Panel board ratings?

[kwired]

If by insulation you mean interrupting that's exactly my question.


If it helps, assuming the phase to phase voltage doesn't go over 253 (the max for most of these machines, the ground voltage wont go above 146 volts max. In any case its better than the previous ungrounded delta system since the ground voltage could reach 240 under a fault.
However, the issue is still the breakers being subjected to higher than the lower of the slash rating.


One thing that's confusing is that double pole breakers are available straight rated but only for 10kaic, not 22kaic. Even more interesting is that the straight rated breakers when applied to a corner grounded system are only rated 5ka even though they say 10ka? While the new system will be far away from a corner ground the listings have me confused.


Page 2: http://static.schneider-electric.us/assets/digest/17601.pdf

Not what I meant. If the max voltage to ground is 120 then that is a limitation. But it is more likely max nominal voltage is 120 and you are wanting to apply a max nominal of about 139. Now I think that the two and three pole breakers that are straight 240 volt rated would be just fine, after all they are fine when used with a 208 volt high leg.

Also check series ratings with upstream devices, you may still be able to go over 10kA if the right device is upsteam. If not you may need to go to the NF or I line series breakers to get the ratings you need. Plus the QO 2 pole straight 240 volt breakers are going to be expensive enough to justify looking into the NF series as an alternate anyway.

 

[mbrooke]

Not what I meant. If the max voltage to ground is 120 then that is a limitation. But it is more likely max nominal voltage is 120 and you are wanting to apply a max nominal of about 139. Now I think that the two and three pole breakers that are straight 240 volt rated would be just fine, after all they are fine when used with a 208 volt high leg.

Also check series ratings with upstream devices, you may still be able to go over 10kA if the right device is upsteam. If not you may need to go to the NF or I line series breakers to get the ratings you need. Plus the QO 2 pole straight 240 volt breakers are going to be expensive enough to justify looking into the NF series as an alternate anyway.

The thing that makes me scratch my head is that it looks like the more pricy double poles are only rated 10ka, yet the cheaper ones are 22kaic, but slash rated:happysad:. In cases where max fault current does not go above 10ka the 22kaic breakers are the better buy over the 10ka none slash rated ones.

Of course the panels fed by the 225kva bank may have to be changed to I line to get the higher ratings. Fortunately the current main is rated 100kaic, so a series rating might hold for it.


I looked at Schneider's website and whole list of series rated systems are listed.


My only reason for being stuck on the slash rated breaker are the fact the current panels are teaming with 22kaic slash breaker instead of the right ones:roll::happyno: