124.5 volts single phase

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dcooper

Senior Member
Location
Ma
I just finished a project complete gut and remodel of 6 units. New service the whole 9 yards. We habe been done for a couple months 100% signed off and finished.

1st I get a call from the developer asking why the light bulbs keep burning out.
2nd I get a call saying they blew a fuse in 2 120v gas hot water heaters
3rd blew a fuse in a 120v gas dryer.

Hmmmm...

I go there check my neutrals.They were tight.Then I read 124.5 volts on each phase (single phase serice) to ground

So the light bulbs were 120v rated...changed them to 130v rated.

Now the equipment??????? Is the 124.5 volts blowing these fuses?

I have the power company involved but that is just more questions than anwers

What do ya think.... anyone....anyone.....anyone
 

iwire

Moderator
Staff member
Location
Massachusetts
I would not be worried about 125 volts.


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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Not sure what it could be, but the voltage at my panel is 123/246 volts and can go up a volt or two on occasion.
 

stew

Senior Member
Just for drill can you double check with an accurate meter to make sure at the panel that you always have equal voltage at each phase. In other words 124.5 all the time phase to ground. Also what is the phase to phase reading? I assume it is 249? Also are any of theses circuits multiwire branch circuits?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110405-2240 EDT

dcooper:

You need to study the characteristic of various loads and their sensitivity to voltage variations. Do enough searching on the Internet and you will find substantial information.

Tungsten incandescent filament light bulbs have a lamp life that is very dependent upon applied voltage.

From http://www.gelighting.com/na/business_lighting/faqs/incandescent.htm
3. My incandescent bulbs have been failing earlier than the specified life. Why is this?

Incandescent lamp life can be shortened by vibration or shock and supply voltage swings. If a lightbulb is going to be in an environment where it is exposed to vibration or shock, such as a garage door opener light or ceiling fan, you should try to use a lamp with a stronger filament. GE manufactures lamps specifically for these two applications along with the Survivor vibration-resistant and "Ruff-n-Tuff" rough service lamp.

Another cause of general incandescent lamp failure (other than leaving them on all the time) is high voltage. While utilities usually do a pretty good job of voltage regulation, they sometimes have little control. State regulatory boards allow them certain specified leeway because of anticipated load, local load peaks, and other criteria. The allowable limits are usually in the order of ten percent, which on your nominal house voltage of 120 volts would allow a range from 108 to 132.

Incandescent lamps are very sensitive to voltage. A lamp rated at 120 volts, for example, would only last 1/2 of rated life if subjected to 125 volts, or 1/3 of rating if the average voltage applied were 130 volts.

The first thing you should do is to keep track of how long the worst offenders are lasting. How long are your lamps burning? Be sure not to count the time that they are turned off. Typical incandescent bulbs are rated at 750-1000 hours, meaning approximately 2-1/2 changes per year.

The next step may not be easy. The only way to tell what average voltage your bulbs are experiencing is to attach a recording voltmeter to the circuit you are testing so that it records only when your lights are on. This step should only be accomplished by a licensed electrician. If you determine that you are receiving higher than rated voltage you will need to contact your electric utility to fix it.

With lower than rated lamp voltage the lamp life increases.

The voltage you have read of 124.5 V will not remain at that level over long periods. The amount of variation is dependent upon many factors. iwire gave you a useful reference table.

Since other things are failing as well in a short time, and unless the bulbs are subjected to shock. I think you have abnormal voltage conditions at times because the bulb life at your measured voltage is too short.

I would suspect a neutral problem that is intermittent, although there are other possibilities.

At my home I do not have and never have had a neutral problem. Some old photos of plots showing my home voltage for a short time shows some slightly abnormal voltage variations, the periodic repetitive nature is the abnormal factor. The magnitude is quite small. In many typical applications you will encounter the short time variation will be much greater. Longer time analysis of my voltage shows greater variation, but not usually rapid. See photos P22-P25. The red curve is voltage. http://beta-a2.com/EE-photos.html

At the shop a few years back we had a neutral and hot problem at the pole transformers. The system has two transformers Y connected on the primary and open delta on the secondary with a wild leg.

For several years we had very short disturbances with maybe some light flicker and CNC machines shuting down. The occurrences might be months apart. Then things became more often but still seldom and quite random. Then occurrences would occur where lights would flicker, or dim, or brighten. On at least one occasion a floor fan sped up. We got voltage perturbation responses from computer UPSs. Complaints to DTE, the power company, finally got them to install a temporary line monitor. This was on-line for over a month and detected nothing even though we had disturbances. I also set up a simple recorder and saw greater then 135 V on the phase I monitored.

Then late one day things were getting much worse. Called DTE. They sent out a truck, but he wasn't the correct person. Dusk was developing. As this driver waited for the other truck he observed arcing at the transformer terminals. The neutral and one hot were both arcing. I fully believe these were aluminum wires. The transformers were replaced and no problems since then other than substation or further up problems.

With the TED power monitor I have at home it monitors the voltage of one phase and the sum of the power of both phases. It monitors voltage to an 0.1 V level. If connected to a laptop with TED's software then you can collect data over a very long time by saving the collected data once per day. The laptop should be on a UPS.

.
 

Electric-Light

Senior Member
Variation of +/- 5% is allowed per ANSI C84.1, but each 5% increase over rated voltage halves the life of an incandescent lamp, and opposite is true for reduction.

Efficacy is also reduced disproportionately with drop in voltage though.
 

dcooper

Senior Member
Location
Ma
I have checked the voltage at 3 different locations (main feeder luggs comming in, and 2 differnt sub panel lugs) The voltage is the same at all 3 locations. The only connection before the feeder luggs is the power compnay connections. Does this elimiate a loose neutral on my end?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I have checked the voltage at 3 different locations (main feeder luggs comming in, and 2 differnt sub panel lugs) The voltage is the same at all 3 locations. The only connection before the feeder luggs is the power compnay connections. Does this elimiate a loose neutral on my end?
The fact that you have the same voltage from each ungrounded conductor to the neutral indicates that there is not a problem with the neutral.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110406-0755 EDT

don:

That at some instant of time all voltages appear to be normal does not indicate there is not a neutral problem. As I discussed in my first post there is the possibility of an intermittent problem. This may not be detected at the time of doing a single voltage measurement.

The indicated problem implies overvoltage.

This can result from a large overvoltage on a hot supply line. Where would such a spike come from? A lightning strike is one possibility. A malfunction of a voltage regulator is another. I had a low voltage problem from a voltage regulator failure. Switching of a large inductive load is still another.

Quite often an overvoltage results from a poor neutral connection. Without continuous monitoring this may not be easily detected. However, a stress test with a large load change on one phase and monitoring what happens to the neutral in comparison with what should be expected could identify a problem.

I do not think one can easily assume there is not a neutral problem without more extensive voltage monitoring.


dcooper:
I have checked the voltage at 3 different locations (main feeder luggs comming in, and 2 differnt sub panel lugs) The voltage is the same at all 3 locations. The only connection before the feeder luggs is the power compnay connections. Does this elimiate a loose neutral on my end?

Because your work is all new and you have rechecked your work my guess is that you are not the source of the problem.

However, saying the voltage is the same at the different points you mentioned is unlikely. If I monitor voltage in one location for less than a minute I see the voltage jump around a few tenths of a volt. This is not my load changes, but comes from the power company primary. If I go from one location to another there may be a difference of several volts depending upon the load on the circuits.

I do not think you will find the problem without monitoring over an adequate time period without a sample rate of 1 second or better. The needed sample rate is a function of the nature of the overvoltage.

Your other equipment that blew fuses should not have done so without the overvoltage having been much higher than the nominal voltage you read. This might mean 140 to 150 V or higher.

.
 

kwired

Electron manager
Location
NE Nebraska
I have checked the voltage at 3 different locations (main feeder luggs comming in, and 2 differnt sub panel lugs) The voltage is the same at all 3 locations. The only connection before the feeder luggs is the power compnay connections. Does this elimiate a loose neutral on my end?

Depends on what the load is when you checked voltage. Little or no load and your readings will look normal. Apply a moderate unbalance from one line to neutral and resulting voltage change for an open or weak neurtal should be obvoius. I use 1500 watt heat gun for the load for these types of tests.
 

ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
There is no 'overvoltage' it is well within normal power company supply.

I agree. I worked for a distribution power company for 12 years and your voltage is fine. The closer you are to the substation or a voltage regulator, the higher your voltage will be. Voltage regulators are placed on the line to bump up the voltage so the end of the line consumers don't have low voltage. That being said, a bad voltage regulator or regulator control could cause intermittent problems.

You won't get a lot of answers from most of the power company employees. The linemen where I worked weren't trained in these types of things. They built line and hung transformers. They didn't troubleshoot. We had other people to assist customers with power quality issues. I would talk to the power company and ask them to come out and hang a power monitor on the transformer to record voltage and current at 1 second intervals. That's what I did when I was called on something like this. If they have bad equipment, they'll want to know about it and fix it before it causes problems. If you get someone that knows what they're doing, they'll want to know as much as possible, such as the time of day this happens, how many times has it happened, how long has it been going on, how often, etc., etc., etc.

Power companies are required by the state utility board to monitor voltages around their system. They are also required to provide the customer with acceptable voltages.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110405-0913 EDT

iwire:

You are correct that the nominal voltage is well within acceptable limits. I did not say or imply that 124.5 V was an overvoltage. In fact I consider it a likely voltage that one might see.

But the nature of the failures --- bulbs and fuses burning out --- is indicative of an overvoltage problem. Because the indication is that of overvoltage does not mean it has to be a continuous overvoltage. The higher the voltage the shorter will be the duration that may cause the problem. I doubt the fuses in the indicated equipment would blow at 130 V or maybe even at 140 V.

The current in a normal resistive load will increase in proportion to voltage. An incandescent light bulb is not a normal resistive load, but at any given operating point and for small voltage changes it can be considered a normal resistance.

The current into a ferromagnetic circuit (read this as transformer or induction motor) will tend to grow faster than the applied voltage. On an unloaded 175 VA 120 V power transformer I measured the following values today:
Volts Amperes
060 --- 0.010
080 --- 0.015
100 --- 0.052
110 --- 0.079
120 --- 0.112
130 --- 0.204
140 --- 0.255

If the transformer were loaded with a resistive load, then the curve would tend to straighten because the magnetic component would be a smaller portion of the total current.

.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
1st I get a call from the developer asking why the light bulbs keep burning out.
2nd I get a call saying they blew a fuse in 2 120v gas hot water heaters
3rd blew a fuse in a 120v gas dryer.

Since the overcurrent issue has a gas feed as an item in common, I would be thinking about why that would be. Especially since the water heaters would have a very low motor load, just the vent pipe motor.

As far as 'why to the light bulbs keep burning out' look for a commonality. Are all the bulbs that burned out the same brand? Were they on the same circuit? Did they all fail at a certain time of the day?

Tricky problems take some detective work if the instruments show no abnormalities.
 
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Electric-Light

Senior Member
Not all data loggers are the same and I'm only familiar with Fluke and classic loggers.

Fluke DMMs with logging functions are not really meant as a continuous security tape like logging, but it can log on interval and do instant capture on abrupt changes.

Set the 189 or 289 for 5 minute interval and 10% capture. The meter will record the average value every five minutes as well as the minimum and maximum observed during that period, then it will make separate entries for each instant there's a deviation of over 10%. That is the way Fluke software works, specifically meant for glitch catching.

Classic data loggers that log the instantaneous value at specific intervals may miss glitches.
 

dcooper

Senior Member
Location
Ma
one more question????? would it help if I put surge protectors on each sub panel? (If I am getting power surges beyond 124.5 volts)
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
110408-1943 EDT

dcooper:

Maybe or maybe not. Depends upon the cause of the problem. You need to study how typical surge suppressors work, and how their characteristics relate to the devices that have failed.

You really need to find out what is the nature (characteristic) of the voltage transient or sustained overvoltage that is causing the failures. This means instrumentation. Then you figure out what to do.

.
 
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