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
I don't believe I've ever seen an open neutral on a service, where the
ground was able to carry the load, although if it did carry the load, noone
would notice, and I wouldn't get involved. Typically you have lighting and
appliance imbalances, which tip off the property owner to the problem
Back in the olden days when all the homes were connected tgether by a
solid metal piping systen, nothing would happen. Now days you would
end up with an unbalanced service. One side opf the panel would have
high voltage and the other would be proportionately low. Dirt is a
terrible conductor and your ground rod is pretty useless as a neutral.
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.
Well any one circuit could have normal voltage or have anything
between 0 and 240 volts. I used to work for a photo studio that was
in it's second location. The first one burned up due to this little
problem. The second one also suffered from it on the first floor.
The basement (processing and finishing area where I spent most of my
time, was OK.
Under this conditions you can turn on one light and others may
become brighter or dimmer or some of each. You really don't want this
Note. Having a good ground will not help, unless that ground is
also having problems.
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.
Oct 2016 16:58:30 GMT in alt.home.repair, wrote:
Short answer, yes, it's possible.
If you had both hots still connected to the panel but only lost the
neutral, It can cause some 120volt devices in your house to get 240
instead. While some others will get less than 120volts if this happens.
I believe (I'm sure one of the old timers will correct me if i'm wrong)
whichever has the most resistance on one leg when this happens is going
to get the least amount of power while the ones with less resistance on
the other leg will get far more than they expect.
The old timers (I mean no disrespect with the comment) can explain in
greater detail if the two short videos above are confusing.
Make yourself sheep and the wolves will eat you.
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,
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.
Homeowner knowledge is quite simple to avert such failures. If
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.
How did it find that path? There has to be a connection somewhere that
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.
There is often a slight momentary dimming at the moment of startup of a
refrigerator compressor or central air compressor.
I would guess that what he means is that:
A - there was no proper earth ground to the panel and
B - the gas meter was bonded to the ground system of the house which
is connected to the neutral at the main panel.
Exactly what I was thinking too. I've seen new construction in $1 mil
where a similar motor load will cause lights to dim momentarily at the
long runs. For example, turning on a shop vac. I've seen that
many homes. If the standard was no noticeable
change in intensity ever, you'd probably need to rewire most of the
in the US.
But the earth rod and the transformer ground are not going to carry
enough current to stabilize the load. Loss of neutral between the
house and the service will result in the potential between the two
hots and neutral varying depending on the total load on each side. So
it will be divided just like it is now but not always equally. And
this will affect just about everything in the house as even many 240v
appliances use 120 for some things.
Variation is minimized so that neutral currents do not use other paths
(ie water heater, furnace) to obtain earth via gas pipes. So that higher
voltages do not exist and did not compromise gas line gaskets.
Among many functions of earth ground is to reduce voltages due to a
neutral failure. Had that homeowner reacted properly when lights were
changing intensity (when 120 volt appliances were power cycling). Or had
that homeowner inspected his earth grounds, then his house would not have
Cite a source that agrees It is not an intended function of earthing
because it is not reliable.
As usual from homeownershub, this question was answered almost 3 years ago.
Among the answers - from gfretwell:
"Back in the olden days when all the homes were connected together by a
solid metal piping system, nothing would happen. Now days you would
end up with an unbalanced service. One side of the panel would have
high voltage and the other would be proportionately low. Dirt is a
terrible conductor and your ground rod is pretty useless as a neutral."
*If* you have a typical metal municipal water supply system the neutral
current can run to adjacent houses and back through their neutrals,
using the N-G bonds at all the houses.
(Unfortunately that wouldn't work for westom because he says that a
metal water pipe can't be used as an earthing electrode.)
There is probably about a post a year here of bright/dim lamps caused by
a bad service neutral.
True. (although I've never seen a "transformer ground" - are houses
now getting four wire service entrances?) My point was, though, that
they are bonded together, so if the ground connection is completely
lost, that unbalanced neutral current will try to find any path it can
to ground, which will likely be either a water or gas line (or both)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.