What Happened?

[curious george]

Not sure which thread to start this, so I chose this one as most appropriate.

Model homes in a Tract, garage converted to a sales office. Home ran off generator for approximately 2-3 months. I do not know what type/amperage/condition of generator was used. They had power from the POCO installed approximately 8 months ago.


Tract sold out, now converting the sales office back into a garage. Took the panel cover off the house, and all of the bare ground wires, including the # 4 going to the ufffer, were blackened. You could rub it off, but not easily. It was also on the bare portions of the neutral conductors and the bare portions of the ungrounded conductors, more noticeable on the larger conductors (# 8 ungrounded conductors to the range breaker very noticeable).

The conductors were screwed tight on the terminals.

I know this is not much information, and I do not have Marc?s testers , so I am stumped.

I suspect a ground issue with the generator, but I cannot even find out about how/if it was grounded at the generator. I was not there when the generator was set or installed, and cannot located anyone who was.

All circuits seem to function properly, wiring is just ghoulishly blackened.

Any theories?

 

[zbang]

If you strip back some insulation, is the copper there blackened? Sounds like a chemical problem to me. IIRC sulfides will blacken copper nicely, and sewers can emit nice qualtities of hydrogen sulfide. Maybe bad ventilation or something in the walls. I don't think I'd like to live there...

 

[augie47]

chemical exposure

chemical exposure

can you spell "meth-lab" ?

 

[220/221]

I do not know what type/amperage/condition of generator was used.

Type=Diesel=smoke????

 

[480sparky]

Is there any evidence of a short-circuit to the tub or cover?

 

[haskindm]

Sounds like some sort of chemical reaction with the copper. Any electrical event that would create enough heat to blacken the copper conductors would also damage the insulation on the neutral conductors. Smoke contamination should also be visible on the white insulation which you did not mention. Stripping the wire back a little to see the condition of the conductors that were covered would be a good idea. DEA may be interested in what may have been occuring in this garage.
Be interesting to hear what you determine.
Is the copper in the ungrounded conductors darkened also?

 

[curious george]

Sounds like some sort of chemical reaction with the copper. Any electrical event that would create enough heat to blacken the copper conductors would also damage the insulation on the neutral conductors. Smoke contamination should also be visible on the white insulation which you did not mention. Stripping the wire back a little to see the condition of the conductors that were covered would be a good idea. DEA may be interested in what may have been occuring in this garage.
Be interesting to hear what you determine.
Is the copper in the ungrounded conductors darkened also?

Yes, the ungrounded conductors are also blackened - the larger the conductor, the more prevelant the discoloration.

The panel is located outside, next to the meter (California).

Stripping back the insulation, the conductor is fine - no discoloration.

Smoke does not seem likely, since the insulation is not blackened on any of the conductors - just the exposed copper. Weird...

 

[curious george]

Is there any evidence of a short-circuit to the tub or cover?

Nope! I have looked at this a coouple of times now, really am lost as to a reason. Still think it has to do with grounding at the generator, but I have no way of knowing.

 

[480sparky]

If there was no permanent provision to install a generator, it would seem that they most likely just took the panel cover off and left it off. Maybe it's due to the genny's exhaust.

If nothing else, you should CYA and contact the builder expressing your concerns with this and document the fact you may not provide a warranty for the job due to circumstances beyond your control.

 

[220/221]

Maybe the charge in the wires attracted the smoke particles like the powder coating process?

 

[weressl]

Maybe the charge in the wires attracted the smoke particles like the powder coating process?

AC does not create static or capacitively stored charge, DC does.

 

[electricalperson]

if the panel was outside could moisture be an issue?

 

[don_resqcapt19]

If the only part of the conductor that is discolored is the exposed conductor, then this is likely to have been caused by some airborne contaminate. One that I can think of that does this to copper is H2S, often given off by sewage systems.
Don

 

[brantmacga]

Nope! I have looked at this a coouple of times now, really am lost as to a reason. Still think it has to do with grounding at the generator, but I have no way of knowing.

In your post immediately before this, you said;

Yes, the ungrounded conductors are also blackened - the larger the conductor, the more prevelant the discoloration.

The panel is located outside, next to the meter (California).

Stripping back the insulation, the conductor is fine - no discoloration.

Smoke does not seem likely, since the insulation is not blackened on any of the conductors - just the exposed copper. Weird...

Those are two completely different opinions.

 

[billk554]

could it be 2 different grounds? one from the house (water pipe) and the other from the genn? or maybe the neutral in the gen wasnt bonded to ground and you picked up some crap on the grounds. chanes are the neutral is bonded in the pannel right?

 

[roger]

Is there a swimming pool or pool equipment near the panel?

Roger