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  1. #1
    Join Date
    Sep 2014
    Location
    Los Angeles
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    Help with a pneumatic hot water valve

    Hello, I wanted to see if this pneumatic valve is repairable or if it should be replaced. When I set the stat to 60 degrees I get 22 psi pushing down the hot water valve spring. When I set the stat to 80 degrees I get 0 psi to the hot water valve. The stat originally set at 70 gets 11 psi. The back story to this is this room was overheating earlier in the year so my supervisor shut of the coil valves and never came back to troubleshoot. This is the valve https://www.grainger.com/product/JOH...e-Valve-41P936 and this is the actuator https://www.grainger.com/product/JOH...-13-psi-41P643 Ive never used a manometer on the high and low ports but I added that info as well. With the spring fully pushed down I am getting 161 degrees flowing through the coil outlet but on a different vav box with a Schneider electric valve getting 22 psi in cooling mode I noticed the flow is restricted with the coil outlet reading 126 degrees and when full heating it immediately reads 177 degrees with the water flowing.
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  2. #2
    Join Date
    Nov 2011
    Location
    East Side
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    5,045
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    Use an infrared thermometer to calibrate the stat. Shoot the stat at the diaphragm plate to get temp. The stat should break (hiss) at the temperature of your thermometer reading.

    IF the stat is 70*, when the thumbwheel reads 70*, it should hiss. If it doesn’t adjust the small set screw until it does.

  3. #3
    Join Date
    Sep 2014
    Location
    Los Angeles
    Posts
    33
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    Thread Starter
    I'll definitely calibrate it soon, just wondering what to do if that stat is calibrated and set at full cooling mode yet it is still blasting out heat?

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    17,078
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    20# is too much
    5 to 15 is operating pressure
    Air to close.

    Have you cleaned the seats?

  5. #5
    Join Date
    May 2018
    Posts
    14
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    1. Max pressure for the actuator is 25#, 22# is too much. I wouldn't be surprised if it's seen over 25# and messed up the diaphragm, piston or valve

    2. Your thermostat needs to be calibrated

    3. Remove the head to see if your coil temp drops to normal so you can eliminate whether the problem lies with the head or the valve

    4. You can replace the diaphragm on the head but it's only $40 cheaper than a new actuator. I'm not sure if the valve can be rebuilt but it wouldn't be worth rebuilding in my opinion. By the time you rebuild it you could've put in a new valve in half the time

  6. #6
    Join Date
    Nov 2011
    Location
    East Side
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    What is the JCI SDV? Is that the vav box?

  7. #7
    Join Date
    Aug 2000
    Location
    Under my tree
    Posts
    5,119
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    You have the wrong valve in this application. Look at the graingers pic. Stem down opens, stem up closes. JMHO
    To much work with too little time!!!!

  8. #8
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    243
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    If thats the case get a RA Stat

    Sent from my SM-G920R4 using Tapatalk

  9. #9
    Join Date
    Nov 2011
    Location
    East Side
    Posts
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    That’s a 3 way valve. So it could be a mixing or a bypass valve. More likely a bypass, so it would be to the coil or not to the coil. Direct acting would push the stem down, which would be to the coil.

  10. #10
    Join Date
    Nov 2016
    Location
    NYC
    Posts
    2,080
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    Just replace the valve... Do your company and the customer a favor.

    This supports chapter 3 in my book "Legends of the Trade"
    HVAC Magician @ UA Local 638

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