MV Service Dilemma

[xptpcrewx]

Silly question but what exactly is the difference between (i) the overcurrent device referenced in section 230.90(A), which provides overload protection to the service conductors, and (ii) the short-circuit protective device required in section 230.208, which provides short-circuit protection to all ungrounded conductors that the service disconnect supplies?

 

[paulengr]

Silly question but what exactly is the difference between (i) the overcurrent device referenced in section 230.90(A), which provides overload protection to the service conductors, and (ii) the short-circuit protective device required in section 230.208, which provides short-circuit protection to all ungrounded conductors that the service disconnect supplies?

One provides short circuit protection, the other overloads. They CAN be the same device but are sometimes not. For instance circuit breakers are often overcurrent only in distribution to coordinate with downstream loads with fused disconnects or cutouts for short circuit.

 

[xptpcrewx]

One provides short circuit protection, the other overloads. They CAN be the same device but are sometimes not. For instance circuit breakers are often overcurrent only in distribution to coordinate with downstream loads with fused disconnects or cutouts for short circuit.

I understand that much. Can you be more specific by giving me an example of each of these devices?


Sent from my iPhone using Tapatalk

 

[don_resqcapt19]

The device in 230.90(A) is at the load end of the service conductors. You can only provide overload protection with a device installed at the load end of the circuit.
The rule in 230.208 requires that the equipment and conductors on the load side of the OCPD required by 230.90 have short circuit protection. Since this equipment is on the load side of the other device, that first device can, and does in most cases, provide the required short circuit protection.