On Tuesday, July 22, 2014 6:43:07 AM UTC-4, Stormin Mormon wrote:
On 7/21/2014 6:30 PM, wrote:

Hi,

I'm running a 6-3 Romex NM-B with ground for my new

air conditioner system.

My main panel doesn't seem to have any spare

(unoccupied) 3/4" size punch outs left; but there

is a 1/2" punch out. It is possible for me to fit

this 6-3 with ground in there, but does anyone know

whether this is prohibited by the NEC?

All advice (and NEC references) appreciated!

Regards,

Theodore.



On a practical note, I'd be sure to have a Romex

connector



http://www.contractcleanersupplies.c...-connector.jpg

in the punch out. Just to run the wire through the

hole leaves the risk of the panel metal wearing

through the insulation and causing a short.



How many tons of cooling? I remember using 10 AWG

for 2 1/2 ton system one time.



I think Gfre might be on to something when he suggested it might
also have resistance electric heat and maybe that's why the need
for #6. If the OP gives the make and model we could probably find
the specs and install intructions and I'd like to take a look.
I'm still skeptical that a mini-split could really need #6. As I said,
my 5 ton central AC uses #8, but being AC only, it doesn't have any
resistance heat.