Wiring for Motion Detectors
LESLIE: Dan in North Carolina has an outdoor lighting question. Tell us what’s going on.
DAN: Well, hello there. First of all, I just love your show.
TOM: (overlapping voices) Thank you very much.
LESLIE: (overlapping voices) Thanks, Dan.
DAN: And I listen to you every week. Hey, I have a question. Down my driveway, I have six light bulbs that are 110 volt. I’ve put fluorescent in them and I have a motion detector.
TOM: (overlapping voices) OK.
DAN: When I drive down, it turns the lights on.
DAN: Do I have to have any kind of fuse between the motion detector and then that line of lights?
TOM: No, because the circuit breaker for where this ties into your house, whatever circuit it’s on, that’s where you have the fuse protection.
TOM: You wouldn’t put a fuse between a motion detector and the light bulbs because the motion detector, essentially, is the switch; so you don’t fuse between the switch and the bulbs.
DAN: This is an existing house and there was a fuse in there, in between. And I didn’t know, when that thing blew out, if I needed to just hardwire that across or if I needed to put another fuse in that line.
TOM: Well, listen, if you’ve got old wiring – who knows how this was done but, typically, here’s what would happen. You would run a circuit from the main electrical panel. It would run, basically, down the driveway and up into and including this motion detector that’s turning them on and off. And the circuit breaker itself is what would protect the circuit. So if, for any reason, you had a short or you were pulling too much power, it would turn the entire circuit off. So I can’t imagine why there would be an in-line fuse. If it wasn’t done professionally, who knows what happened? But if it was done professionally, the circuit breaker or the main fuse panel is where you would have the protection for the circuit.
TOM: And the other thing, by the way, since this is an outside circuit, is you would also have a ground fault protection built into that, so that a ground-fault breaker – basically, not only does it sense a wire that’s overheating; it senses a diversion of current to ground source, which is what happens if you’re getting a shock. That’s when you see the outlets that have test and reset buttons in them and they have breakers that way, too.
TOM: So that would be part of that circuit, as well. Listen, Dan, get an electrician to look at it if it doesn’t look like it was built right, because it doesn’t sound like it was. And if you found one thing that looks odd, there may be something else. And since it’s an outside circuit, you want to make sure it’s done correctly.
DAN: OK. And always, thanks, you guys, for what you do. You have great comments and you help a lot of people.
TOM: (overlapping voices) Well, you’re very welcome.
LESLIE: (overlapping voices) Thanks.
TOM: Nice of you to say. Thank you so much and thanks again for calling us at 1-888-MONEY-PIT.