Light bulbs are constanly burning out

Nick -- Yes, let's see what it does at other times during the day and night, although higher demand would figure to lower rather than raise the voltage (due to increased losses in the wiring), as you appear to realize. And I'll defer to the comments Jim (Jea48) will most likely offer on the 3 volt offset between neutral and safety ground -- he is more knowledgeable about that kind of thing than I am.

Regards,
-- Al

Can I check the voltage myself with a multimeter? If so how?

Agree with with Al...... But just remember the voltage reading will only be for that moment in time.

I suggest you talk to the other tenants in the 4plex.
See if they are having the same problem with light bulbs as you are.

I asked a question in an earlier post if you noticed if any incandescent light bulbs suddenly get brighter than normal.
With a loose service neutral conductor connection this is typical. The service neutral conductor carries only the unbalanced load back to the source, the utility transformer.

Example, say all Line 1 (L1) to service neutral loads equal 20 amps and all Line 2 (L2) to service neutral loads equal 20 amps. Then 0 amps will return to the source on the service neutral conductor. The two loads are in series with one another. If the loads are constant and do not vary the service neutral conductor could be disconnected and the two loads would continue to operate just fine.

But what if L1 to neutral load increased to 30 amps and L2 to neutral load remained at 20 amps. If the neutral has a good electrical connection back to the source then 10 amps will return on the neutral to the source.

Some simple calculations..... Lets keep it simple.... purely resistive loads. E = I x R

L1 to neutral load 30 amps. Find R (resistance in ohms)
120V / 30 = 4 ohms

L2 to neutral load 20 amps.
120V / 20 = 6 ohms



Here would be a worse case example. The service neutral is completely open, not connect somewhere between the neutral bus at the electrical panel and the source (utility transformer).
L1 to neutral bus loads and L2 to neutral bus loads are in series with one another.

Current is the same in all parts of a series circuit. Find I (current, amps)

L1 loads, 4 ohms total.
L2 loads, 6 ohms total.
R1 + R2 = Rt = 10 ohms

240V / 10 ohms = 24 amps

Find voltage drop across L1 to neutral bus loads.
E = I x R
24 amps x 4 ohms = 96 volts......

Find voltage drop across L2 to neutral bus loads.
24 amps x 6 ohms = 144 volts.....

The above example would be the extreme that could happen in the event of a total loss of a service neutral connection for the given loads.
A loose or corroded service neutral connection will have the same effect but because of resistance within the bad connection the voltage drop variables will change due to the amount of unbalanced load current placed upon it. And just to muddy the water the service
neutral to earth connection integrity becomes part of the equation as well. Most utility companies connect the neutral at the utility transformer to earth ground as well.

So basically in the case of a loose or corroded service neutral conductor where an unbalanced load is present at the electrical panel the Line with the bigger load will have a Line to neutral voltage lower than half the Line to Line voltage, and the other Line to neutral voltage higher than half of the Line to Line voltage. If the balanced load voltage is say 123V Line to neutral, (246V Line to Line), then one might easily see in an unbalanced load condition one side with a voltage of 115V and the other side 131V. And again it all depends how big the unbalanced load is and how loose/corroded the service neutral connection is.

Now you can see why incandescent bulbs could become brighter when the refrigerator kicks on.

Nice explanation, Jim. Thanks!

So if he has a 3V differential between ac neutral and ac safety ground at the particular outlet he measured, let's make the following rough assumptions:

-- 100 feet of wiring from the outlet to where those two lines are bonded together at the service panel.

-- Negligible current flowing through the safety ground wiring.

-- Wire resistance of 1.6 ohms per thousand feet (corresponding approximately to 12 gauge wire). Which would mean 0.16 ohms for 100 feet.

That would mean, if the resistance through the path is what it should be, that he has 3/0.16 = 18.75 amps flowing through the neutral wiring on that line.

Sounds kind of high, suggesting that perhaps the resistance is higher than it should be somewhere in the neutral run.

If so, meaning that losses in the hot side of the wiring are small compared to the losses in the neutral run, the voltage at the service panel for that line would be the 124.5 measured at the outlet + 3 = 127.5 volts.

And if not (if connection integrity is good for all of the neutral path between service panel and outlet), there is presumably also a 3V drop in the hot side of the wiring. That would mean that the voltage at the service panel for that line would be the 124.5 measured at the outlet + 3 x 2 = 130.5 volts.

In either case, these numbers provide added credence to the possibility you have suggested.

Does that all sound right?

Regards,
-- Al

Al, (Jea48 I answer you below)

Here are the readings from throughout the day:
1pm: 124.5v
6pm: 123.0v
10pm: 120.0v
12am: 124.0v
5am: 125.3v
9am: 124.3v

Given the above, it would reasonable to expect that the voltage could reach above 126v.

Jea48,

...if any incandescent light bulbs suddenly get brighter than normal...

The only time the lights dim is when my wife switches on the kettle. The kettle is plugged into the same breaker as the plug that the lights in the main living area are connected to.

If I take a reading on that plug the voltage drop is from 123.8 to 110. (measured across both vertical slots). However, if I measure from the short vertical to the ground then it reads 116v. If I turn off the kettle the reading goes back to the 123.8.

In regards, to other big consumers, I have regular fridge a wine fridge, dishwaser etc... I have never noticed a diming or brightning of the lights as these appliance switch on of off. I live in open concept condo, so I can hear when these appliance switch on and off.

Breaking News!!! As i am writing this, my surge protector just tripped, I measured the voltage and it is at 126.5v.

I guess I should contact my utility company!

One last point regarding my fellow tennants, the bulbs in the hallway are constantly burning out. I have not explicitly raised this issue with any of the neighbours but I will bring it up in our next condo meeting. I am quite sure that this is shared problem.

Thanks for the help it is greatly appreciated!

The only time the lights dim is when my wife switches on the kettle. The kettle is plugged into the same breaker as the plug that the lights in the main living area are connected to. If I take a reading on that plug the voltage drop is from 123.8 to 110. (measured across both vertical slots). However, if I measure from the short vertical to the ground then it reads 116v. If I turn off the kettle the reading goes back to the 123.8.

Nick -- How many watts does the kettle consume? That should be indicated on a label somewhere on it.

Regards,
-- Al