B,
In my case, I just shut off the circuit breaker that only powers the cell's transformer. I also "deselect" the IntelliChlor check box in ScreenLogic which prevents any error messages.
You can just unplug the cell from the ET, but I would worry about corrosion on the connector pins. If you do unplug it, make sure the power is off to the cell first.
If your Pump Filter Relay is only being used to turn the cell's transformer on/off. Then you could just unplug the relay from the back of the main board..
Thanks,
Jim R.