Cleaning bus.

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PetrosA

Senior Member
110.12(B) Integrity of Electrical Equipment and Connections.

Internal parts of electrical equipment, including busbars, wiring terminals, insulators, and other surfaces, shall not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues. There shall be no damaged parts that may adversely affect safe operation or mechanical strength of the equipment such as parts that are broken; bent; cut; or deteriorated by corrosion, chemical action, or overheating.

If you are going by the letter of the law, then you've already committed yourself to replacing the panels according to the part highlighted in red.

BTW, green Scotch Brite is no more abrasive than fine steel wool. If you think the Scotch Brite is excluded, then you must exclude all steel wool as well. And all metal polishing agents like Brasso or even red rouge (as a polish is nothing more than a very very fine abrasive). In fact, the blue Scotch Brite, while not containing any embedded abrasive grit, does have a scrubbing action by virtue of its polymer fibers. How shall we define abrasive?

I think the key to section 110.12(B) is the part I highlighted in blue. Now we have to decide and define what is considered "damaged".

Definitely the question is "has the copper been deteriorated" by the gases it was subjected to? From the photo, I'd say it hasn't. It has a tarnish or patina to it now, but that doesn't mean that there is any pitting or serious oxidation (serious enough to actually deteriorate the copper to a degree affecting its safe and mechanical functionality, and every time you install or replace a breaker you're scratching the copper and no one gets upset about that). Regardless, if this is limited to discoloration, in all likelihood the reaction is finished now that the gases are gone. If you want to give the customer the option to save some money, recommend that they have you come back for periodic inspections for at least two years. That would give you both the peace of mind that you want at a cheaper price.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
I am all for giving them the option but put it writing along with the warning of what could happen will be far more costly and might not happen at good hours. Not sure when is even safe hours over there. Been long time since we been over there. We do like haulover beach
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
It is even a real problem? The black color may not be an issue, it may have about the same conductivity as the original copper. I have worked on equipment in locations where that type of oxide forms almost on day one of operation and the equipment works fine and lasts for years.

What about energizing the panel, putting a high current load on a breaker and checking the voltage drop from the bus to the load side termination of the breaker? Compare that to drop across the same breaker with the same load in a new panel.
 

Jon456

Senior Member
Location
Colorado
I'm still trying to figure out how your two panels got exposed to such a high-concentration of sewer gases. Did decide to turn a porta-potty into a storage locker?
 

zog

Senior Member
Location
Charlotte, NC
The issue with sewer gas is the sulphur, which can cause whiskers to develop.
 

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LJSMITH1

Senior Member
Location
Stratford, CT
The issue with sewer gas is the sulphur, which can cause whiskers to develop.

Those images are of switchgear with Silver Plated conductors, which were exposed to continuous low concentrations of Hydrogen Sulfide. Here is the image information that came with those pictures:

Expansive growth of silver whiskers has been found on primary current conductors of circuit breakers in switchgear at pulp recycling mill. The major environmental factor to initiate the growth is relatively low concentration of Hydrogen Sulfide (H2S). As soon as a thick enough layer of silver sulfide has been formed, metal filaments start to grow virtually everywhere but most intensely in locations usually having elevated temperature while electrical units are energized. Just in two months after previous cleaning, the whisker grows up to several inches (6-8 cm) long and up to 0.04 in (1 mm) thick. Most of the whiskers are made of silver with 1-3 % of copper. The surface of the whiskers long exposed to atmosphere is contaminated with silver sulfide. The growth eventually leads to catastrophic thermal failure.

Of course, the solution would be to enclose the switchgear in an explosionproof enclosure - or a NEMA enclosure that would limit contact with the Hydrogen Sulfide laden environment....or just relocate the switchgear.

Here is a link that shows tin wiskers forming on contacts inside a circuit breaker and causing failures. Very interesting stuff.

http://nepp.nasa.gov/whisker/photos/index.html

While not common on large scale electrical items, it has been of great concern in the electronics field for a long time. Even now, how these whiskers form is not fully understood.
 

LJSMITH1

Senior Member
Location
Stratford, CT
Would Aluminum Buss be resistant to the H2S/Wiskers? I noticed in the pictures that the neutral bar looks pretty good.

Probably, unless they are plated with Silver, Tin, or Zinc. Whiskers only form with these types of platings in certain situations. If its raw aluminum, copper, stainless, or just plain steel (non-plated), there won't be an issue.
 

renosteinke

Senior Member
Location
NE Arkansas
I had a customer ... a 24/7 phone center .... whose bussbars were 'cleaned' by the maintenance guy with a Dremel. every few months I was called because ANOTHER breaker died and the buss connection was toast. With my last visit, they had run out of spare breaker spaces.

Busses sem to be like motor starter contacts ... the tiniest amount of abrasion, and you're setting the stage for rapid deterioration.

While the simple answer is to replace the busses .... finding a panel with the same guts can be a real chore. It seems that there is no alternative to a visit to the parts house, where you open up and examine every panel they have with a tape measure and some good pictures.

Nor can you simply order replacement parts, using the info from the panel. It's amazing how manufacturers - GE in particular - are suddenly unable to indetify their products.

In this case, though, you may be lucky. Breakers typically come with some grease / noalox on their contact points, so the exact spots where the breakers made contact may have been protected.

Still ... if the bussbars are coroded .... what about the breaker insides?
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
It is even a real problem? The black color may not be an issue, it may have about the same conductivity as the original copper.

I tested the bus by laying tester probes(not stabbing with the point) on the breaker stabs and the black showed higher resistance. I now this is less than a controlled test, but it tells me the properties of the stabs have changed.

I'm still trying to figure out how your two panels got exposed to such a high-concentration of sewer gases. Did decide to turn a porta-potty into a storage locker?

These load centers are located in an animal hospital I just roughed in a strip mall. The two lease spaces have been vacant for over a year. The adjoining space had the slab cut, plumbing underground rough started, ran out of money and the connection to the sewer was never capped.
 

brian john

Senior Member
Location
Leesburg, VA
Actually my question would be is it affecting the bus other than the typically black color. If the insulators and insulating material is acceptable.........
 
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