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  1. #1
    Join Date
    Oct 2011
    Location
    Austin, TX
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    ambient temperature affect on closed loop water line?

    Hey guys, I am installing my first glycol chiller for a local brewery here and have a question about leak testing the closed loop. I'm using 4" pre insulated sched 80 pvc for the loop. I installed bleeder valves at the highest point on both return and supply lines and made a manifold with a ball valve and pressure gauge. I have to pressurize the lines to 2 times of what the chiller pump will push the glycol, in this case it will not get any higher than 20 psi. I hooked a water hose to the manifold and filled the system up until water came out of the bleeder valves, shut them off, and then shut my manifold ball valve off when the pressure got to 40 psi. Went to lunch and came back and pressure was the same. Returned this morning and found that the pressure had dropped about 3-4 psi.
    I have looked everywhere and there are no indications of leaks, ( water on the floor) and none of my pipe joints are covered yet so a leak would be easy to locate. so my question is, is it possible that the city water ( usually around 60-70 degrees) cooled off a little bit over night ( it was in the 40s) and that's why my pressure dropped 4 psi? Any advice would be much appreciated. Thanks,

  2. #2
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Absolutely. If you didn't get all of the air out, that will cause issues as well. But that doesn't mean the pressure drop was completely due to ambient cooling or that 3-4 psi is acceptable. It depends on your system volume and fluid concentration (if you used something other than just water). Think about a very large system (millions of gallons)...a very small change in temperature (assuming that it changed evenly), might create a very large volume change. A very small system (a few gallons) might not create any field measurable change in volume.
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  3. #3
    Join Date
    Oct 2011
    Location
    Austin, TX
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    Thread Starter
    Ok, I would guess that these pipes are holding close to about 600 gallons of water. All the air should be out of the system and it is just water. The building that they are in is a warehouse and there is no HVAC running so it did get chilly in there overnight. After your comments I think that the ambient temp is what caused the minor pressure drop. Thanks for your input!!!

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