ORP controller question

[Pescador]

Hey Christy
I don't have the Milwaukee controller I have the Red Sea but it sounds like the same idea. Have you checked it with calibration fluid?
Some tanks run a high ORP without ozone but 450 sounds high. My controller has a set point accuracy of + -10% so it can drift up to 40Mv at 400Mv. Also readings can be different in different parts of your tank or sump so maybe try moving the probe around.
Everyone's tank is different but mine stays between 325-375 with 200mg running steady. It drops to about 225 after a water change.
Also on my Red Sea you can't set the ozone level unless the unit is producing ozone.(the red light is on)

[vanreefer]

sounds like it is working the way it is supposed to ie the ozone generator is only given power when theORP level is below the set point, BUT I agree that you probably need to calibrate the probe as an ORP of 450 without ozone seem improbable... at least in my tank anyway