crap! home electric issue

[masraum]

I have an old house, '67, with Al wiring. We've got Al rated outlets and switches. Tonight the light in a room went out. I thought it was the breaker, but the breaker is not tripped (I turned it off and on and it isn't tripped). I have an unused breaker, so I tried swapping the breakers. Still no go.

If I put a multimeter across the white and black wires with the switch off I get a reading of 78V. When I turn the switch on it goes to .07V. If I take a reading (switch off) across the white and ground I get 120V, and if I take a reading across the black and ground I get 25V. With the switch ON I get 120V from neutral to either white or black.

I have no idea what any of that should read except that with the switch on I should get ~120 across the white and black.

If I wire a bulb across white-neutral or black neutral I get light, but across white-black, nothing.

To me that says that I'm getting power, but am I getting it in the right place? How in the hell can I tell.

[rick-l]

Originally posted by masraum
If I wire a bulb across white-neutral or black neutral I get light, but across white-black, nothing.

Look for an open in the white wire?

Is the light as bright with the white to neutral connection?

[masraum]

I just rechecked, it's not quite as bright from white to neutral as black to neutral.

The whole circuit is out, too, 3 ceiling boxes, 5 outlets, and 4 wall switches.

thanks

[Hugh R]

You may have a burned buss in your breaker. I had a condition where some of the circuits worked and some didn't. You have two copper (hopefully) busses in your breaker box, one side might have dirt/resistance and have to be cleaned up/replaced.

[masraum]

I just plugged one of those outlet testers into all of the outlets on that circuit and they all say that the hot/ground are reversed. No one has done any work on anything recently. I can't even imagine how this has been working like that.

[masraum]

I can see that the breaker has the black wire connected to it.

[masraum]

Rick, I think you may have hit the nail on the head. Now I have to find/repair the problem. I did a search on the internet for "hot to ground reversed" and found a forum with this answer to a nearly identical problem description.

Yes you had a bad neutral connection or open due to those backstabbed outlets. These are notorious for this problem. You did the right thing moving the wires to the screws. When you use those outlet testers and the lights tell you that you have a hot/ground reverse this really is a open neutral indication. When you think about it getting the ground and hot connections reversed would be pretty darn hard to do, especially when you had a working circuit and then it stops working and you havent touched a thing. There are some people that think there are little green creatures running around in your wiring messing with you. The reason you get this hot/ground reverse as I understand is that with other loads plugged in to the circuit...lights, battery chargers etc when your neutral opens somewhere in the circuit you can actully read 120 volts from neutral to ground from backfeed through these other loads on the circuit. Your tester sees that voltage and indicates you have a hot/ground reverse. If you unplug all the loads on the circuit and unscrew the light bulbs and prevent this backfeed then the tester will change to an open neutral indication. Does this make sense to you?

[HardDrive]

I have a nutty idea. Call an electrician.




(Please note that I did not say that I had a cheap idea)

[masraum]

I may end up doing that if I can't find the source of the problem.


When I unplugged everything and turned off all of the switches the tester switched to "open neutral". So the diagnosis is correct. Now I need to figure out where that is. I assume it's in one of the switches, outlets, or ceiling boxes. Just check them all and I should be good.

[masraum]

I guess I'll finish checking things tomorrow. The wife is complaining that I'm making too much noise.

[rick-l]

I can't think of an easy way to fix this.

Start at the box, make sure it is screwed down under the bar. Then start taking apart boxes along the way to check the white wire. All the connections should be accessible.

I like to turn off the breaker when I dig in the boxes then turn it back on to measure things. Less chance of ugly black marks on the wall. Check hot to neutral for a dead circuit or use one of those (Voltage ticks?) that beep when AC is present.

[snowman]

Ok, I am an electronics engineer. I KNOW what the problem is. Dissimilar metals and or corrosion.

Al wire is now banned in most housing applications. Why? Because the connections degrade and can actually heat up to the point where they can cause a fire.

What you can do about it? If the installation isn't to old, sue the builder and make them fix it. Probably no longer an option.

Remove and regrease the connections with the connecting compound for Al wire and retighten them. What you are seeing is the total loss of connectivity in each connection. The IR drop across this connection can cause a fire due to the heat generated by the lousy connection. Some people use a copper to Al wire splice to "fix" this problem at each switch. Don't do it, it will only fail again and is even MORE likely to cause a fire than the first faulty connection.

The ONLY certain and safe way to remedy this problem is to REPLACE the Al wire with copper wire. Could get very expensive, but I know of no other certain way.

You can just retighten all your connections and get your service back, but you are risking burning down your house.

[rick-l]

This reminds me of something I had to deal with in a house I used to own. They ran two 12 ga black wires off two breakers, one from each phase, and one 12 ga neutral. It ran for a relatively long distance and then split into two 115 volt circuits. When the white wire corroded I had no idea of what was going on.

I realize that theoretically this will work just fine but is it safe and has anyone ever seen this?

[CurtEgerer]

>>>I KNOW what the problem is. Dissimilar metals and or corrosion.

Al wire is now banned in most housing applications. Why? Because the connections degrade and can actually heat up to the point where they can cause a fire.<<<


YES! This is a fire waiting to happen - the failed circuit is just a warning sign. Fires can occur with Aluminum wiring with no warning. Please read this CPSC info. There is an approved method of adding copper pigtails.

http://www.cpsc.gov/CPSCPUB/PUBS/516.pdf

[red-beard]

Steve,

My parent House in upstate NY was built in 1965 with Al wiring. They had one outlet fire in a circuit that had heavy current draw (coffee pot).

Please, hire an electrician to go through the wiring and make it safe. It is possible to make it safe with the proper upgrades. It is not worth risking a fire. After you are done, suggest the same to your neighbors, at least the ones you like and the ones where their house is close enough to catch yours on fire..

[turbo6bar]

Originally posted by rick-l
This reminds me of something I had to deal with in a house I used to own. They ran two 12 ga black wires off two breakers, one from each phase, and one 12 ga neutral. It ran for a relatively long distance and then split into two 115 volt circuits. When the white wire corroded I had no idea of what was going on.

I realize that theoretically this will work just fine but is it safe and has anyone ever seen this?

What if you ran the two circuits at max amperage? Wouldn't this put a lot of load on the lone neutral?

masraum, Isounds like you're on the right track. Put the aluminum conductors under the screws. If I am not mistaken, there are recepticles designed for use with Al wiring. I suppose they're designed to deal with the expansion/contraction of aluminum.

[dad911]

Originally posted by turbo6bar
What if you ran the two circuits at max amperage? Wouldn't this put a lot of load on the lone neutral?
.......

Not if the two breakers are connected to different legs in the panel. Then the current current would run through the blacks like a 220 circuit.

[dad911]

Originally posted by snowman
Ok, I am an electronics engineer. .......

What you can do about it? If the installation isn't to old, sue the builder and make them fix it. Probably no longer an option.............

Sure, sue a builder for a 30 year old installation, that was allowed by code at the time, probably inspected also. Don't stop there, why not sue the electrical contractor and the supply house, and the wire manufacturer?

Do you realize, as an electrical engineer, that aluminum wiring is still commonly used today? Not in the 15 & 20 amp receptacle/lighting circuits, but for sub panels, A/C compressors, and the service cables from the street. The issue isn't necessarily the wire, it is the connections. Even copper systems can use some maintenance. I have noticed that after 5-10 years, my screw connections on the circuit breakers and receptacles can take another 1/4 turn or so.

Here is a practical guide for repairs: http://www.inspect-ny.com/aluminum/awrepair.htm

FWIW, I am both a 'Builder' and an 'Electrical Engineer'

[CurtEgerer]

Asbestos under-slab ductwork was code-approved for many years as well

Aluminum is a great material - just not for residential branch wiring circuit connections! The "inspect-ny.com" document is simply copied information from the CPSC link I posted above.

[masraum]

Thanks all. I don't have the money to replace all of the wiring. I've got plenty of "no alox" I think it's called. The goo for Al wiring. When we bought the house we (the FHA actually) required the PO to replace all of the switches and outlets with co/alr units which are designed for the Al wiring. Apparently they aren't really as good as the spiffy crimp (essentially cold weld) connections listed in one document above, but that's what I've got. In the locations where I couldn't find "co/alr" stuff, GFCI's, I used the pigtail method but not with wire nuts and using lots of the no-alox.

I can tell you that I'll not be in another home with Al wiring. I decided that years ago.