Short Circuits: Why does my 50-amp twist-lock plug only have 3 contacts?

It does have 4 contacts, and here's what you're missing...

Here’s my latest edition of “Short Circuits”

Hey Mike,

Why does the twist-lock plug on my 50-amp RV only have 3 contacts? The plug that goes into the pedestal has 4 contacts, and the diagram you show has 4 wires. What am I missing? - Confused in Connecticut

Dear Confused,

Your 50-amp twist-lock plug does indeed have 4 contacts, but one is not obvious. Here’s how it works…

The 30-Amp Twist-Lock

The 30-amp connector has 3 contacts which I’ve labeled 1, 2, 3 in the picture above. That’s the Hot, Neutral and Ground connections you see in my pedestal testing diagrams.

The 50-Amp Twist-Lock

The 50-Amp connector also has 3 obvious contacts which I’ve labeled 1, 2 and 3. That’s for the Hot-1, Hot-2 and Neutral wires. But there’s also a 4th sliding contact on the outside edge of the connector which I’ve labeled as #4. That’s the ground contact which bonds the chassis of your RV to the incoming circuit breaker panel.

Making Connections….

And in case you’re interested, here’s how a 50-amp shore power cord is wired. But more on that later…

Let’s play safe out there… Mike