After my house was struck by lightning last summer, the insurance company sent an electrician to see if there was damage to the wires. The electrician sniffed around a bit, then used a polarity tester on every outlet. I asked him why he was using a polarity tester, and he said the polarity could change after lightning, and he said it could change in some outlets and not others. He was a quack, right?
Aflaaak
Dumb is being kind to him.
RB
B wrote:
"B" wrote in news:Jvz%b.35452$% snipped-for-privacy@twister.southeast.rr.com:
If a check of the main panel showed no dmage, then it was an hourly deal for the ins. co.
According to B :
The polarity is _strictly_ determined by which wire is connected to which screw on the outlet.
Unless a lightning bolt is very fast with a screwdriver, the polarity can't change from a strike.
Well, perhaps not:
1) It could be a time waster to inflate his billing hours.2) He was telling you a minor fib and was really testing whether the outlets were working (a polarity tester will tell him that).
3) He was telling you a major fib and was using the polarity tester to determine whether the outlets were wired right in the first place, because if they weren't, perhaps the insurance company could duck responsibility for some repairs to fried equipment.Or, he could just have been a quack. Or, some combination of all four.
Why not?
Because I think of polarity as indicating whether the voltage on a conductor (e.g., a specific pin of an outlet) is +ve or -ve. With AC, the voltage on a conductor cycles between +ve and -ve.
MB
On 02/27/04 07:50 am Doug Miller put fingers to keyboard and launched the following message into cyberspace:
The A in AC stands for alternating, which is what the polarity does 60 times a second (in the US).
So it is meaningless in AC work.
The term used in AC work is phase, which refers to different timings in the alternations, single (residential) or three phase (commercial).
Phase is meaningless in DC work, since the electricity always flows.
Electronically, you're absolutely right.
However, in usage, house current "polarity" doesn't mean voltage polarity, but rather neutral versus hot polarity. In other words, is the neutral and hot the right way around on a plug?
That's what AC "polarity testers" test.
That's why two prong plugs have a wide and a narrow prong, and the plugs are called, wait for it, "polarized plugs".
When discussing AC electric power wiring, the term "polarity" isn't used in a strict sense of the word. Use of the term is mostly used to distinguish between the grounded conductor (or neutral) and the hot wire(s). If one "checks the polarity" of a light fixture, one is checking to be sure that the "neutral" is connected to the screw shell. The plugs of many appliances are "polarized" (will only fit into a receptacle one way). When one "checks the polarity" of a receptacle, one is checking to see that the "neutral" is connected to the silver (white) screw and the hot is connected to the brass (yellow) screw.
Yeah. Sigh, nothing is ever simple in the electrical world. Except in the rest of the world, where everything is hot.
Yep a big ducky...
The last one of these I did we started with a megger. Induced 1000 volts dc into every wire. Every thing was unplugged, natch. This told us if there were insulation issue on the wires. There were on more than 50% of the conductors.
Then we used a low ohm resistance meter, DLRO and checked every conductor from end to end that did pass the megger. About 20% of these failed.
Ended up rewiring the home completely, ripped out every piece of drywall and replaced everything. The service was toast any way. The home looked like it had measles. The lighting caused the stucco nails to pull out. All over the house. Removed the stucco and re attached the lath. The people had bought a surge protector from the utility as well as some more for inside the house. The utilities guarantee said that they paid for all damage after the installation of these devices. Needless to say the utility does not offer them any more nor the guarantee.
I strongly doubt that your house was hit, unless there is damage. I have never seen lightning actually hit a building with out damage. A friend of mine is researching the EM pulse of lightning strikes into buildings. Does not matter what the building is made of, if there is a strike with in a half mile there are measurable electro magnetic pulses induced into the building and the electrical wiring. Some are pretty high, closer is more scary
If you in a high lightning area. Best contact a licensed lightning protection company for a quote. Have your grounding system tested in your home at your electrical service. your looking for
snip
If you applied a one thousand volt test to a 600 volt wiring system you may have been the cause of the insulation breakdown. A brand spanking new 600 volt system should be field tested at 500 volts. Maintenance testing is usually done at 300 volts.
-- Tom H
The last I saw done was 300v on the conductors. And this is in a location where the insurance companies rarely bother to challenge lightning claims there are so many. Are you sure 1,000v is what you used?
I'll concur, usually *very* obvious damage.
I once had a stack on network cards zapped by a near miss. Sitting on a table in the middle of the room.
Jeff
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