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A-6
Specifications
Required Protection
under 110-10 of
NEC 1999
Preferred Fully
Rated Breakers
Breakers Selected
for Device
Protection
Fully Rated
Short Circuit
Interupt Capability
Publication 1394-5.20 — July 2001
Circuit Breakers
While circuit breakers offer some convenience, there are limitations
for their use. Circuit breakers do not handle high current inrush as
well as fuses. The 1394 system needs to be protected by a device
having a short circuit interrupt current rating of the service capacity
provided or a maximum of 100,000A.
If an upstream circuit protection device is rated for the overload
current and short circuit rating, a supplementary circuit protection
device (such as the 1492) can be used as the only 1394 branch circuit
protection device. The upstream fully rated device let-through must be
less than or equal to the 10 kA interrupt rating of the 1492.
The wiring interconnection in Figure A.1 and Figure A.2 provide
examples of the needed protection and follows UL and NEC codes.
Full compliance is dependent on final wiring design and installation.
Figure A.1
Circuit Protection under NEC 1999 110-10 (preferred fully rated devices)
Fully Rated
Fused
Disconnect
Fully Rated
Breaker
Drive
Drive
Required Protection
under 110-10 of
NEC 1999
Preferred Fully
Rated Breakers
Distribution
Block
Breakers Selected
for Device
Protection
Fully Rated
Drive
Short Circuit
Interupt Capability
Fully Rated
Fused
Disconnect
Fully Rated
Breaker
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