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tnbuilder
08-08-2009, 11:03 PM
My house has a 200 amp service with an exterior cutoff panel adjacent to the meter base. Breaker 1 is 70 amps for exterior AC/Heating circuits. Breaker 2 is 90 amps and controls the interior load center/subpanel.

According to the 2002 NEC load calc, I currently require 80 amps available from the existing 90 being fed to the interior load center.

I got an electrical permit (based on 2002 NEC), and am starting to wire an addition which includes master bedroom, bathroom, laundry, kitchen expansion. Can I add a third breaker to the exterior cutoff panel/load center and run a new SER, 4 wire cable cable to a new subpanel? The addition needs approx 40 amps. Should I use #4 copper for a 50' run through a crawl space?

Speedy Petey
08-09-2009, 08:27 AM
If the addition needs 40A @ 240v then you can run #6 cable from a 50 or 60A breaker. You can also run the #4cu to a panel off a 100 or 90A breaker.