Why not? Well, #6 is only rated for 65A max, so I guess that's a pretty good reason why not. I think you'd get spanked over it.

 

Don't know canadian rules but do you have a next size breaker rule. Also is NM cable rated 60C as it is in the US.

 

That's a good point. Yes, we have a similar rule, and yes it would allow 70A. However, that just seems like the kind of thing that an inspector would nail you for. I'd definitely ask first.

Our underground-rated #6 is rated 60C (max 55A), but the rest of it that you normally see is all rated 90C. 75C and 90C have the same ampacity (65A) so that isn't an issue.

 

Table 310.15(B)(16) (formerly Table 310.16) Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000
Volts, 60°C Through 90°C (140°F Through 194°F), Not More Than Three Current-Carrying Conductors in Raceway, Cable, or​

Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F)*

 

read nec sec. 215.2 (A) (1), last sentence. The minimum feeder-cuircuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less then the noncontinuous load plus 125 percent of the continuous load. so if you were completely loading the 70 amp subpanel with a continuos load, 70 times 1.25= 87.5 amps, or even half the load being continuous at 78.5 amps, you would still be over. One can't just use t310.16.
0

 

They are Canadian, none of that applies.

 

I do industrial. I've never used NM in a professional capacity. That having been said, I see nothing in our code book that indicates that NM is treated any differently than any other non-flexible multi-conductor cable.

 

Where are all the canadians on this one????

 

We should always go by the code but the bottom line is that there is a good safety factor in what the code wishes. I do not deviate but some times people wonder what will a conductor take. A #12 cu in free air will conduct 200 amps before starting to melt. The insulation is what we are protecting and therefore the premises.

 

We should always go by the code but the bottom line is that there is a good safety factor in what the code wishes. I do not deviate but some times people wonder what will a conductor take. A #12 cu in free air will conduct 200 amps before starting to melt. The insulation is what we are protecting and therefore the premises.

I'll say Amen to that brother.

 

LOL-- I got my Mikey's confused....:laughing:

 

What would be the purpose of rating #6 at 65 amps if you can out a load of 69 or 70 amps.

 

Hey all, first post for me. I believe the CEC is 14-104 in conjuction with table 13.

I think this is the code that Mike 586 mentioned on the previous page.

 

It is, but 8-104(1) overrides T13. Check the references on T2.

 

Yup! you're right!