"Bill" <billnomailnospamx@yahoo.com> wrote in message news:6cijfmF3epirsU1@mid.individual.net...
I've seen "loose neutral" connections on electric service panels, but
never a fully disconnected neutral with the two hots remaining connected.
So I was wondering what exactly would happen if a residential electric service (3 wire 240/120 with neutral) lost just the electric company neutral connection but had a good ground to the neutral bar in the main panel?
Would current flow to the ground connection?
If the load was not balanced between the two hots (only every other
breaker in use at the time [extreme situation]), could the ground wire potentially carry say the full amperage of one of the hots?
Or in other words, should the ground wire in the main electric panel be sized to carry the full load of one leg of the service should this situation happen?
The neutral conductor is the return path for the current back to the transformer. If the transformer as well as the home had a good grounding system and soil conditions were right, current would flow through the earth to the transformer.
If there was not an ideal grounding system in place you could possibly have 220 volts going to circuits that shared a neutral conductor.
The electrical code does not require that your grounding electrode conductor be the same size as your neutral conductor, which incidentally is normally smaller than your hot conductors.
I've seen "loose neutral" connections on electric service panels, but never
a fully disconnected neutral with the two hots remaining connected.
So I was wondering what exactly would happen if a residential electric service (3 wire 240/120 with neutral) lost just the electric company neutral connection but had a good ground to the neutral bar in the main panel?
Would current flow to the ground connection?
If the load was not balanced between the two hots (only every other breaker in use at the time [extreme situation]), could the ground wire potentially carry say the full amperage of one of the hots?
Or in other words, should the ground wire in the main electric panel be
sized to carry the full load of one leg of the service should this situation happen?
I can answer this with experience. A long long time ago, (about 1987) we experience some weird happenings with our lights and whole house fan. The whole house fan is what tipped us off to the problem initially. It all of a sudden just slowed down. Some lights were bright, some were dim. The TV
would not come on. After poking around a bit, i got out the (analog) meter and found some outlets had about 80 volts and others had about 144. Then, some how, i had the brilliant idea of turning on the oven. When i turned
the oven on, the fan went back to normal, the lights normal. The 240v load apparently balanced the system. I was at somewhat of a loss at that point.
I was not near as experience in electrical things at that time. I called an electrician friend of mine, he came down, poked around in the box some and decided to loosen the ground on the buss. "OH! GUESS WHAT? Fire on the ground" he said. I'm like "what's that mean"?. He said "well even though
i've never seen this before, it sure looks like an open neutral. So i get
on the horn with the power company. FYI, it was Kansas City Power and
Light. They come out, and basically look at what i'm experiencing and the first thing the guy does is pull the meter. Then he measures the voltages
on the incoming legs. All is equal. Then he tells me the problem must be
on the inside. Puts the meter back in and the imbalance returns. "yep , he says, problem is on your side". So at this point, i'm at wits end, not knowing what to do, so I calls the fire dept and they say 'do you have a fire'? I says no, but I will, if someone does not fix this power imbalance. So that prompts a little higher level of action from KCPL, and they come out again. The service guy makes all his checks and then talks on the radio for
a while. His supervisor says "you know that sounds like an open neutral".
The guy comes back and says they suspect an open neutral. At that point, I explode. I said "NO SHIT SHERLOCK" I told you guys that 3 hours ago. They
ran a bare wire from my meter can to the service box on the street and lo
and behold, all becomes normal again. (did i mention i have underground service?) They came out the next day and started digging. About a foot
from my water meter, at a depth of about 16" the neutral wire was corroded clean in half. Apparently it had been nicked by the backhoe putting in the water line 10 year prior. Well anyway, they fixed the wire, and all was
good for exactly a year to the day. It was so weird, one year later, HALF
the stuff in the house quit working. I had a dead leg. When they came out,
i explained what had happened the year before and so they dug again. Sure enough, about 2 feet from the neutral problem, one of the hot legs had corroded in half.
Well anyway, that's my long and drawn out story of an open neutral. I
forgot to mention, I took all the documents from the open neutral service down to the KCPL office in downtown KC, Missouri and collected a check for one TV and 2 VCRs. They were fried.
steve barker
"Bill" <billnoma...@yahoo.com> wrote in message news:6cijfmF...@mid.individual.net...
I've seen "loose neutral" connections on electric service panels, but
never a fully disconnected neutral with the two hots remaining connected.
So I was wondering what exactly would happen if a residential electric service (3 wire 240/120 with neutral) lost just the electric company neutral connection but had a good ground to the neutral bar in the main panel?
Would current flow to the ground connection?
If the load was not balanced between the two hots (only every other
breaker in use at the time [extreme situation]), could the ground wire potentially carry say the full amperage of one of the hots?
Or in other words, should the ground wire in the main electric panel be sized to carry the full load of one leg of the service should this situation happen?
On Thu, 31 Mar 2011 13:56:18 +0000, westom wrote:
responding to http://www.homeownershub.com/maintenance/What-happens-when-electric-neutral-cut-disconnected-315303-.htm
westom wrote:
Bill wrote:
So I was wondering what exactly would happen if a residential electric-------------------------------------
service (3 wire 240/120 with neutral) lost just the electric company
neutral connection but had a good ground to the neutral bar in the
main panel?
Obviously an earth ground is not as conductive as a neutral wire. But it does not have to be in most cases.
In a three wire (bi-phase) service, must current entering on one hot
wire leaves on the other. Only current that flows in a neutral is due to imbalance in the load.
A safety ground is not as conductive as the neutral. But it should be conductive enough so that current does not use other paths. For example,How did it find that path? There has to be a connection somewhere that
in one house, the earth ground was completely missing. A neutral wire
broke inside the street transformer. So current took a return path via the gas meter. When insulators finally broke down, the house exploded.
should NOT be there. If the neutral is broken the current does NOT automatically go to the earth ground unless there is an improper connection as these are supposed to be isolated. In a stove the 240 elements will continue to function as long as there are no controls that require 120 as these will all be shut down. That is, a computer controlled stove will
cease to function, but an old fashioned stove with simple controls will
still cook and heat as they use only the opposing hot legs. The neutral is only used where 120 is required.
Homeowner knowledge is quite simple to avert such failures. IfThere is often a slight momentary dimming at the moment of startup of a refrigerator compressor or central air compressor.
incandescent bulbs change intensity when major appliance power cycle, then get the problem eliminates. In most cases, that light intensity change is
a minor problem. In some cases, it indicates a threat to human life. At
no time should lights change intensity due to appliance power cycling. Never ignore the symptom because in rare cases it could be a major human safety threat such as failed neutral.
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