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Old Electrical Wiring: How to Use Safely

  • Transcript

    TOM: We’re going to a hair-raising topic with Marty in Iowa. Electric, huh? What’s going on at your house?

    MARTY: My house was originally built in 1906. And it’s had some additions done on it and the wiring is a mess and we’re still using those screw-in fuses. So I was – I guess my question is how many outlets do you have on a fuse and how many lamp fixtures do you have on, say, a 20-amp breaker?

    TOM: OK, well it’s not a question of how many outlets or how many lights. It’s how much power is going through that circuit. Now Marty, do you still have knob and tube wiring?

    MARTY: No, that’s been eliminated. I mean it’s up in the attic but it’s not being used.

    TOM: (overlapping voices) Alright, good. OK. You’re sure that it’s all been disconnected? I mean it may still be physically in the walls and in the ceiling but you’re – it’s been completely disconnected? You didn’t just replace a panel somewhere down the line?

    MARTY: Well, you know what, I didn’t do that. I know the wiring’s up there and I’m pretty sure it’s been disconnected.

    TOM: OK, well I wouldn’t be quite so sure. Because I spent 20 years as a home inspector and I can tell you there were an awful lot of times when I was the first guy to tell a homeowner that they’ve been living with a dangerous wiring system. What you can do is you can get a continuity tester from a home center; the kind that detects a magnetic field. And you go up near those wires and one’s going to be hot and one’s going to be neutral and bring the tester near it and it’ll beep if the wire’s hot. And it’s a good idea to determine this; especially in the attic. Because knob and tube wiring is the type of wiring that’s supported by these ceramic knobs and then ceramic tubes. And in the attic, especially, it’s …

    LESLIE: Where you have insulation.

    MARTY: Right.

    TOM: Well, the interesting thing about this is that it’s designed to be an air cooled system. So you take a 1906 that’s got no insulation; everything’s fine. You move that up to 2007 when we want to have lots of insulation in the attic; now you’re taking insulation and you’re burying this knob and tube wiring which was never designed to be insulated like that and it makes it very unsafe. So you need to find out if the knob and tube is still active and replace that.

    In terms of the fuses themselves, believe it or not there’s nothing wrong with having a fuse box. A fuse, as long as it’s properly sized, is actually very, very safe because it’s going to blow when the circuit pulls more power than what it’s rated for: 15 amps for a branch circuit; 20 amps, typically, for the circuits that are in the garage and the kitchen and that sort of thing.

    So the first thing you need to do, Marty, is to figure out if the knob and tube wiring is active; replace what’s remaining that’s still active. The second thing is if you want to replace the fuse box with a circuit breaker panel, it will be more convenient but it won’t necessarily be safer.

    MARTY: OK. Alright. Sounds like you answered my question.

    TOM: Alright, thanks so much for calling us at 888-MONEY-PIT.

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