Quote:
Originally posted by Since87
I did a bit of googling. Johnson Controls has "proportional control" electric ball valves. Didn't find much technical detail though. Hard to say how easy it would be to control such. These valves may not be adequately stable when set between full open and full closed. Also, backlash could make the control system a bit tricky. Possibly worth considering though.
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No valve is stable across its entire range of % open, but yeah, I'd expect a ball valve to be more difficult to control than a linear or proportional valve.
A P-only controller has the downside of being slow to act and having an offset, so usually it's impossible to get a flowrate to be fixed on a single value - it will hover near the value, but almost never land directly on it. PI controllers are much better with accuracy, though more difficult to tune.
It would be important to know what sort of flowmeter is used with the controller and valve. If it's not terribly accurate, P-only would be adequate, as anything more advanced would still be operating off incorrect flow signals.
Alchemy