Square D bus bars

westbranch

Just at the local Electrical supplier looking at distribution boxes and noted that the:

100 A 20 slot ,
125 A 32 slot and
200 A 40 Slot boxes

all use the same ground buss bar part # PK 9 GTA therefore they all are 200 A rated bars8)8)

The next size up (250A??) uses a different part #.

Cariboocoot

Re: Square D buss bars

Grounding bus bar, or Hot bus bar?
Since ground ordinarily carries no current it doesn't really matter what its rating is.
It's the bars for Hot and Neutral that make the difference.

westbranch

Re: Square D buss bars

I will check that out next time I am there.

BB.

Re: Square D buss bars

Many panels have a general purpose bus bar that can be an isolated "white wire" bus, or with a ground wire/screw can also be the main panel ground bus too. So, it is very possible and likely that such a bus would have to be rated for the maximum current allowed by the main power bus bars too.

-Bill

Cariboocoot

Re: Square D buss bars

I was thinking that just because the same grounding bar is used in the 100 as the 200 doesn't mean either is actually rated for 200 Amps. Ground circuitry only has to carry current long enough to trip breakers, not continuously.

inetdog

Re: Square D buss bars

Cariboocoot wrote: »

Grounding bus bar, or Hot bus bar?
Since ground ordinarily carries no current it doesn't really matter what its rating is.
It's the bars for Hot and Neutral that make the difference.

Exactly right!

The ground bus is more likely sized to match the maximum number of breakers the panel will hold, rather than the listed amperage.

Not conclusive evidence, but the Square D load centers in the QO (R) and Homeline (R) families divide into two groups:

100-125 amps and 150-225 amps. That suggests strongly to me that the 100 and 125 amp units MIGHT both have 125 Amp busses while the 150-225 units MIGHT have 225 amp busses.

The only ways to tell for sure are to ask Schneider or to look at the part number(s) on the buss assemblies themselves.

niel

Re: Square D buss bars

you guys are overlooking the obvious here and that is the number of slots. a 200a buss will be required to have more connections as there are more breaker slots available. they are more than likely the same, but differing lengths with more or less positions.

inetdog

Re: Square D buss bars

niel wrote: »

you guys are overlooking the obvious here and that is the number of slots. a 200a buss will be required to have more connections as there are more breaker slots available. they are more than likely the same, but differing lengths with more or less positions.

I am actually not overlooking it, but there are numerous sizes (slot numbers) available in the 200 amp capacity. So the part number may vary even though the current capacity stays the same. To make use of the part number information, you would have definitely need to compare panels with the same length busses.

The main breaker and main lug wire sizes are in two groups and the breaker to lug conversion parts which attach to the end of the bus are also available in exactly two part numbers, one for 100-125 and one for 150 -225.

Still only circumstantial. But given the cost of getting parts qualified, they have a good motivation to use common parts.