When Quality Counts 2 - Electrician Talk - Professional Electrical Contractors Forum

brian john · 04-07-2007, 09:37 AM

This is the MGB (Master Ground Bar) for a commercial office building with a large data center. The intent of this is to try to achieve a single point ground I assume.

Besides the fact the the grounding conductors have tight bends, which can be an issue, a majority of the connections were loose.

Notice the green tape on the EGC's and the strap for support?

Not sure how why this connection was corroded but in lieu cleaning the connection and replacing the connector the preferred method seems to be just add more NO-OX.

oldman · 04-07-2007, 10:07 AM

brian,

i do like the use of penetrox, but I have one serious question-

Why would the bend in the wire make a difference? they aren't breaking the cables. They really aren't extending the distance.

It's an ugly install, that I will say, but why do the bends make a difference? Will the grounding ions not be able to navigate that bend and just fall to the floor?

frank · 04-07-2007, 11:43 AM

I am always wary of corroded ground connectors. This comes from experience, having gotten a nasty shock from one whilst holding onto the darn end to remake a lug.Obviously a fault existed undetected until 'I found it' so beware folks.

Frank

MDShunk · 04-07-2007, 11:44 AM

Quote:

Originally Posted by oldman

It's an ugly install, that I will say, but why do the bends make a difference? Will the grounding ions not be able to navigate that bend and just fall to the floor?

I assume it is because a lightning strike will blow right out the bend.

I like that Penetrox smeared all over. Sorta like, "Hey, this aluminium conductor got all wet and now it's corroding. Let's smear some of this magic grease all over it, and that will cure it."

JohnJ0906 · 04-07-2007, 12:43 PM

"Magic grease"

MDShunk · 04-07-2007, 12:46 PM

Quote:

Originally Posted by JohnJ0906

"Magic grease"

I swear, it must be magic, juding from all the non-compliant uses people claim it has. My favorite was overheard from a big-box store employee telling a customer that he could connect copper to aluminium if he used Penetrox on the conductors and installed a regular wire nut. (in reality, that's not any different than the Ideal purples; they're just prefilled with magic grease)

JohnJ0906 · 04-07-2007, 12:47 PM

The only magic is that it doesn't want to wash out of clothes

MDShunk · 04-07-2007, 12:53 PM

Quote:

Originally Posted by JohnJ0906

The only magic is that it doesn't want to wash out of clothes

I havn't found anything yet that takes Penetrox out of laundry. The uniform people can get it out, but they're using solvents to wash the uniforms that we'd need a license to buy. If I get a real bad shirt or pair of pants that's too good otherwise to throw out, I take it to the cleaners. Maybe only 2 bucks to make it nice again.

JohnJ0906 · 04-07-2007, 01:12 PM

Not really worth it for a t-shirt though. Oh well, I get 3 a year from the company, I got a drawer full. Keep a nice pristine one on the truck for service calls, job sites don't matter so much. Can't see it on the uniform pants (navy blue)

MDShunk · 04-07-2007, 01:23 PM

Quote:

Originally Posted by JohnJ0906

Can't see it on the uniform pants (navy blue)

My pants are navy also. Can't see Penetrox, but you sure can PVC glue. I'm not sure there's anything that takes that out.

JohnJ0906 · 04-07-2007, 01:27 PM

Yup! Got pants and shirts both with glue speckles. I think the clothes will fall apart before the glue comes out

brian john · 04-07-2007, 02:15 PM

Lighting strokes are high voltage, high frequency occurrences, if the intent of a grounding system is to minimize the damaging effects from these impulses, the conductors should be installed as short as possible and with large sweeping bends. A high frequency impulse sees these bends as an high impedance path, and basically these tight bends as an open conductor negating the effectiveness of the grounding system.

Dembones · 04-08-2007, 10:50 PM

Quote:

Originally Posted by brian john

Lighting strokes are high voltage, high frequency occurrences, if the intent of a grounding system is to minimize the damaging effects from these impulses, the conductors should be installed as short as possible and with large sweeping bends. A high frequency impulse sees these bends as an high impedance path, and basically these tight bends as an open conductor negating the effectiveness of the grounding system.

High frequency huh? I thought lightning was DC.

MDShunk · 04-08-2007, 11:16 PM

Quote:

Originally Posted by Dembones

High frequency huh? I thought lightning was DC.

Last I knew, they think lightning can be anywhere between DC and 18GHz.

K&R · 04-09-2007, 08:54 AM

Is there some reason for not just spacing the lugs evenly? Maybe flipping the lugs over and running the wire straight down and into the lugs? All the wire appears to be coming from above. I know the only reason I can come up with is laziness. Most people take the time to measure out conduit spacing weather it's into a panel or on a trapeze. Seem's they should have taken the same time for something like this that has more of a chance of looking shoddy.

brian john · 04-09-2007, 12:00 PM

I was there on an emergency call Easter Sunday and noticed this MGB had been mounted lower, for some reason they raised the MGB, when they did they flipped the bar and loosened the termination connectors mounting hardware.

Lightning is multiple frequencies as noted by Marc. I send some links