Weighing two freeze protection setups on the automation panel

Started by Marcus Reed · · 2 replies
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#1
Katy guy so this comes up every winter. Panel lets me do it two ways and I keep flip flopping. Option one, just run the VS pump at low RPM, something like 1200, anytime overnight temps are forecast near freezing, call it 600-700 gpm turnover worth of flow just for insurance. Option two, use the freeze sensor threshold, set it at 36F, panel bumps pump to a mid speed only when the sensor actually trips instead of running all night on a maybe.

Option two is way cheaper on kWh obviously but I've had the sensor lag a degree or two behind actual pipe temp on those clear cold nights with no wind. Option one wastes energy on nights that never got close. Anybody run both long enough to have real numbers, or just picked one and stopped worrying about it.

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#2
No automation panel here, just a plug timer, but if your sensor's already lagging a degree or two I'd just set the trip point at 38 instead of 36 and eat the extra runtime, cheaper than finding out it lagged on the wrong night.
#3
Bumping the trip point to 38 helps some but that's still trusting a single sensor reading on a still clear night, which is exactly when radiational cooling drops pipe temp faster than air temp and fools the sensor worst. In the trade we always backed up a single sensor with a bit of margin built into the logic, not just a higher number. I run the freeze sensor setup here too but I set mine to kick the pump on at 36 AND just let it run low speed anytime forecast overnight low is under maybe 38, belt and suspenders. Costs me a little more kWh than sensor alone but nowhere near what option one runs you all winter, and I've never had a freeze crack a fitting since I went dual trigger. Six years now on the same panel logic.

FN