# Electrical mystory



## Larry$ (Dec 29, 2020)

Yesterday I went to the shop. There is some sort of electrical problem there. I can't tell what happened. Very odd. The breaker had kicked out to the CNC router, even though it wasn't being used. We turned the breaker back on and there was a loud buzz indicating a short circuit. But the breaker didn't kick out. Turned it off.  That breaker serves a 208 to 480  volt, 3 phase transformer, that powers the router. On a totally different panel, a circuit for a 120 Volt outlet wasn't working, no breaker kicked. When the dust collector button was pushed (24 volt control circuit that operates the fan and rotary valve contactors) there was a noise and the lights in the laminating area blinked on/off, even though they were off.  I turned the power on at my lathe. It made a buzzing sound. The DRO came on. When I tried the spindle motor nothing happened (3 phase.) I tried the Mill, which is on a different circuit and it came on fine (3 phase.) We tried the exhaust fan for the spray booth and it came on fine (3 phase.)

Strange series of things. The main breaker panel is 400 amp 3 phase Square D, I-line industrial grade ($400 breakers.) The panel that the CNC router is on was added when more power to the shop was needed. It is a totally separate feed from the utility. 400 amp 3 phase.  There are several additional sub panels. The latest one added is for the new offices. A breaker on it tripped while no one was using anything. It was one of those damn GFI breakers that are overly sensitive. 

I have no idea how all this could happen at once.


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## higgite (Dec 29, 2020)

Any thunderstorms in your area lately? 

Tom


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## den-den (Dec 29, 2020)

I suspect a neutral or a ground problem.  Check connections first, one might have been loose and got hot / burned.


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## projectnut (Dec 29, 2020)

I would second den-den's thought.  I've seen lights in a building flash and burn out with a pop, one at a time in a row like the old time flash bulbs.  On other circuits the lights were dim, and clocks wouldn't work.  A little searching found several loose neutral wires.  I tightened them all down and there were no more problems.


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## Larry$ (Dec 29, 2020)

3 phase doesn't use a neutral! Multiple different grounds.  No thunderstorms. Two different service lines from the utility! Multiple different breaker panels.  @ 8:00am the router was fine, office breaker not tripped two hours later multiple problems! Only one person in the shop, no equipment running.


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## Flyinfool (Dec 29, 2020)

The utility could be having an issue with one leg of the 3PH power. I have seen this happen at work One leg was down to 75V and it was messing up all kinds of things from 1ph 120 to 1ph 220 and everything 3PH. Every thing that used that leg was screwy.

Two line from the utility might still be fed from the same utility lines, Some things still draw power even when off


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## kb58 (Dec 29, 2020)

Flyinfool has a good point. Check the three phase voltages and see if they're equal (within reason). If they're good, I think I'd disconnect everything and check the voltages at each outlet before each device is reconnected, and also double check that each is being controlled by the breaker you think it is.


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## Flyinfool (Dec 29, 2020)

When we had the issue at work the utility found the problem about a half mile away from the plant in their lines. We were not the only plant affected.


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## Larry$ (Dec 29, 2020)

Tomorrows project: start checking voltages but it will take a while. 25,000 Sq Ft. shop. A project that has been on the to do list forever is marking each outlet with the panel and breaker feeding. Then make a paper record, maybe a diagram. Several different electrical contractors have done work here. The last one just a week ago. My shop started out 4,000' 30 years ago. Many alterations since.


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## talvare (Dec 29, 2020)

Larry$ said:


> 3 phase doesn't use a neutral!



That depends. If you have 480V, 4 wire, Y configuration, there is a neutral. Are you using 277V lighting in your facility ? If so, there is a neutral.

Ted


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## Larry$ (Dec 29, 2020)

We have 208 V coming in. There are transformers in the building and on tools to convert to the needed voltages. European tools usually use 380-400V, US tools 460/480 V. Some that originally required 220/240V will run on the 208 OK. The local utility will no longer supply 240 due to the wild leg problem and unbalanced loading. Lighting is all 120 V. Some of our European tools have two contactors and a timer that switches them between Y & Delta on 6 lead motors. Common in Europe where the electrical systems don't like the high inrush of direct line starting. I should have had 480 V from the utility to begin with but at the time didn't have the need. One of the last things installed on the 208V  is a 40 HP vacuum pump.  You can hear the wire slap the inside of the conduit when it starts. Should change it to 480!


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## Flyinfool (Dec 29, 2020)

Hmmmmmmm

If you can hear the wires slap the conduit on every start, Are you sure that movement has not worn thru the insulation, or is not getting close to wearing thru, and and causing leakage during the slaps?


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## Larry$ (Dec 29, 2020)

Good point. I was surprised that it would happen at all. Pretty big wire.


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## markba633csi (Dec 29, 2020)

The utility should be willing to come out and check the incoming service for free, and/or tell you if there have been any problems at their end recently
-M


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## brino (Dec 29, 2020)

Larry$ said:


> Several different electrical contractors have done work here. The last one just a week ago.



That alone is interesting........and a good place to start looking!
-brino


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## Bi11Hudson (Dec 30, 2020)

Late as usual, that's me. Seems most troubleshooting has already been covered. There are a couple of points that need to be stressed though. First and foremost is to check the incoming line for balance. If it's not within 5% or so, scream at the utility. Load balance matters too, but is harder to check. The utility can do it if you don't have an electrician "in house".  An "amp-probe" will solve many such problems. But getting into the "entrance" is dangerous. Best electrician is an old timer that shows up with a Simpson 260 and a magnetic Amp-probe. Don't trust the man with a digital anything.

Then you mentioned 460 wye connected with step down or isolation taking place. And a couple other anomolies. Up front was recent work. Is there any way to isolate the "new work" and try the older system? Then there is the compressor(?) slapping the wires when starting. That is a *no-no* by any measurement. The starting load can be as high as 500% for starting. It doesn't last long, but is a major consideration when sizing wire. 

Then the last thing bothering me is the possibility of "delta" distribution from a "wye" source. How old is the original electrical plant? If it is 40-50 years, or more, old, there may be a "grounded delta" system in the mix. Grounded delta was outlawed years ago, but existing systems are "grandfathered" and still allowed. It is seldom (if at all) taught and few are even aware of it. It has a valid reasoning for being used but is highly dangerous. One leg(phase) is intentionally grounded. In a mixed system with wye *and* delta distribution, strange "electrical phenomena" can occur. 

Just remember, you titled the message "Electrical Mystery". That is not so far off the mark, electricity does weird things. When you have solved the problem, the answer is obvious. But finding the answer may well involve standing on one leg, with the opposite eye closed and chanting an Egyptian mantra while holding your mouth "just so".

.


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## Logan Novice (Dec 30, 2020)

Larry$ said:


> 3 phase doesn't use a neutral! Multiple different grounds.  No thunderstorms. Two different service lines from the utility! Multiple different breaker panels.  @ 8:00am the router was fine, office breaker not tripped two hours later multiple problems! Only one person in the shop, no equipment running.



3 phase Delta connection doesn’t include a neutral wire but in 3 phase Star connection there is a neutral.
Loss of the neutral changes the voltage at the star point so, because the phase voltages are influenced by an open neutral, the phase current is also out of sync..


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## Larry$ (Dec 31, 2020)

Problem solved!
The utility had repeating loses of a phase. Nothing appears to be damaged. One older machine had a relay tripped that took us awhile to find. 
This sort of thing could be really expensive. I'd like to see how wild the voltage spikes were each time the lost leg was reconnected.
We don't often lose power. Last year it was when a backhoe cut the main power cable. It made a big notch in the bucket.


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## Janderso (Dec 31, 2020)

Flyinfool said:


> The utility could be having an issue with one leg of the 3PH power


Valid point. That happened to us a few months ago. It was strange. Having one leg down in a business with lots of lighting and equipment had a strange affect on things.


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## Larry$ (Dec 31, 2020)

A long time ago I rented a shop space in a 100 year old building. Delta power, one leg center tapped for 120V single phase. Making for the wild leg phenomena. I had an electrician come in to hook up some stuff. He couldn't figure out why there was the wild leg. When I told him he said I was wrong. Same guy wired a 240V single phase compressor. When he got done and turned the breaker on, there was a pop and smoke, breaker tripped. He said there must have been a "wisker" that just needed to be burned off. Next try same result. I watched when he opened the compressor box. He had swapped a hot leg & ground. So much for licensed electricians.


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## Flyinfool (Dec 31, 2020)

Glad it is solved.
Fortunately you did not have motors running when the phase was down. A 3PH motor that is already running will continue to run on 1PH when a leg goes but it will burn up.

We had to replace a lot of 3ph motors.


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