Fuse Block and Tap Conductors

[RumblingREX]

Long time reader, first time poster.

I have an interesting problem, my client has an emergency generator feeding their building from a vault located on the premises. They have asked me to install some equipment that is not on the E/G. Since the utility transformer(located inside the vault) feeds directly into the ATS, it limits my options on where to grab commercial power.

There are an empty set of lugs on the commercial side of the ATS. My plan is to use those empty lugs for a set of tap conductors. I only have 25ft to work with and I am installing all my equipment in another room in the vault more then 25ft away. Not much room around the ATS to mount a fused disconnect and meet code.

My question, can I mount a fuse block in an enclosed JBOX 9 ft AFF? It won't be accesable except by ladder. From that fuse block I could run the correct size wire needed to my equipment where I will have a disconnect.

Utility/ATS - 600A service
1/3 A = 200A, tap conductors = 3/0
equipment needs 58A(1.25 included) =60A fuses
#6AWG from fuses to equipment disconnect.

Should I fuse the disconnect at 60A and set the tap conductor fusing to 100A and run #3 instead of #6 so a fault would blow the disconnect fuses and not the tap fuses high up on the wall?

Thanks for the insight on fuse blocks.

Jason

 

[davidbeach]

Without a disconnect, how would you ever change the fuses? Have the utility turn off the power? Far better would be to have the utility supply another service lateral.

 

[waross]

I would suggest a fused disconnect instead of the J-B and fuses. The inspector will probably want it within reach of the floor. If it is protecting the feeds to the new equipment you can probably use an unfused disconnect switch at the new equipment.
I have had similar situations. I have used power from a plant panel and used the control system to prevent the equipment from starting on standby power.
This system has the advantage that the customer can manually start the equipment on generator power if he wants to.
respectfully.