#6 SEU cable - 40 or 50 amps?

[jeff48356]

I see a lot of kitchen ranges wired with #6 SEU cable. These are older ones, back when only 3 conductors were allowed. Are these supposed to be protected with a 40A or 50A breaker. 310.15 table says 40A if 60 deg. C, or 50A if 75 deg. C. Which one applies?

 

[GerryB]

I see a lot of kitchen ranges wired with #6 SEU cable. These are older ones, back when only 3 conductors were allowed. Are these supposed to be protected with a 40A or 50A breaker. 310.15 table says 40A if 60 deg. C, or 50A if 75 deg. C. Which one applies?

Those old cables I've seen were always copper, so 55a or 65a.

 

[jeff48356]

Those old cables I've seen were always copper, so 55a or 65a.

These are actually aluminum.

 

[LarryFine]

Three conductors was never a "requirement," more of an allowance. The requirements were either an insulated neutral or SE cable, and fed from the panel containing the service main, not from a sub-panel. Mobile homes have required the 4-wire circuit for decades longer.

I'd say the 60 degree number, unless you have evidence of a higher temperature rating to the contrary. I don't believe a typical range will ever trip a 40a breaker, though.

Those old cables I've seen were always copper, so 55a or 65a.

These are actually aluminum.

You're both right. Some were copper, some were nickel-plated copper, and some were aluminum.

Jeff, with aluminum, I think you're limited to the 40a breaker anyway.