Mild Shock from Ceiling Fixture

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Old 01-21-08, 02:29 PM
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Mild Shock from Ceiling Fixture

Just installed new ceiling fixture. House has cloth covered wiring...no ground in box. Got the light hooked up and was installing bulbs with power on. Touched light bulb (CFL) and the edge of the metal trim ring on light and got a tingle shock. Any ideas about what I might have done wrong?
 
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Old 01-21-08, 02:33 PM
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Yes, you installed the light bulb with the power on.

Many people recommend that you shut off the circuit breaker when replacing a light bulb. Some people simply turn the switch off.

You should have done one or the other.

As for the problem, it's possible that the ground wire for the light is touching the hot or the neutral wire. What did you do with the ground wire anyway?
 
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Old 01-21-08, 04:40 PM
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Thanks for the prompt response...Ground from the light is connected to the mounting plate which is attached to the box. I'll check all of the connections again. Everything is capped and taped, but I wonder if maybe the insulation is frayed and one of the supply wires is touching the box...
 
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Old 01-21-08, 05:04 PM
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That is certainly a possibility.
 
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Old 01-21-08, 10:41 PM
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Hot to shell instead of tab? Was grounded when installing bulb?
 
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Old 01-22-08, 06:08 AM
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The ground was on when installing bulb...Mounting plate has a green ground screw and that's where it is attached. By shell to you mean the outside of the box itself?
 
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Old 01-22-08, 06:12 AM
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Ray is suggesting that perhaps you got the two wires for the light mixed up and connected the neutral wire for the light to the hot wire in ceiling. That would energize the outside of the light socket, instead of the base. If you accidentally were touching the outside base of the bulb when installint you could get a shock.

Ray may be onto something. You can get a shock from the neutral as well, so even if it;s wired correctly you could have received a shock by touching the base when installing the bulb. This is one reason why you should have the lights OFF when changing bulbs.
 
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Old 01-22-08, 06:39 AM
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Good suggestions...I can only guess which color is which because the cloth insulation looks the same and so does the wire. The box seems to have 3 wires capped together and a single wire makes up the other in the box. My guess was that the 3 together would be the black. Was that a bad assumption?
 
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Old 01-22-08, 06:43 AM
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Bad assumption. Use a meter or two wire tester to verify. I suspect that the three together are the neutrals.
 
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Old 01-22-08, 06:52 AM
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Thanks again -- you guys are really helpful. Old house wiring drives me crazy and since I just bought it I'm still trying to figure out what was done. I have switches that don't do anything, etc. Am holding off bringing in an electrician until I have a complete idea of what I want done and checked. Tough to get an electrician around here...everybody is really busy. I'll test it.
 
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Old 01-22-08, 06:57 AM
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It's possible that the switches USED to do something, but that someone unknowingly made some changes.

For example, the switches may have controlled a receptacle (or half a receptacle) but the receptacle was replaced incorrectly and now the switch does nothing.
 
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Old 01-22-08, 07:57 AM
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The more I think about this I believe you are correct about me choosing the wrong wires. After I swap the wires what would be the best way to test the fixture itself to see if the problem has been resolved...assuming I don't want to touch the bulb and trim ring at the same time? Voltage meter?
 
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Old 01-22-08, 08:07 AM
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Are any of your receptacles grounded? If so run an extension cord from that receptacle to near the light. With light on check for voltage between extension cord ground and lamp shell. Check for voltage between shell and wide slot (neutral) of extension cord.

what would be the best way to test the fixture itself to see if the problem has been resolved.
You say old cloth covered wires. Do you mean knob and tube? If so the switch may be on the neutral not the hot. If so this is a safety problem that must be corrected.
 
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Old 01-22-08, 08:20 AM
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All receptacles are grounded -- House inspector tested all before I bought the house. As far as knob and tube there is no evidence of the old connectors -- everything is running to the breaker box. Wires have covering other than plastic or rubber...supposedly the house was built in late 50's early 60s but now I'm wondering if it was earlier. How would I tell if the switch is on the neutral? If I have multiple neutral wires capped together I'm assuming that that indicates the circuit continues to other outlets or fixtures in the kitchen. Thanks
 
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Old 01-22-08, 08:27 AM
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I don't think your switch is on the neutral.

For a house built in the late 50s or early 60s, I would be suspect that the receptacles are really and truly grounded. Are there any ground wires anywhere that you can see?
 
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Old 01-22-08, 08:37 AM
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I need to check for ground wires...Inspector used a plug-in tester and it indicated grounding but there may not be any actual wires. I'll take a couple of the receptacles apart and look. Always good to know.

The wiring that I see looks more like what was in my old house which was built in the mid to late 1920s. Could be the house is older than was indicated (I just found a history online and it was built in 1939). Never trust a realtor...I should have researched on my own.

Thanks for continuing the thread -- I'm learning a lot.
 
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Old 01-22-08, 08:43 AM
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If a plug in tester indicates a ground, and there is no ground wire and there is nothing else to provide a ground (like metal conduit), then you may have a real dangerous situation on your hand where someone improperly connected the ground on the receptacle to the neutral. The inspector should have at least opened a few receptacles to check for this.

If you do have the above improper wiring, you need to correct it ASAP, as it is a shock waiting to happen and very dangerous.
 
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Old 01-22-08, 11:30 AM
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Why light socket polarity matters:



"A worker was changing the bulb in a light fixture that had been incorrectly wired (polarity was reversed). He inadvertently touched the metal base of the bulb while it was in contact with the socket. He received a severe shock and later died in hospital."

http://www.cdc.gov/eLCOSH/docs/d0300...1/d000361.html

Another problem here is that reverse polarity at the socket increases the chance of accidentally energizing the metal frame of a lighting fixture - you then don't have to be in contact with the socket to receive a shock.
 
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Old 01-22-08, 11:36 AM
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Mark, sounds like you have a situation I'm used to dealing with - the old cloth wrapped wires with the rubber insulations (called LOOM)... Fortunately, mine was inside armored cable, so that carried the ground...
If you're finding that your receptacles are run with 2 wire loom and not in armored cable to provide a ground, you should give serious thought to rewiring these, as it can pose a fire risk...
Additionally, you mention that you have a circuit breaker in the house and it was done in the 1950s? You should check to make sure it is not of the STABLOK variety, as those also pose a fire risk (they were very common in the 50s/60s, before they were recalled due to a number of fires from the breakers not tripping and the company has since gone out of business)...
If you have a voltage tester, try putting one tester into the hot outlet and another into the ground and see if you get a reading (should be 118 or so)... If you do, try disconnecting the power and pulling the receptacle out and seeing where it is actually grounded to (I've seen some where people wire the neutral into the ground..bad..)...
Old wiring is the worst... Always seems to present problems, and half the time they switched neutrals, which is a real nuisance to correct by having to pull new wires...
 
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Old 01-23-08, 06:33 AM
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Just a quick update...I verified that the wiring is enclosed in metal conduit so the grounds are functioning properly. That's a relief. The inspector must have seen the metal conduit during the inspection or he would have noted otherwise.

One final question and I plan to verify this weekend...When I took off the old light and noticed the 3 wires capped together I turned off the switch and tested with a neon tester. As soon as I touched the bundled wires there was a slight spark and the refrigerator turned off and back on. Obviously at least part of the kitchen outlets are fed through this box, but if these are all neutrals should that have happened? Maybe this is the answer to one of my mystery switches. Logically the placement of the mystery switch would indicate that it is the second switch for the kitchen ceiling light. Any thoughts would be appreciated.
 
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Old 01-23-08, 06:48 AM
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Just what do you mean by, "I turned off the switch and tested with a neon tester."

If you put one side of the tester on each switch lead, you did something potentially dangerous at worst and useless at best. This test will tell you nothing.
 
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Old 01-23-08, 07:00 AM
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I wanted to verify that there was no power running through the box because at that time I was puzzled by the capped wires. I guess what I'm asking is the configuration I describe indicative of a 3 way switch configuration with a lead passing through to the outlets. Sorry about the confusion. I appreciated your patience.
 
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Old 01-23-08, 08:44 AM
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Mark, you might have a situation where there are shared neutrals over 2 circuits... This is also not uncommon for older wiring...
If you have a shared neutral, you can turn off the breaker for the circuit you are working on, and still create a spark and read a current by way of the shared neutral since there would be current on that other circuit...
You'd have to follow the conduit back to your breaker panel and see if there is a junction box anywhere...
Also, you should always turn off the breaker when working, not just the switch - if the switch was only switching neutrals, you'd still have a hot wire in the bundle...
 
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