I recently began experiencing overvoltage and undervoltage fluctuations
in my home. And as a result, I have lost two small televisions and a
computer monitor. I'm also unable to run any motor loads such as the
refrigerator, washing machine or vacuum cleaner. I also have trouble
with loads such as a toaster or even an iron .
Under noload conditions, with all branch breakers off, I'm measuring
240V L-L and 120V both L-N and L-G at the main. Both line and load side
of the main breaker have the same readings.
With loads on the system, readings range from 80 to 160 volts L-N
depending on the loads.
The utility came out when I was not at home and checked their lines
when all loads were off, not even a clock was plugged-in (absolute
noload conditions) and declared everything on their end to be fine.
They will not return and also said it is not their problem. They
suggest I "check my breakers." My house is served from a tap on an
overhead 240V line which also serves other homes. From the line tap to
my meter the utility says everthing is OK.
I have therefore deduced based on the symtoms I am experiencing that I
likely may have a problem with a neutral conductor(s).
Can someone recommend a systemic approach to troubleshooting this
problem so that I can isolate the affected branch circuit(s). Please be
detailed and technical. For example, if I need to lift each branch
circuit from the breaker and megger it to determine the resistance L-N
and L-G, etc. then I will rent a megger. Do not suggest that I "check
my breakers" because they have not tripped.
I assume that the utility company checked line and load inside the meter.
First tighten the main neutral connection inside of your circuit breaker
panel. Then tighten each and every neutral and ground connection inside of
the circuit breaker panel.
I would also check your main ground connection at the water main. If it is
corroded, replace the ground clamp.
You should also tighten down your main line connections and all of the
circuit breaker terminals.
While doing all of this tightening down you may notice that one or more
terminals requires a few more turns than others. Those may be the source of
your problems. Generally anything a quarter turn or less is not
The position of that statement immediately above this one in your post
has me believing you are measuring those "improper" voltages at the line
or load side of the main breaker, to the neutral wire itself where it
enters the panel from your meter base.
If that's the case, then the "loose disconnection" i.e. a high
resistance connection of a neutral conductor, MUST be ahead of the panel.
If the utility did a proper check all the way to the input side of your
meter base, and if I interpreted yourwords above correctly, then the
high resistance connection must be between the meter base and where the
neutral line enters your breaker panel. I'm not sure how things work
where you are, but around here you have to get the utility to come
around and pull the meter to make it safe to work on the meter to panel
A megger is NOT what you need, you're looking for higher than normal
resistance at a connection along the neutral path from your side of the
meter to the places where your home's loads are connected. A megger is
used to measure high leakage resistances at high voltages.
If I didn't interpret you correctly above, and you are measuring those
unbalanced voltages to the neutral lead connecting strips in the panel
or to the neutral side of a receptical elsewhere in the home where some
load is plugged in, then:
As a start, look for all the binding clamp screws you can find on all
the neutral bus bars in your panel and give all of them a good
tightening. If you're lucky, that'll do it.
But, as always, BE CAREFULL around electricity.
With no load, voltage measurement with a multi-meter doesn't reveal almost
open (high resistance) connection.
Instead, hook up a lamp (anything > 1W) between L1-N and L2-N, one at a
time. If it doesn't light up, there is an open neutral before the panel.
Now assuming the open neutral is after the panel, the suggestion to tighten
all neutral wires in the panel is a easy place to start. If that doesn't
work, then divide and conquer:
Turn on only one breaker at a time and test the corresponding circuit with a
3-light receptacle tester (you can get this for $4 - $8 at hardware store).
Test all outlets in that circuit (or test the first and last one if you know
which is which). If some says ok and some says open neutral, then the open
neutral is somewhere in between.
Repeat for all breakers.
Thanks to everyone for their assistance. After extensive testing and
checking of every oulet in home, I reached the conclusion that the bad
neutral connection was on the line-side of my panel. To make a long
story short, I faxed all my tests results to PECO (my utility) and they
sent a serviceperson out for the third time. Lo and behold, they found
the bad neutral connection where my service connects to their overhead
Congrats! If you can convince them to come out a 3rd time, you must have
presented pretty clear and convincing test results. I wonder why or how they
could fail to find the problem on the first and 2nd time.
How did the neutral connection go bad? Weather related?
The data was clear, convincing and extremely thorough. I was insulted
that they dare suggest that "I check my breakers". Your suggestion to
use a lamp inspired me to take voltage readings of every receptacle in
my home with a uniform 100W load applied. With the voltage reading of
every receptacle and the corresponding L-N voltage readings at the main
breaker made it evident that the problem was on the line-side of my
panel. Had the problem been within my house, one of the receptacle
voltage readings would have been abnormal. All of my readings confirmed
that the voltage on the line-side of the main breaker would always rise
on one leg and drop on the other leg by the same amount regardless of
which receptacle the load was applied to.
There were also no loose neutral connections in the panel.
There had recently been bad storms in the area so the problem may have
been weather related.
My next task is to recover for damaged equipment!
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