Microwave and converter fried at campground

wolfe10 wrote:

CA Traveler wrote:

Bobbo wrote:
Correct me if I am wrong, but on a 30 amp circuit, you have a HOT and a NEUTRAL. If the NEUTRAL loses connection (which is what happened to fry his stuff) you have NO CONNECTION. You can only have the 0v and 240v (or low voltage/high voltage) difference if you have both HOTs connected with no NEUTRAL.

You can have very high voltage on 30A due to a open neutral. It happened to me and of course the open neutral was in the CG 120/240V distribution. This is I suspect a rare incident but it happened to me.

Fortunately I had installed a PI full power protector and it disconnected the rig power and no harm. The voltage was displayed on the remote and I could not pull the plug fast enough.

Sorry, not correct.

Yes, on 50 amp (two hots) and open neutral can cause very high/very low voltage.

But, an open neutral on a 30 amp (single hot) will just cause NO POWER.

Actually, it is correct. I finally figured out how it can happen.

Let's say you and I are parked next to each other. (Distance really doesn't matter though.) My 30 amp rig is on L1. Your 30 amp rig is on L2. We share a NEUTRAL from our sub-panel.

Now, the NEUTRAL is cut at the main breaker panel, but not at our sub-panel. I get 120v on L1 through my RV, going out our shared NEUTRAL, to the sub-panel (where it can not go back to the main panel due to the cut wire), then to your RV. Our shared NEUTRAL carries my 120v from L1 to your RV's NEUTRAL where it meets your 120v on L2. My 120v on the shared NEUTRAL is added to your 120v on L2 to give us both 240v.

You can test this. Get a 4 gang box. Put 2 duplex outlets in it and a switch. Run L1 to one of the duplex outlets and L2 to the other. Run the NEUTRAL to the light switch (so you can simulate a broken wire), then from the switch, to BOTH of the duplex outlets. With the switch turned ON, plug in the gizmo to a 4 wire 240v outlet.

Both duplex outlets will register 120v.

Turn OFF the switch, simulating the broken NEUTRAL at the main breaker box. Now, both duplex outlets will register 240v.

The 4 wire 240v outlet is the main breaker panel, and your gizmo is the sub-panel. Your voltage tester is your RV.

Of course, SOMETHING needs to be plugged in to each of the duplex outlets so current is flowing. Otherwise, the duplex outlets are merely open switches themselves. Be sure that whatever is plugged into the duplex outlets is safe at both 120v and 240v because it will see both voltages during the test.