Here is a question from a site visitor that experienced extensive damage to many of his electrical appliances while un-plugging the unit from the supply.
Most of my appliances in my R.V. got damaged when I was dis-connecting from the pedestal. What went wrong? Why did this happen? This is a large motor coach with a 125/250V, 50A electrical service.
I’m going to assume that in all probability you didn’t shut off the supply breaker before you pulled the plug out of the receptacle. This is essential to avoiding the damage that you experienced. Always shut off the supply before you plug in, or un-plug from the pedestal with any R.V., especially with the 50A services.
These plugs are large, stiff, and can be difficult to plug in or pull out. Thus, we tend to wiggle or rock the plug back and forth. What can happen (and obviously did in this case), is that the neutral prong of the plug lost connection before the 2 hot legs did. Without explaining the theoretical details, this can cause a floating voltage throughout the system, and as much as the full 240V supply can be present at your 120V appliances and devices. This over-voltage will damage the appliances in a very short time!
Sometimes the supply can be faulty and have problems as well if the campground or park is not diligent about maintaining their systems. You should always carry a meter or another acceptable testing device with you and check the outlet for correct wiring, voltage level, and polarity before connecting your R.V. to the supply. Check out this article for some more details on this subject.
As they say, and ounce of prevention is worth a pound of cure, so always follow the manufactures recommendation when connecting or dis-connecting your R.V., or any electrical equipment or device. It will save you time, money, and frustration.