OLD House wiring issue

stevejvanDecember 11, 2009

So I think I already know the answer to this, but I just want to make sure I am giving the proper advice.

I do a lot of wiring in my own house which is newer, but a friend who just bought an old house (1920's-ish?!) as a foreclosure asked me to help with some electrical issues they have been having.

The room the plan to use as a home office fails a simple recptical plug in test, the error it gives is that the hot and neutral are switched. I opened it up and found two wires, both sold core (not strands, just one piece of wire) and they are wrapped in what looks to be fabric, then inside that is black rubber and a single copper wire. There are two of these. The outlet puts out no electricity. One wire was hooked into the top neutral port, and the other was wired into the bottom neutral port.

When I turned the breaker off, and tried every possible combination of neutral and load configurations half their house did not work after turning the breaker on. As soon as I put it back to neutral & neutral the rest of the house worked, but this outlet did not.

They want this outlet to work so they can use it for their computer, but I feel this is a serious issue and potential fire hazard. Not only because of the obviously old wiring, but also because of the fact that it appears there are missing components to the equation....i.e. a hot wire!

Any advice would be appreciated. They are trying desperately to avoid hiring a pro, but I think this is what they need. I don't want to be responsible if their house burns down.

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Two wires on the same side of the outlet and nothing on the other side of the outlet. Disconnecting them breaks the circuit for everything downstream.

Sounds like things are seriously miswired.

Mid 1920's they were still using knob and tube wiring. They need to replace the wiring - esp because after almost 90 years, it's been hacked more than a few times. This sounds like no exception.

You really don't want to mess with it... Sometimes the right answer is to tell them that they need to hire a qualified person to do it right - even if that's not what they want to hear.

    Bookmark   December 11, 2009 at 2:40PM
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There are a number of options. The best, and the only one I will enumerate, is to replace it.

Your tester shows hot/neutral reversed. Well, the tester needs SOME power to light up its LEDs, so there is a hot there.

My guess is that those aren't neutral wires you've got there - they're hot. Whoever put the outlet in got "neutral" through ground...

"hot/neut swap" on those testers means that there is voltage between the neutral slot and the ground, but NOT between hot and ground.

Thus, I believe the wires attached to 'neutral' are hot, and there is nothing attached to what should be hot.

Have a good looksee at the outlet. Did the installer make some means to attach the "hot" terminals to ground?

It would be a total hack if it were done, and certainly wrong - I'm just trying to make some logical guess as to how the outlet might have ever worked.

    Bookmark   December 11, 2009 at 3:24PM
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In worst case situations, I have played out a temporary single insulated conductor from the panel to the outlet. Connected the conductor to the neutral bar in the panel and then use that temporary neutral to test for the "hots". And for the permanent conductors which do not test hot, the temporary can be used to test continuity back to the panel neutral bar for the existing conductors using an ohmmeter. Do not use an ohmmeter on conductors that might be energized.

    Bookmark   December 11, 2009 at 5:15PM
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I've rewired a lot of knob and tube houses. It's not a fun job, nor is it easy. I don't suggest you even think about diving into this if you are not very experienced, and do not have a decent meter for testing and know how to use it. It can be a real pain to troubleshoot too (totally ignore any wire color if there even is some sort of color other than black) and if you need to repair/add/replace a piece of the system, you're in for a lot of work to have it up to code.
I suggest you get in the attic and check the insulation on the wires also. If it's brittle that means the wire is being overheated, most commonly from the homeowner not using the proper fuse size (a 30 amp in a 20 amp spot) and over loading the circuit. Check the splices also to make sure they're in good shape. Also I'd check with the insurance company. Most around here won't even insure a house with knob and tube/fuses anymore let alone let anything done from a non licensed electrical contractor fly. Not to scare you though... I've seen some knob and tube that looks just as good now as it did I'm sure the day it was installed. It's pretty rare though since the loads of current average day to day living are so much higher than it was in the days of knob and tube.
By the way.... you mentioned you turned off the breaker? Did you mean you pulled a fuse, or has this had a service change/panel replacement?

    Bookmark   December 11, 2009 at 11:16PM
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