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







Are you all finding my “Short Circuit” articles useful? I sometimes forget just how many unique and specialized gadgets are in an RV.
Very informative as usual.