280 volt single phase ?? - Electrician Talk - Professional Electrical Contractors Forum

shazam · 04-17-2007, 06:23 PM

Gotta a problem

My 100amp subpanel has 280 vac between the two ungrounded conductors and 141 vac from phase to ground.

I didn't think much of it still we smoke check a couple of 240 volt low bay lamps.

Could a building with puters and fluorescent lighting be functioning off this?

We have had some strong winds in the region and power losses have been numerous. Could POCO have restored it recently and provided us with some strange readings.

How long will puters last with 141vac going to them?

brian john · 04-17-2007, 06:42 PM

There are a variety of issues that may be going on here but we need more information.

Voltage Readings

A-B, B-C, C-A

A-Ground, B-Ground, C-Ground

A-Neutral, B-Neutral, C-Neutral

Neutral to Ground

These readings should be taken with a True RMS multimeter

**MDShunk** · 04-17-2007, 06:43 PM

Oh, my!

Have you taken those measurements with a true-RMS meter, or a regular meter? In any event, my 'oh my!' comment still stands.

Is your 208 coming from your own transformer or the utility's?

Joe Momma · 04-17-2007, 10:23 PM

I thought he said 280 line to line, and 141 line to ground.
Either way I have no guess about the 280, but the 141 sounds like an open neutral. And it appears to be a single phase system(no 'C')

But it seems no one else has any guesses either, some true troubleshooter's round here

In any event what did the other phase read to ground?
If it's an open neutral it would read the difference of 280(possibly 240) minus 141.
If you see one of those possiblility's and this is not from a transformer inside the building then it is the utility company's problem.

Check that out, or I could ask even more redundant questions (C phase, and 208) if that might help......

shazam · 04-18-2007, 06:41 AM

Joe Momma is right, it is single phase NO 208 NO C

The other leg also read 141 to ground.

I have to do some further investigating. I will let you know what I find.

brian john · 04-18-2007, 08:24 AM

Try this again.

What is the line to line voltage.

What is the line (L1 and L2) to neutral voltage.

What is the neutral to ground voltage.

We can't figure out whats wrong if we do not have the information.

brian john · 04-18-2007, 11:01 AM

Without the full information, my guess would be (since your reading on one line is 141 VAC to ground) is your system is not grounded and the system is "floating" or ungrounded. Though as Joe mentioned there may be an open neutral, depending on where you are taking the readings.

If you have an open neutral and you are utilizing this system, you will realize it as you will be frying equipment as the loads change.

Joe Momma · 04-18-2007, 12:05 PM

Quote:

Originally Posted by brian john

Try this again.

What is the line to line voltage.

What is the line (L1 and L2) to neutral voltage.

What is the neutral to ground voltage.

We can't figure out whats wrong if we do not have the information.

He told us from the very start that his voltage is 280 line to line
and 141 a to neutral and b to neutral(ground)

John · 04-18-2007, 12:26 PM

Quote:

Originally Posted by Joe Momma

But it seems no one else has any guesses either, some true troubleshooter's round here

I just showed up.

It appears to be a grounding electrode, a grounding conductor problem or maybe a meter reader problem.
Find and follow the GC to see where it comes from and where it goes to would be a good start. You have to be very carefull when handling the GC it might bite you, use gloves!!

Carry On, that is All.

yanici · 04-18-2007, 12:44 PM

If it's not the meter reading wrong, I think it's time to have the poco check the output from their transformer.

shazam · 04-18-2007, 05:10 PM

I didn't get time to get up to the building today to look into this further.
The panel is dead for the time being.

I want to follow up on what john said about grounding electrode, that is really my gut feeling here.

This building has been here since before my time, with many additions to it.

I will give feedback as soon as I have it.

Joe Momma · 04-18-2007, 08:59 PM

Quote:

Originally Posted by John

I just showed up.

It appears to be a grounding electrode, a grounding conductor problem or maybe a meter reader problem.
Find and follow the GC to see where it comes from and where it goes to would be a good start. You have to be very carefull when handling the GC it might bite you, use gloves!!

Carry On, that is All.

I always look for reasons.........
but carry on, that's all; if you like

At least the reason's are the way I try to answer my questions, although taking shots in the dark I can do also.
If that is the case then I'd say to ask the utility company to check their side of the transformer. Of course tell them all your readings and don't be intimidated by guys like Brian John or MD who act like your readings are something out of a science fiction novel.........

SparksNY · 04-18-2007, 09:18 PM

I'm guessing weak batteries in a cheap meter, or it's the pocos problem. I had a poco worker insist that I must've screwed up wiring something when he was getting 160 phase to ground, turns out he was using a 5 dollar meter with weak batteries. He was humbled when I brought out 2 flukes and confirmed it was his meter that was screwed up.

brian john · 04-18-2007, 09:59 PM

A grounding electrode will have no effect on this issue, a neutral ground bond may.

Joe Momma · 04-18-2007, 10:26 PM

Brian John, as I have been trying to point out........as I have been to everyone for that matter.............

Try to have something to ADD

Instead of discrediting everything, why not actually saying why that such a thing is not so..........

Because to tell you the truth it appears that whenever someone says "that's not right" and can't give any reason, they are just blowing smoke('blowing smoke' means full o' crap)

brian john · 04-19-2007, 11:15 AM

Joe this statement coming from someone who only critizes and ADD NOTHING.. Get Real.

And what I said, THE GROUNDING A ELECTRODE IS NOT AN ISSUE, Why bark up the wrong tree.

John · 04-19-2007, 02:18 PM

The issue is what you are using to measure and what you are measuring against. If the meter you are using is not reading right or the points you are taking measurements from are not correct then your conclusions as to what is wrong is incorrect. A GE and GEC are used as a reference for the electrical system. This is very common it consumer electronics just as it is in the electrical system for a house. If the there is not a good reference point how do you know if you really have 280 Volts? The meter may very well be reading correct, just what you are using for reference points are wrong. This is why I recommended that the GEC be traced to see where it comes from and where it goes to. There might not be a GE or a GEC connected to the sub panel. There is the need to start with the basics, then work on finding the weird stuff.

Carry On!

brian john · 04-19-2007, 06:19 PM

Quote:

The issue is what you are using to measure and what you are measuring against. If the meter you are using is not reading right or the points you are taking measurements from are not correct then your conclusions as to what is wrong is incorrect

Yes this is why I asked for specific readings from specific points, utilizing a true RMS meter.

Quote:

A GE and GEC are used as a reference for the electrical system. This is very common it consumer electronics just as it is in the electrical system for a house. If the there is not a good reference point how do you know if you really have 280 Volts? The meter may very well be reading correct, just what you are using for reference points are wrong. This is why I recommended that the GEC be traced to see where it comes from and where it goes to. There might not be a GE or a GEC connected to the sub panel. There is the need to start with the basics, then work on

While it would be a violation of NEC and I do not recommend it (though un-grounded distribution systems exist), an electrical distribution system will operate without a grounding electrode (GE) and grounding electrode conductor (GEC). These have nothing to do with a reference to what we call a ground or EGC and metallic infrastructure (piping systems, building steel, metal ducts, EGC, ECT).

If a distribution system is installed and the grounded conductor (neutral in a 4-wire wye, corner of a 3–wire delta, the center tap of a 4-wire delta and the center tap in a 3-wire single phase system) is bonded to the metallic infrastructure you’d never know if there was an earth connection or not.

The connection to earth is for minimizing the damage from lightning strikes and other high voltage impulses such as a utility fault.

If you were to only connect to the EG (bond the neutral to the EG) and try to read voltage to earth the readings would be all over the scale and have little or no meaning. Though you could take readings along the length of the GEC and at the GE.

oldman · 04-19-2007, 07:35 PM

Quote:

Originally Posted by shazam

Gotta a problem

My 100amp subpanelhas 280 vac between the two ungrounded conductors and 141 vac from phase to ground.

I have a silly question, i've seen guys fix things once or twice, but since it's a subpanel...anyone check the breaker feeding it in the main?

brian john · 04-19-2007, 07:49 PM

OM:

From a distance without the benefits of hands on troubling shooting at best all I can offer are some suggestions.

What I do when trying to resolve electrical issues is garner as much information as possible. The first step for me in a situation such as this is too measure all available parameters. Based upon the answers to these questions I asked it may be easier to surmise the anomaly, for me. Others may take another approach and this works as well.

It has said if you want 6 ways to do a job get 5 electricians a in a room to discuss the job.

What I suggested is a starting point.