Do battery disconnects need current limiting fuses?

[BuffaloBill]

There is a large VRLA battery (2700Ah) being installed in an industrial setting. It has a fault current value of ~32,000A. If the battery disconnect has an SCCR of 10,000, will it always need a current limiting fuse?

Also, assuming I use a current limiting fuse that brings the SCCR up to 200,000. Can I then use 10kAIC breakers in my panel if the battery is the only possible source of fault current? My thought is that since the fuse is designed to blow before the peak fault current is hit, then we should be able to have a lowered kAIC value in the downstream breakers.

 

[don_resqcapt19]

That sounds like you want a series system between the breakers and the fuses. You can only do that with a tested and listed combination of the fuse and the breakers.

 

[BuffaloBill]

That sounds like you want a series system between the breakers and the fuses. You can only do that with a tested and listed combination of the fuse and the breakers.

Do you know if the series system needs to just be tested with breaker and fuse? Or does the DC Panel enclosure itself, also need to be series tested?

 

[don_resqcapt19]

Do you know if the series system needs to just be tested with breaker and fuse? Or does the DC Panel enclosure itself, also need to be series tested?

Just the overcurrent protective devices when you are trying to use the upstream device to reduce the available fault current at the downstream device.

 

[BuffaloBill]

Do all of the breakers that are downstream of the battery and current limiting fuse have to be series tested? Or is it only the first breaker that is directly downstream of the current limiting fuse?

 

[don_resqcapt19]

Do all of the breakers that are downstream of the battery and current limiting fuse have to be series tested? Or is it only the first breaker that is directly downstream of the current limiting fuse?

All of the OCPDs must be part of the series rated system, unless the calculations, without considering the effect of the current limiting fuse, show that the available fault current on the line side of the OCPD is less than its AIC rating.