Electrical Safety Tip

Just because two switches (one for the bathroom light, and one for the bathroom fan) are located in the same bathroom and 1 inch away from two electrical outlets, do not assume they are all on the same circuit breaker.

Just sharing a painful tip I learned.

Pro tip.

And always test the tester on a known hot first, to make sure it’s working.

Personally, I feel sorta comfortable with those telling me that there is voltage, but I (again, this is just me) wouldn’t grab a wire because it didn’t beep.
I like those little two prong neon voltage testers. And even more helpful is to get the kind where you can see the little bulb from both sides. With those short leads it seems that more often than not, it’s facing the other way and I can’t see it.
They’re cheap, I keep 3 or 4 of them floating around and I wouldn’t touch anything potentially live without testing it with a non-contact tester first.

Also, check ALL the wires for voltage. I always check hot to ground and neutral as well as hot to ground and neutral to ground. Finding a hot neutral is a fun surprise.

It’s pretty common to put lights and receptacles on separate circuits, especially in modern construction. In addition, lighting is usually on a 15 A circuit, and 120 VAC receptacles are usually on a 20 A circuit.

This is probably even more common in a bathroom where the outlets may be expected to power blow dryers and curling irons.
It doesn’t take much to blow a breaker with a hair dryer if the outlet is shared with other things.


I am actually surprised the NEC does not require a dedicated outlet in each bathroom (next to the sink) just for this reason.

It kinda does. The NEC requires a 20a circuit that feeds only the (GFCI protected) outlets in the bathroom.
I say ‘kinda’ because one GFCI outlet is required but you can have more outlets in the bathroom all on one circuit, but you can’t have outlets on that branch that aren’t in the bathroom.

This is according the the 2011 NEC I just glanced at. I didn’t go looking through the 2017 code, but I’d imagine it’s the same.

Don’t assume you can change a light fixture, because the switch is off.

Yes, the black positive wire is interrupted.

I’ve still gotten a jolt through the neutral wire.

It’s still feeding the other fixtures that are on. Sending current back to ground.

I was changing a fixture at night. Needed light to do the job. The vanity lights were on a different switch. I switched off the main light and started replacing it. That wasn’t a good idea.

I don’t think I got the full charge. But it was enough to make me wait until daylight. So I could flip the breaker.

Unverified assumptions about electrical circuits have a way of ending badly.

Me too. But when you disconnect a bunch of wires in a box, and then get jolted by a white wire, the white wire (at the moment you get shocked) is not connected to the circuit breaker box - it is connected to a load that is turned on. The other side of the load is connected to hot.

Yeah, this is pretty common in the new house I bought a couple years ago, and absolutely nothing is marked in the breaker box. If I need to do electrical work, I just don’t trust anything and just throw the main breaker. Weird to think that about fifteen years back at my parents’ house, we put in new light switches and outlets while working on hot wires. Would never do that today.

The funny thing is, the outlet was NOT GFCI, AND it has another load somewhere else. AND the outlet was on an unlabeled switch in the breaker box.

I’d put money on the previous homeowner having issues with the breaker blowing so they added another outlet and grabbed the closest wire for power. Is the other load either on a shared wall or a light in the basement (if it’s a first floor bathroom and an unfinished basement)?

It’s the 3rd floor of a townhouse. I don’t know where the other load is :slight_smile: