Electrical panel : Ground/Neutral bus bar question


Hi,

In CH type panel CMBE4242B200BTS ( main bus is Copper) , I am trying to replace AL ground/neutral bus bar with

http://www.dinrailwiringduct.com/12-inch-long-ul-listed-copper-ground-bar-or-earth-bar-w-screws-included-and-pre-inserted/

My concern is, most of the Eaton mounting holes are 1-3/4" whereas the Ilsco mounting holes are 2.566".

Should that be concern ? Can I use wire hole as mounting holes ( whichever is aligned to panel holes) ?

Are there any other options for copper Ground/Neutral bus bar ?

Do you guys think if it worth pursuing changing Ground/Neutral bus bar to copper from Aluminum ?

Thanks
diwakarv

Showing 3 responses by jea48

Diwakarv,

How will you electrically/mechanically connect the copper neutral/ground bar to the existing AL, aluminum, bus that feeds the panel from the meter socket? If the AL bus is not made of high strength 6061-T6 aluminum alloy you cannot mechanically bolt the copper neutral/ground bar directly to the AL bus. Even if you were to use an anti-oxidation paste between the two metals, given time the copper will burn itself free from the AL bus.

As for the neutral/ground bars in the CH panel they are not made of regular AL. If they were you could not terminate copper wire to them. They are made from 6061-T6 aluminum alloy and are dual rated for use with copper and aluminum conductors. More than likely they are also electro-tin plated.

Food for thought, the CH 200 amp main breaker in the panel has mechanical lugs made of 6061-T6 aluminum alloy.

Here are a couple of manufacture examples.

Link

Link

I would not mess with the factory installed neutral/ground bar found in the CH Load Center electrical panel. First it will void the UL/CSA assembly listing as well as the manufacture warranty.

If for some reason the electrical connection of your copper neutral/ground bar to the AL bus that is fed from the source utility transformer was broken, became open, the unbalanced 120V load from L1 to source neutral and 120V load from L2 to source neutral could not return to the source on the service neutral. The unbalanced load would then become part of the L1 to L2 series balanced load circuit. That's not good!

Here are a couple of nice videos on the subject.

Link
For this one it would have been nice if the guy would have first used two 120V bulbs of the same wattage. Then when he broke the main neutral connection, thus putting the two bulbs in series with one another, he could have measured the voltage across each lamp and showed the voltage across each bulb around 120V.

After the above example I would of then liked him to change out one of the bulbs to the higher wattage bulb. Then measure the voltage across each lamp again. With this example he would have measured a lower than the normal 120V across the higher wattage lamp load, and a higher than normal 120V across the lower wattage lamp load.

In this video the guy does a little better job.
Link

Thing to remember, only the unbalanced load returns on the main service neutral back to the source. The balanced 120V loads of L1 to neutral and 120V loads of L2 to neutral are in series with one another. It the nature of how a split phase secondary winding of a transformer works.
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Jim

8 (qty) 30 amp breakers feeding 8 (qty) dedicated receptacles. ($80,00)
One 30 amp single pole sub-panel breaker for each metal box duplex receptacle. See 125 amp 2-pole description for more info.

Does not meet NEC code or local AHJ. I bet Krell said it was OK though.

Per NEC Code the maximum breaker size for 2 or more NEMA 5-15R 15 amp rated receptacles is 20 amp.

For a NEMA 5-20R 20 amp rated receptacle the breaker shall be 20 amp, period!
Since it’s a service entrance panel, the neutral/ground is bonded, so I don’t see any issue with changing to a different ground bar.


Do you understand what the guy means when he says the neutral/ground bar is bonded? What that means, and yes that is the case with the meter/Load Center combo unit you bought. The service neutral conductor is bonded, connected, to the meter socket steel enclosure. Inside the Load Center electrical panel the neutral/ground bar is bonded, connected, to the steel metal enclosure again. Yes that is the way it is done. Even where the meter socket is separate from the electrical panel it is Bonded in the same way. (At the meter socket and again at the electrical panel.)

So can / does the unbalanced load current travel on the steel enclosure between the two bonded points as well as the AL bus between the meter socket main service bonded neutral connection and the bonded neutral bar connection? You bet.

What you should have asked the guy, is the AL bus that connects the main service neutral conductor in the meter socket to the neutral/ground bars in the electrical panel made of 6061-T6 AL alloy? That is what you need to bolt a copper neutral/Grd bar to the AL bus. If the AL bus is not 6061-T6 AL alloy and you connect the AL bus to copper the connection in time will fail. Will the bonding screws/straps/steel enclosure carry the unbalanced load current back to the utility transformer? ya, I guess.... Will the bonding screws connections to the main service neutral conductor keep the L1 to neutral and L2 to neutral 120V nominal voltage stable? Hopefully.... Will the total resistance of the bonding screws and steel enclosure be less than the AL bus that connects the main service neutral conductor to the 6061-T6 AL alloy neutral/Grd bars? I doubt it...
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