Which disconnect to fuse?

[rrc14]

Let me describe the equipment setup before I ask my question(s).

There are two disconnect switches, one is installed after the service entrance, then the feeder runs 1000', and terminates into another disconnect switch installed on the side of the building before hitting the distribution equipment. Basically, its a circuit that is 1000' long with disconnect switches on each end. The feeder is sized for 100A at 480V three phase.

My questions are regarding which disconnect needs to be fused, or if both need to be fused? I would fuse both disconnects, however, the engineer is indicating that may introduce a coordination issue?

I would appreciate any of your thoughts.

RC--

 

[don_resqcapt19]

Is the feeder inside or outside? What size is the OCPD on the supply side of the first feeder disconnect?

 

[rrc14]

The feeder is installed outside in the ground. The OCPD on the supply side of the first feeder disconnect is sized at 125A.

Thanks,

 

[petersonra]

Let me describe the equipment setup before I ask my question(s).

There are two disconnect switches, one is installed after the service entrance, then the feeder runs 1000', and terminates into another disconnect switch installed on the side of the building before hitting the distribution equipment. Basically, its a circuit that is 1000' long with disconnect switches on each end. The feeder is sized for 100A at 480V three phase.

My questions are regarding which disconnect needs to be fused, or if both need to be fused? I would fuse both disconnects, however, the engineer is indicating that may introduce a coordination issue?

I would appreciate any of your thoughts.

RC--

The feeder is installed outside in the ground. The OCPD on the supply side of the first feeder disconnect is sized at 125A.

Thanks,

How did you come up with 125A OCPD for a 100A feeder?

 

[eHunter]

Let me describe the equipment setup before I ask my question(s).

There are two disconnect switches, one is installed after the service entrance, then the feeder runs 1000', and terminates into another disconnect switch installed on the side of the building before hitting the distribution equipment. Basically, its a circuit that is 1000' long with disconnect switches on each end. The feeder is sized for 100A at 480V three phase.

My questions are regarding which disconnect needs to be fused, or if both need to be fused? I would fuse both disconnects, however, the engineer is indicating that may introduce a coordination issue?

I would appreciate any of your thoughts.

RC--

The end closest to the service.

 

[petersonra]

The end closest to the service.

this appears to be an outside feeder tap that can be of any length he wants. so code wise I do not think it matters.

 

[rrc14]

I want to correct myself the OCPD is rated at 100A and not 125A.

 

[electrofelon]

There are too many unknowns to give an answer. I can come up with scenarios where neither needs to be fused and where you dont even needs the disconnects. We would need to know: what is the protection on the feeder that feeds the 1000' feeder, what is the length of the feeder that is inside the first building, what type of equipment is after the second disconnect, and what type of property is this and do qualified individuals maintain the electrical equipment. The easy answer if I make some assumptions is the second disconnect does not need to be fused.