figured out why they did this. The tankless needed to be replaced but they took the cheap way out and tied into the other tankless. The tankless coil is too far gone to steam and the customer doesn't have the money to change it out right now. This service call brings me to my question, I've seen this several times and don't know why it does this. When I check the water temp it starts out by spiking up to 150-160 then drops down to what I set it at, usually 125 degrees. Can anyone tell me why it does this and how could it be prevented? Thanks!

  2. #2

    mixing valve

    I suspect the valve needs to see some flow before it can regulate itself.

  3. #3
    Join Date
    Sep 2004
    Posts
    654
    I second that, it responds to flow to regulate.

    The mixing element is likely no good anyways, they seem to last about a year before sediment attacks them.


  4. #4
    Join Date
    Mar 2001
    Posts
    365

    Mixing valves

    A mixing valve needs a heat trap installed before the hot inlet to prevent premature failure. Read the paper work in the box .

  5. #5
    Join Date
    Jan 2005
    Location
    Massachusetts
    Posts
    514
    Most codes require ten to twelve inches of trap.

  6. #6
    Join Date
    Dec 2004
    Posts
    17
    I'm having an issue with a newly installed mixing valve. I'm not sure they put piped it for a "heat trap". So I can be a little more informed when I call my installer, could someone define what a heat trap is? Thanks.

  7. #7
    Join Date
    Mar 2001
    Posts
    365

    Heat Trap

    It's a pipe configuation that traps migration of heat.......

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