crk1a

I was contacted by a customer who has just moved into an old home. She says there are several issues that need addressed, such as warm wall plates, fans and lights turning on in the middle of the night, etc. The neighborhood is an historic district that I have worked in before, but my troubleshooting old knob and tube is somewhat limited. Any advice on what to look for would be greatly appreciated. Thanks

480sparky

You need three tools:
1. Ammeter, to check for obvious overloads.
2. Megger, to check the condition of the concealed wiring.
3. IR thermometer, to check the actual temp of the 'hot' devices.

Unfortunately, K&T is known for buried splices, so there's no way to check them. But other than that, you can 'give it the once-over' the same as you would for any other wiring method (NM, pipe-n-wire, etc).

Chances are, you'll find a lot of loose wires at the devices, which would explain the intermittent and heat problems. You may also find aluminum wiring, itself not a danger, but may need special treatment.

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In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

Rong

And the all important widow maker tester. It is sometimes next to impossible to tell the grounded and ungrounded conductors apart.

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I too am bilingual :
I speak bad English and worser English.

JohnJ0906

I use an extension cord, plugged into a known good receptacle (I add one at the panel if necessary), so you can take a hot, neutral and EGC with you to check each wire.

I don't know if a megger will do anything for knob and tube. I usually see them well separated in the walls - 12" or more.

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John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

frenchelectrican

John .,,

Normally yeah in the wall it useally not a issue but in the ceiling now that can get ya if not carefull lengthwise it is not a issue but crossover now that something it can get ya by suprise.


Most of K&T some are switched netrual so keep in your mind when you try to trace some of the circuits.

Merci,Marc

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Bleu est beau.

JohnJ0906

Good point Marc..... as usual.

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

waco

A common perception of K&T is that it is a "good system" as long as its "integrity" has been sustained over the hundred or so years people have fooled with it.

The splices are usually soldered and good and since the wires are separated, the tape the splices doesn't have to be perfect. The problems I have found involve crossed neutrals and hots (I use the same trick another electrician uses to determine the neutral and hot) and bad wires at the devices and bad devices, many of which are "open" and dirt and dust builds up on their contacts.

I think the best thing that can happen to old houses is complete rewires, period. There's nothing quaint about old, worn out wiring with God only knows how much insulation gone from years and years of critters chewing it off.

The neat part is, they usually aren't too hard to rewire.

Good luck.

Billy_Bob

I agree. Also I have pulled off some light fixtures and the insulation behind the fixture has crumbled leaving bare wires (heat from fixture). In one case, it was a metal bathroom wall fixture with an outlet for shavers, etc. Very nasty situation!

I can imagine one of those combo medicine cabinet/light fixtures (all metal) and this happening.

Then I have found lamp cord spliced in the wall to this wiring. Of course after many years, the insulation has just crumbled.

Outlets added in walls with no box - wall all wood/plywood.

All sorts of interesting "surprises" lurking in those walls...