Never assume a wire is powered off!

Doing so could be a deadly mistake...

Mr Mike,

This happened to me yesterday and while it did not occur in a RV it may still apply. the ballast went out on the fluorescent lights in the kitchen. it turns out it is more expensive to buy a replacement ballast than it is to buy an entire new led fixture.

So I made sure the existing lights were off and started to remove the existing fluorescent fixture. in doing so I got a shock from the black (hot) power lead. But I had made sure the lights were off!

In thinking about this I realized that there are different ways to wire a switch into a light circuit so that the switch turns the light off. Power may be fed directly to the light fixture and the switch opens and closes the neutral.

The light will go off but the light fixture is still powered. Moral to the story: use a non-contact voltage tester and verify that the power is actually cut, not just that the circuit is opened. Turn off the circuit breaker if necessary. - Chick D.

Hey Chick,

You are absolutely correct. And this is especially true in older houses that have K&T (Knob and Tube) wiring. So never assume that a wire isn’t hot until you check it with a meter. And never assume a meter or NCTV (Non Contact Voltage Tester) is working unless you first test it on a known hot wire.

Danger, Will Robinson!

There’s an additional danger in RV wiring. Since RVs are always plugged into temporary power source there’s the possibility of a polarity reversal (Hot and Neutral Reversed). While this will show up on a 3-Light outlet tester or EMS surge protector, there’s no obvious signs that anything is wired wrong.

However, now all of the hot-wires in your RV are at ground voltage, and all the neutral wires are at 120-volts. Everything will work as expected, but if you’re working in a live panel and assume the white/neutral wires are okay to touch, you’ll be in for a shocking surprise. And that could be deadly!

Won’t reverse polarity cause a hot-skin voltage?

No, it won’t if the rest of the RV wiring is correct. Since the RV’s neutral is designed to be isolated from the RV chassis, then there’s no fault current or hot-skin voltage created by Reverse Polarity. But if your RV has an internal Ground-to-Neutral bond, then you should create a direct short circuit and tris p the pedestal breaker. And if you also have a broken ground connection in your shore power connection, then the RV chassis will be energized with 120-volts AC at circuit breaker current (30 or more amperes).

Always unplug from shore power before doing any wiring in your RV!

Always unplug from shore power and turn off your inverter or generator before working on anything electrical. And it’s best to do a Lockout/Tagout on your shore power cord.

FYI: I’ve had several readers get shocked when someone else plugged in their shore power cord accidentally and they were wiring in a power center. Luckily they weren’t injured, but it could have been a deadly mistake.

Lock it out!

When I worked on industrial power in the ‘70s each of my electricians and I had our own locks with a unique key that we used to lockout a machine we were working on from accidentally being powered up.

You don’t need to go that crazy for your RV, but don’t just leave your shore power plug laying on the ground next to the pedestal, and don’t depend on simply switching off the circuit breaker. Disconnect your shore power completely from your RV if possible, or at least tape over the plug so it’s obviously not to be plugged in.

And if I was working on RV electrical systems at campgrounds I would consider something like this for a plug lockout. I found it on Amazon HERE.

Let’s stay safe out there… Mike