I have the AutoPilot Total Control system which lets you set an ORP level which the system will then maintain.
I am trying to figure out what the ideal ORP level to shoot for should be. Various sources suggest an ORP level of 650-750. The Total Control system defaults to a level of 650. Other sources suggest a chlorine level of 3-5, which on my pool/sensor seems to correspond to an ORP level of about 590. Now I know that ORP readings can be affected by the CYA level and most of the people who suggest an ORP of 650 seem to ignore CYA or assume that it is zero.
The other thing I have noticed, which seems to complicate things greatly, is that any external addition of chemicals can send the ORP reading off wildly in one direction or the other for hours, or in one case days, at a time. Since I just opened the pool and was adjusting things for most of a week the ORP readings were varying wildly. It seemed like the ORP sensor was broken for a while. Plus, I have no idea if my sensor is properly calibrated, or what standard I would use to calibrate it against.
Sadly the Total Control manual says nothing on this subject.
Poolsean? Anyone else?