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#15056 - 10/07/02 12:29 PM Lost Your Noodle...?  
mamills  Offline
Member
Joined: Nov 2001
Posts: 745
Wharton, Texas, USA
Good Morning All. Had a rather unusual experience yesterday afternoon at a church bazaar held in a nearly 100 year old community hall where I was providing a sound system. About 1/3 of the way through this, we began having an electrical "event". Some of the lights in the hall suddenly became about 20% brighter, some dimmed, some went out altogether, a few burned out from an obvious overvoltage condition, and the sound system amplifier voltage dropped enough that it started distorting severely. Some of the air conditioning motors (air handlers and condenser units) started humming loudly and every grounded metal enclosure (supposedly grounded...) became energized.

Realizing that we probably had a serious problem with the main service entrance equipment outside, we went to check. There we found that the grounding conductor at the weatherheads (there are two raceways that enter a 400a. main disco) had separated from the POCO conductor. As services go, this is a fairly old one - about 30+ years old. The main disco is nippled into a wire gutter about 7 feet long, with more discos than carter's got liver pills (due to numerous additions over the years). Wiring in this building is a really unique mix - old K & T dating back to the original construction, some wiring done well within code guidelines by experienced professionals, other wiring very poorly done in the worst DIY manner possible (no AHJ in this area, so anything goes, I guess).

I would not want to speculate about whether the grounding conductor opened because of a fault in the system or due to old age. In any event, an electrician (I assume) [Linked Image] laddered the side of the building and, once the main disco was shut off, reconnected the neutral. The power was turned back on again, the lights and air conditioning equipment was checked to be sure that things were in working order, and the bazaar continued without incident for the rest of the day.

It appears to me that this building is in desperate need of a rewiring, or at least a service upgrade. The wiring has been "added onto" so many times, I don't think there is anyone who can vouch for the integrity of the system. The fact that the metal enclosures of outlet boxes, breaker panels, etc. became energized during this "event" probably has me worried more than anything else because the EGC, wherever it is, doesn't seem to be adequate.
The people who own this building are friends of mine, and need to understand that this was truly a dangerous situation.

What be your thoughts?

Mike (mamills)


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#15057 - 10/07/02 04:11 PM Re: Lost Your Noodle...?  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,311
hmmm,
ok Mike,
so you dropped the poco noodle, and mettallic things became hot. Is this church on a municipal h2o line? perhaps that then became the best 'return'?


#15058 - 10/07/02 05:00 PM Re: Lost Your Noodle...?  
mamills  Offline
Member
Joined: Nov 2001
Posts: 745
Wharton, Texas, USA
Sparky:
I was thinking about that, too. The building used to be served by a private water well up until about three years ago. The residents voted in a MUD and a community water system/pumping plant was installed shortly after (and I believe that the vast majority of it was done with plastic pipe). I'm not even sure where the old wellhead/pump was located before the municipal connection came about - never paid much attention to it. The actual plumbing at this hall is every bit as much of a hodge-podge as is the electrical - galvanized steel pipe, copper tubing, plastic pipe. In some parts of the building, there are 3 wire receptacles in surface mounted boxes - fed by some of that old varnished fabric 2 conductor romex stuff that used to be around 50-60 years ago. What's interesting is that they have added an uninsulated wire (looks like 14 awg to me in some places, in others it looks like lamp cord) which exits the box and passes through a small hole in the floor - presumably to the nearest water pipe in the crawl space. Under there is also steel propane gas piping feeding the furnaces in the building which travels about 50 feet underground to a large tank out back.
When I was looking at the service entrance equipment, I did not see any evidence of an EGC - no wire or rod, empty conduit...nothing.

I think you're definitely right...not finding a good EGC, the water system, or worse yet, the gas system, became the "ground".

Mike (mamills)


#15059 - 10/07/02 05:03 PM Re: Lost Your Noodle...?  
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
I'd question the connection to a municipal water system (if there is one) being solid.

Your visual indicator of the lights suggests to me a moderate unbalance of the loads on either side of the neutral. The lack of a low impedance return to the xformer resulted in a simple resistance bridge / voltage divider with enough voltage being on the floating neutral / equipment grounds to be perceptable.


Al Hildenbrand

#15060 - 10/07/02 05:09 PM Re: Lost Your Noodle...?  
BuggabooBren  Offline
Member
Joined: Nov 2001
Posts: 328
NM
When someone yells "Holy Smokes" around there, I'd start running.

From a purely distant perspective (which I'm happy to keep in this case), I'd say they need a wake up call from a sparky who would like to keep congregation safe and who will tell them the potential for disaster that they have in the hodge-podge mix that exists.

Do the insurance companies not mandate some assurances of integrity of facility and services that come in to it?


#15061 - 10/07/02 05:12 PM Re: Lost Your Noodle...?  
ElectricAL  Offline
Member
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
Mike,

Your reply went up while I was composing. With a plastic water supply, I'll bet there is no good way to insure that this event can't occur again. Put in a new service with ground rod and other connections to earth and the return impedance to the xformer will still be high, by comparison to what a metal municipal water system / neighbor's neutral would provide. An event that floats the neutral will still result in the voltage swings.

Al


Al Hildenbrand

#15062 - 10/07/02 05:48 PM Re: Lost Your Noodle...?  
mamills  Offline
Member
Joined: Nov 2001
Posts: 745
Wharton, Texas, USA
Bren: The point about integrity of the mechanical systems for insurance purposes is well taken. I do not know much about that end of things - I assume that they have some kind of fire insurance on the building but I would bet that an inspection has not been done in a long time. They tell me that the electrical system occasionally "burps" (almost to the point of laughing about it)- blown fuses, lights and receptacles which suddenly stop working and then start again without any apparent cause, lights that turn on without being switched on, etc. I have told them that these little "quirks" in the system are signs of some very serious problems that have to be addressed immediately. I've been doing this now for about 10 years, and other people, including electricians and firemen have been after them for even longer. Nothing gets done, and the system "burps" more and more. Eventually, we all know what is going to happen, and if a fire ever gets started in this old building, there will be no stopping it. I just hope nothing goes wrong in the attic while there are 300 people in the building. [Linked Image]

Mike (mamills)

[This message has been edited by mamills (edited 10-07-2002).]


#15063 - 10/07/02 07:21 PM Re: Lost Your Noodle...?  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,311
"burps"
LOL!
[Linked Image]
p.s- when even the nozzleheads notice, it's bad....


#15064 - 10/07/02 11:12 PM Re: Lost Your Noodle...?  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
One possibility is that there was a potential difference between the building/municipal ground electrode and the utility-maintained {pole/pad} ground electrode—causing a voltage gradient leading to the energized enclosures. If any of the sound gear was affected, maybe some sort of under/overvoltage trip/disconnect device in your AC-distribution box would be a wise investment.

I have an long-time associate that used to do commercial sound reinforcement, and before he moved on he’d seriously considered powering all his equipment full-time from his own genset in the alley. Apparently his experience with some public-building electrical systems was not all that wonderful. As for when—in his time the light-show crew was always taking out breakers and fuses at various levels


#15065 - 10/08/02 09:52 AM Re: Lost Your Noodle...?  
mamills  Offline
Member
Joined: Nov 2001
Posts: 745
Wharton, Texas, USA
Sparky:
Yeah, that term was a new one to me too. That's the way they described it to me. IMHO, I think describing it like that is making light of a pretty bad situation. They seem to have a pretty cavalier attitude about the problems that beset this system.

Bjarney:
The bad thing is, I'm not certain where the EGC for the building is located, or if it even exists. I always thought it was supposed to be at the main service entrance, but it ain't there (unless someone did a real good job of hiding it) [Linked Image]. The POCO transformer bank is on a pole about +/- 60 feet from the building. From what little I know about this equipment, everything looks to be in good order. The building service is a 120/240 volt 3ph. delta type with a high leg that reads about 240v to ground. The high leg is apparently used only for the air conditioning equipment. The only other place where this leg appears is in a breaker panel in a corner of the stage, but the breakers inside are so arranged that only the "A" and "B" legs are used (it seems odd to me that the high leg would appear here at all, since this panel only feeds a few convenience rects. and some lights...). The high leg is on "C", which is a departure from what I have learned (that the high leg is supposed to be on the "B" leg - remember, of course that a lot of this system is DIY caliber) [Linked Image].

Mike (mamills)


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