Thanks to all gentlemen who steered me in the right direction.
I am going to install a real subpanel in the garage, I will use
3/4" metallic conduit, 6 gauge wires.The subpanel will be protected by a 60 amp breaker on the main panel. It will have the following outlets attached to it, with appropriate breakers:
You might want to consider #4 wire with a 70 amp main breaker. I don't know what you will be using the 50 amp receptacle for, but if you draw 40 amps the 60 amp main will be at its maximum continuous load. Circuit breakers are only rated for 80% continuous load.
John Grabowski
50 amp receptacle will be used for testing military surplus stuff, or, alternatively, later, for a phase converter or some such. Supposedly, #6 wires are rated for 75 amps. i
[Continuous Load. A load where the maximum current is expected to continue for 3 hours or more.] Copyright 2002 National Fire Protection Association
As you can see the definition of continuous is three hours or more.
-- Tom H
no way I would run 50 continuous amps.
i
You need to be aware that the 75 ampere value given in table 310.16 Allowable Ampacities of Insulated Conductors Rated 0 Through 2000 Volts,
60°C Through 90°C are not achievable in actual practice. This is because everything that the conductor connects to has to be listed to be used at the ninety degree centigrade temperature. In general such terminals are not readily available in the market place and that column is used as a starting point for derating the wire for high ambient temperatures or for more than three current carrying conductors in a raceway or cable. The values in the seventy five degree column of the table are the actual maximums that can be practically achieved. Since the 65 ampere value is not a standard size of Over Current Protective Device (OCPD) you are allowed to use a seventy ampere breaker but the idea is that the circuit will only draw sixty five amperes under the designed operating conditions. If you were actually going to draw the full seventy amperes you would go up to the next wire size.-- Tom H
Absolutely great answer Tom...
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