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Low Loop Volume – The Slow Death for All Chill Water Plants

Throughout my 20-year tenure in the HVAC industry, ranging from consulting to heavy industrial/commercial for the largest OEM to owning my own business, I have the same conversation at least three times a year. "Sir/Mam, you need to increase loop volume."

A general rule of thumb is that you need to have ten gallons per ton for process cooling. When calculating how much water you have in your system, consider your pipe volume and the volume within all the heat exchangers throughout the loop. Systems with long chill water pipe runs typically will be in the safe zone. It’s the short loops that get into trouble.

So why so much water in your system?

Well, once the chiller is satisfied, or has reached design temperature, it unloads or shuts off. If the chiller can cool the loop quickly and the process water can heat up the loop quickly, you can have it to where it gets very hot then very cold in a matter of minutes. You want an appropriate volume of water so that it takes longer to cool or heat up a larger body of water. Low loop volume causes the compressors and fans to cut on and off, having to overcome their designed break horsepower multiple times in a few hours. This might not be a huge deal for a digital scroll compressor, but for a larger, medium voltage, centrifugal machine it can cause a lot of damage over time. I have seen motor windings literally twisted from too many starts/stops. In some industrial sites, they will leave on large, water-cooled chillers constantly for weeks at a time and the machine loves these types of conditions. Keep in mind, your larger equipment is designed to last 20, 30, 50 years. Hoffman Mechanical Solutions maintains machines in South Carolina and North Carolina that date back to the 1960s! With proper maintenance and running the machines as designed, there is no reason that your larger industrial water-cooled machines can’t outlive you and me.

To conclude, if you have loop volume problems, it is a simple fix that doesn’t come with an insane price tag. We have accomplished this many times over and if this is a problem for you, we are happy to think through it with you and come up with a game plan.


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