Aluminum Wiring

[jakebaddog]

My employer has purchased a office/warehouse building that was built in the mid 1960's. During my first inspection of the building's main feed I discovered the following: The main disconnect is a 240vac 3phase safety switch with 75 degree lugs. The conductors are 350 mcm aluminum, and the really bad part is the main fuses are 350 amp. I'm unable to see much more information on the conductor except that it was manufactured by Simplex and C-L-P power cable. The feed is and underground feed in what appears to be rigid metal conduit. I'm trying to determine what types of wiring insulation was available for aluminum conductors in the 1960's so I can properly fuse this switch until building feed is replaced, thanks!

 

[iwire]

Are you sure the conductors are not under the exclusive control of the utility?

 

[jakebaddog]

They terminate at a utility controlled transformer, but the wiring to the building is controlled by the building owner.

 

[iwire]

Then in my opinion your stuck with 250 amp fuses but those could also be a code violation if the NEC calculations indicate a load above 250 amps.

 

[jakebaddog]

250 amps if the wiring is not TW (correct)? I still have to do the load calculations, but judging by the type of building and it's size I'm guessing 400 amps minimum. Thanks for your reply.

 

[iwire]

250 amps if the wiring is not TW (correct)?

Yes. :smile:

 

[masterinbama]

The building was built in the 1960's. Are you sure it is not tin plated copper, it was very common back then.

 

[jakebaddog]

Looks to be aluminum, any idea about the types of wire insulation common to the 60's, thanks!

 

[infinity]

The building was built in the 1960's. Are you sure it is not tin plated copper, it was very common back then.

That would have been first guess. Likely RHW insulation.