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200 amp main w/ 2 # 4AWG

Mark P

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A 200 amp main breaker with 2 copper #4 AWG connected. Home built in 50's. Now I know #4 is rated for 100amp, but I can't believe 2 #4 would equal 200 amp. Electrical is not my strong suit, but this just seems silly. Am I missing something?

I'm recommending a sparky evaluate, but wanted some education and oppinions for the TIJ community.



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Good evaluation my friend........

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 conductor).

The Cross Section of (2) # 4 AWG has a Circular Mill of 41740 and do that times 2 would give you only 83,480 circular mills....so basically equal to a # 1 CU at best...lets assume all copper here as it makes it easier.....

So even IF it was allowed ( which it is not via Article 310 ) it would under 310.15(b)(6) only be good for 150A....not 200A.....since a 2/0 CU has a 133,100 circular mill....so to answer your question....your GUT feeling was right and WELL DONE.....WELL DONE my friend.

So in the end.....the parallel conductor is wrong....they are not larger than 1/0 and the conductors themselves are not " EVEN COMBINED" enough for the 200A service.

ie: Circular Mills is the technical size of the conductor for clarrification. Sorry for being so technical....honestly I tried to break it down....:) Electricians use this to size many things using the actual circular mils of the conductor...and I just used it to show why (2) # 4 AWG conductors are not the same as a 2/0 AWG CU conductor.....

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lol...sorry as their is other way to say it. When I post something I like to back up WHY it is and basically for a lack of better term......even (2) # 4's together ( If allowed ) would not handle the 200A panel.....sorry sometimes I over educate but their is a method to the madness.

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  • 1 year later...
Originally posted by AHIS

I know this is an old post, but I found another one. This time it is two #3 hooked to a 200amp main disconnect. The house already passed city inspection, which really annoyed me and my client especially since he works for the city, but not as an inspector.

As Paul pointed out earlier in this thread, it's not allowed. You can only install parallel conductors with 1/0 or larger wire. There's an exception that allows paralleling neutral wires down to #2 under engineered supervision. There's no provision for paralleling #3.

Even if the parallel conductors were allowed, you'd need lugs that were rated for more than one conductor.

- Jim Katen, Oregon

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Thanks Jim, but I understand it is not allowed. I posted the second pic because I find it interesting and just wanted to share it. Also interesting is that both setups were in the same town and both passed city inspection because the city guys never remove the covers. They just walk around with a 3 prong tester and test for GFCI and peeling paint then hand you a bill for $100. Then the realtors use it as a selling point "Passed City Inspection".

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  • 2 weeks later...

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