Installing standard outlet with 3-phase wiring?

Old 04-08-05, 10:06 AM
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Installing standard outlet with 3-phase wiring?

Hello, All.

I need some help with installing an electrical outlet in what I think is a 3-phase wiring situation.

I live in a New York apartment building that was built in the 1980s (hardly new construction, but a mere child when compared with New York's pre-war buildings).

I'd like to install an outlet next to my kitchen light switch by tapping the wiring already in the switch box. I've done this before without issue in several previous dwellings of varying ages, provided, of course, that the neutral wire is run through the box with the hot wire (not always the case around here...).

However, this time when I opened the switch box, I found a black wire and a red wire connected to the switch (not unexpected), plus a BLUE wire and a SECOND black wire that loop through the switch box without interruption. There is no ground wire per se, but the box and conduit are grounded.

After cutting and reconnecting the blue and 2nd black loops with wire-nuts, a volt meter confirmed that voltage between the blue wire and either of the black wires at approx. 117V, and voltage between the two black wires at approx. 205V. Based on loose info I've picked up over the years, I believe this indicates 3-phase wiring.

Also, turning off the circuit breaker for the kitchen light definitely kills the light circuit, but there was still 117V between the blue and the 2nd black wire. In fact, even after turning off ALL circuit breakers in the apartment, there was still 117V between the 2nd black and the ground.

Anyway, I connected a black pigtail to the black wire on the switch and a white tail to the blue wire, and then connected the tails to the new outlet. My volt meter reports correct voltage, and my outlet tester reports correct wiring (including polarity and ground test).

So, finally, I plugged in a 6-outlet surge-protector, and then plugged into that a single 9-volt DC adapter for my kitchen phone. About 30-minutes later I heard that awful, rude electrical buzz/sizzle that can only mean something is burning up--and my nose confirmed it. Turned out to be the surge-protector.

At first I thought maybe the surge protector had simply died (it was older anyway), so I replaced it with a spare, but the 2nd one also showed signs of distress within 5 minutes of being plugged in.

Needless to say, I've removed all plugs from the new outlet until I can get a handle on what the situation is. Can anyone guess as to what the issue may be? Could I have a phase problem? Any and all suggestions will be greatly appreciated!


Old 04-08-05, 10:14 AM
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I would be a bit leery of connecting a new outlet to wiring that you can't shut the power off to.

A neutral wire is never blue and you should never try to use a blue wire as a neutral. It appears that you have no neutral wire in the switch box, and thus cannot get power for a new receptacle from there. You probably need to look elsewhere for power.

You scare me some. I hope you're scaring yourself as well.
Old 04-08-05, 10:16 AM
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Apartment = you don't own the building.

Don't touch the wiring.

Have the management address the issue.
Old 04-08-05, 04:44 PM
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It's conduit. No problem getting a neutral wire. Just feed it from what ever the light switch controls though the conduit.
Agree you should not be working on an apartment wiring.
Old 04-11-05, 06:26 PM
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I agree with Bob call the super.Your'e lucky you were home when the outlet strip was cooked.
Old 04-12-05, 06:06 AM
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Sounds like you have a three phase 208 service installed in the apartment building. Any phase to neutral will yield 120 volts. You can rewire things yourself, but you could be getting into a pile of trouble doing so. If I were living there I wouldn't want someone else who may not know what they are doing be messing with something that could cause a fire. Since you can't shut off the power, and you don't own the building, let the management do the job.

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