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Kenny C.
08-03-2008, 09:01 PM
Hello,

I am at a bit of a loss here. I have a 4 gang box in my kitchen, 2 switches run pot lights and the other two don't have any lights attached to them yet (supposed to be a light over the breakfast table and island lights). Right behind the wall is the family room that runs of the same circuit. There is also an outlet attached to this circuit in the living room. Last week I noticed the lights flickering. They got worse throughout the week and now the lights do not work at all (neither kitchen nor family room). However the outlet works fine so I assume there is power is coming from the breaker.

I have exposed all the switches and tested with a volt meter. If I connect the volt meter between live and neutral, I get a reading between 53 and 60 volts. If I connect the prongs of the voltmeter between live and ground I get between 115 and 120 volts. Does this mean a loose connection or could one of the switches be fried (the 4 switches are fed power in series)?

A couple of other points that might give you some clues:


This morning, if I didn't turn the switch on for a while, and then turned it on, the lights would only come on after about 30 seconds
The breaker has gone off twice since we have been having this problem
.

Help!

Wrex
08-03-2008, 10:34 PM
You definitely have a loose neutral somewhere in the circuit the lights being intermittent screams that too.

Switches don't connect hot and neutral (we call that a short :)).

The fact that you get the full 120 volts from hot to ground signifies that the hot line isn't the culprit and the ground connection is fine.

There is no real way to avoid old fashioned troubleshooting on this one.

But to isolate where to look (rather then tear into every junction box in the circuit) I would test every outlet on the circuit until I registered a full 120 volts from hot to neutral that means that it is your problem outlet because the one after it will not register 120 volts.

If all of the junction boxes test bad including distribution points (such as where multiple recepticles tie into one box) then you will have to trace the circuit's wire back to the service panel and check its connection to the neutral buss bar. This though should be a last resort because odds are your problem is in one of the junction boxes.

It's funny I had a similar problem in January in my basement however my problem was a bad ground connection I was registering 115 volts from hot to ground and a normal 120 volts from hot to neutral. In my case it turns out that some idiot improperly wired the grounds. They simply bent the ground wire back on the Romex sheathing and tightened the cable clamp so that the ground would be pressed onto the metal of the box.

So basically the outlet was grounded through the junction box (the proper way to do this is with a green threaded grounding screw) however since it was a humid basement the junction box rusted a bit causing a weak connection. After twisting all the grounds together and installing a pigtail to the ground screw of the outlet I was back in business.

To find the offending recepticle I used the method described before.

jwelectric
08-04-2008, 04:48 AM
Hello,(the 4 switches are fed power in series)?Help!


Well there is the problem. If one goes out then the fact that they are in series will make all go out.
Get them wired in parallel so they will work correctly.

Kenny C.
08-04-2008, 10:22 AM
Found the problem ...

Took your advice and was looking at each outlet on the circuit. Moved the couch and this is what I found ... a melted outlet. I renovated two floors of my house last year from the studs in, and had replaced all the aluminum wiring in the house with copper -- except for a couple of lines that would have meant breaking the drywall in the basement (which I did not renovate). The electricians did not touch this outlet, but I wish they would have noticed the AL wiring attached to a CU outlet that the previous owners must have installed.

Funny thing is, this problem only showed itself after we installed pot lights on the same circuit which we use daily. Before that, there was probably not enough juice running through the outlet to cause a problem.

I am just glad my house didn't burn down. Next time, when I think I smell smoke, I'll trust my instincts ...

jwelectric
08-04-2008, 11:23 AM
Well good, at least now we know nothing was wired in series.

Wrex
08-04-2008, 08:59 PM
Yikes!

That's called galvanic corrosion due to aluminum and copper being dissimilar metals.

Special wire nuts should be used when joining copper to aluminum these nuts have a special paste in them to prevent this reaction between the metals.

Aluminum I wonder whos idea that was?

I believe it was used because at one time it was cheaper then copper :D.

Now shunned into obscurity along with quadrophonic stereo, betamax, and parachute pants :p.

hj
08-05-2008, 07:21 AM
IT was not "somebody's idea", it was the way things were done back then. It is not galvanic action because there was no water to act as an electrolyte. The problem with Al wiring is that it had a large thermal expansion rate, which meant it could deform at connections and then "loosen" when the load was removed and it cooled down. Eventually it creates a high resistance connection which overheats during a load. When the overheating becomes sufficient it either melts the device or starts a fire. This is the reason ANYONE with aluminum wiring should periodically feel ALL switches and outlets to see if they are warm, or unusually warm. Either one could signal a problem.

Kenny C.
08-05-2008, 08:39 AM
Well, I pigtailed the AL wires with copper ends so we should be good now. While I was at it I made sure the other outlets didn't have the same issue.

Thanks for all your help.

jwelectric
08-05-2008, 09:00 AM
Well, I pigtailed the AL wires with copper ends so we should be good now. While I was at it I made sure the other outlets didn't have the same issue.

Thanks for all your help.

Did you use the proper type of connector for this copper to aluminum connection?

If not then you are no better off than you were to start with and maybe worse off if the al. conductor was damaged in the process.

Wrex
08-05-2008, 09:22 AM
IT was not "somebody's idea", it was the way things were done back then.

And how long did it take them too realize this expansion rate? If the wires took years to fail after installation it just reinforces what I say below.

This is why I am suspicious of new technology copper was the tried and true norm then some "explorers" tried something new using the homeowners as guinea pigs. And now years later guess whos are paying the price?



The problem with Al wiring is that it had a large thermal expansion rate, which meant it could deform at connections and then "loosen" when the load was removed and it cooled down. This is the reason ANYONE with aluminum wiring should periodically feel ALL switches and outlets to see if they are warm, or unusually warm. Eventually it creates a high resistance connection which overheats during a load. When the overheating becomes sufficient it either melts the device or starts a fire. Either one could signal a problem

Lets not get carried away here you make it sound like every aluminum connection is a time bomb waiting to blow. Aluminum wire is still used for residential service entrance. From the pole through the meter and to the main breaker along with the supply line for the buss bars in my residence.

Why aren't there widespread failures? Because there are fewer connections compare 4 or 6 with the 30 to 40 of a branch circuit. If there are more places for something to go wrong the probability rises.

jwelectric
08-05-2008, 09:36 AM
Why aren't there widespread failures? Because there are fewer connections compare 4 or 6 with the 30 to 40 of a branch circuit. If there are more places for something to go wrong the probability rises.


There are two reasons why Al. conductors failed. The biggest reason was due to improper installation methods being used, another was the type Al. that was being used.

You are correct in the assumption that the more joints the more likely that there will be a failure due to human mistakes and nothing to do with the materials used.

jadnashua
08-05-2008, 10:04 AM
AL can work, but proper installation methods MUST be performed, or it is a disaster waiting to happen. Not all fixtures are rated for AL, and you really should have a torque screwdriver, calibrated, and know how to use it or a proper crimper. Proper splicing technique is critical. AL forms an oxide coating almost immediately - AL rusts extremely fast. Unlike iron, the coating seals the surface because it is essentially the same size, and not bigger like iron rust (which exposes more elemental iron). Look up thermite reaction if you don't believe AL really likes oxygen. AL also expands and contracts a fair amount compared with some other metals, so getting the proper tension on the joint to compensate and not let things loosen up is required.