What Were They Thinking

Originally Posted By: rmoewe
This post was automatically imported from our archived forum.

These are picture from the inspection that I did yesterday. The main panel is a 200 amp. The service entrance wires from the street are 100 amp. They used split bolts before the masthead to add another 2 GA. wire. I guess this was to make up for undersized wires going to the main. I have never seen this type of installation before.

It sure is nice.

Can someone give me some code verbiage on this installation?

Originally Posted By: bbadger
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Richard this is an example of parallel conductors and it is a

typical practice for circuits above 200 amps.

We often have to parallel conductors for large services,
10 sets of 600 Kcmil are needed for a 4000 amp service.

However this old installation does not meet the current NEC
rules for parallel conductors.

First there is 310.4

310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors
of size 1/0 AWG and larger, comprising each phase, neutral,
or grounded circuit conductor, shall be permitted to be connected
in parallel (electrically joined at both ends to form a single

As you said these conductors are 2 AWG so they are to
small to be paralleled.

Second there is the issue of two conductors under one

That said I do not know if this was wrong when it was installed,
I only know it is wrong now.

Bob Badger
Electrical Construction & Maintenance
Moderator at ECN