I really like your plug idea. That way ground is disconnected as well. I had a waterer inside my freestall barn. Eventually I would switch the power AND ground off before milking. The cows came into the parlor a lot better with both disconnected. I wish I had thought of the plug idea. It would have been a lot safer preventing power to be on without the ground, but I was the only one milking or doing anything else, so I trusted myself.