65k breakers

[JRT]

I have a situation where I have a 35k 600a main, but because of availability I can't find 35k branch breakers. Any issue with using 42 or 65k branch breakers with a 35k main?

 

[kwired]

Might want to find out what breakers are series rated with your main.

Otherwise I guess the 42 and 65 should be ok, but you may spend less if a lesser rated breaker is series rated with your main.

 

[augie47]

Generally no problem.
You do need to determine the actual system available fault current to assure the ratings are sufficient.
It is highly possible that branch breaker with a lesser rating such as 14k or 22k can series rate with your main.

 

[JRT]

Generally no problem.
You do need to determine the actual system available fault current to assure the ratings are sufficient.
It is highly possible that branch breaker with a lesser rating such as 14k or 22k can series rate with your main.

L-L is 26,000
L-N is 13,000. 1 pole I can use 22k
The 2 & 3 pole higher than 22k are the hardest to get from Eaton. They just started to stock 65k. I was thinking for sake of availability, it would be easier to use 65k. But the main is 35k. Thanks for the info

 

[curt swartz]

As others have said if you main is Eaton you should be able to find the series ratings online. If not call or have your distributor call Eaton.

I have had main breakers added to panelboard builds to allow for lower rated branch breakers.

 

[SoloTrade2017]

Is this other than a dwelling unit? Per 110. 16

 

[ron]

As long as the breaker is listed for use with the panelboard or switchboard, you can use a higher SCCR. The calculated value is just the minimum.

 

[Fred B]

Usually no problem adding a higher AIC rated breaker than the main so long as the main is rated to meet or exceed the potential AFC provided to it. Understand the reason for a minimum AIC on a breaker or other equipment is to provide a safe interruption in event of a fault to prevent a rapid unintended disassembly of any component within the system, that could happen if the AFC is higher than the equipment is rated to withstand.

 

[smoothops10]

I always see a sticker on the panelboard indicating something to the effect of "The maximum short circuit current rating of this device is [...] RMS symmetrical amps, [...]V. The actual rating is limited to the lowest interrupting rating of any circuit breaker installed." Your original post and fourth post brings up an interesting point - it seems you are trying to rate the panelboard 35k for L-L-L and L-L loads and 22k for L-N loads. I haven't seen this before. I'm not saying it is wrong but generally you see a single SCCR rating on low voltage one-lines.