Harry Belafonte sure had it dialed in back in the day, didn’t he?
“Man Smart, Woman Smarter,” sage advice for men of any age…
Last time out (click here) we discussed the importance of thinking for today’s hydronics professional, and the dangerous and downright insulting advice that any product – even so-called “smart” pumps – can “do the thinking for you,” “take the thinking out of it,” or even worse: “take the guesswork out of it.”
Gang, we all know there’s only one way to take the guesswork out of hydronics…
Do the math!
“Smart” pumps? Please – they’re not that smart. Here are two examples of how “smart” pumps behave in a thermostatic radiator valve (TRV) system:
Delta-T: The external info a Delta-T residential circulator uses to vary its speed is the systemwide Delta-T, meaning the temperature difference between the water leaving the boiler and the water coming back from the system. The pump is set for a default 20* Delta-T (adjustable from 5 to 50), and will go faster or slow depending on how many BTU’s are being taken out of the system at any given point in time.
In a panel radiator system, when a TRV closes (meaning there’s enough heat in the room), the Delta-T across that radiator will actually increase. This would be a message for the circulator to speed up, even though the radiator is fine.
Kinda goofy, right?
But common sense tells us there’s more than one radiator in a system, and more than one TRV. While one is closing, another may beopening, and another may be holding steady. There’s no way for a Delta-T pump to know what each radiator needs. So what does it do?
It varies its speed based on the boiler supply temperature and the common return temperature. That’s all it knows.
Delta-P: Delta-P varies its speed based on changing pressure differentials in a system, and was designed for TRV applications. But even here Delta-P isn’t that smart.
The “trigger” that tells a Delta-P circulator to speed up or slow down (even with so-called “AutoAdapt) is resistance against the impeller. When there’s enough heat in a room a TRV will start to close, placing more resistance against the impeller. The circulator senses that, and slows down.
So far, so good, right?
But again, common sense tells us there’s more than one radiator in a system, and more than one TRV. While one is closing, another may be opening, and other may be holding steady. What’s a Delta-P circulator to do?
Same thing as Delta-T: react to the overall system-wide changes in pressure differential.
It varies its speed based on overall system pressure differential. That’s all it knows.
Heating Man Smart, but “smart” pumps definitely not smarter!
And try keeping this Belafonte classic from banging around your head the rest of the day…
One of the smoothest voices ever…
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