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!
I doubt very much that this would meet Code. First of all, you can't just pass the cable
through the knockout hole -- for the protection of the cable and the connections, Code
requires some sort of fitting on the hole (e.g. a cable clamp aka "Romex connector") which
secures the cable to the box. And I can't imagine that any fitting which would fit a 1/2"
knockout is listed for use with anything as large as 6-3; for example, the Romex connectors
used with 1/2" knockouts are listed for 14-2 through 10-3.
Does the panel have any vacant 1" knockouts? Or can you ream the 1/2" hole to 3/4"?
On Monday, July 21, 2014 7:17:12 PM UTC-4, Doug Miller wrote:
Aside from that, does he really need #6 for an AC? Presumbably a home AC?
I have a 5 ton, which I believe is the largest made and it's rated for #8. I
wonder if he's sizing based on breaker, instead of sizing based on the
install instructions and eqpt rating. Meaning I have a 50 amp breaker on
my 8 gauge, 5 ton and it's to code because it's a motor load, not an oven.
On Mon, 21 Jul 2014 15:30:28 -0700 (PDT), firstname.lastname@example.org wrote:
Can you get the 6-3 cable through the required cable connector, is
the big question. If you can fit the 6-3 into the connector that
threads into the 1/2" knockout, you are gold. If not you will need a
knockout punch to enlarge the hole to 3/4" size (Greenlee punch)
I assume you mean a reamer - which leaves all kinds of conductive
swarf all through the panel. The only RIGHT way to do it is with a
"knoclut punch" - aften referred to by the most common brand - a
"greenlee punch" Any electrician worth his salt will have one. All you
get that way is a metal ring.
On 7/21/2014 8:31 PM, email@example.com wrote:
HF sells step bits which can be used to enlarge
the hole. Of course, you need a shopvac in action
at the same time to catch the chips.
Instead of a rimmer, use a knoclut punch. Amazing,
one good misssspelled word desserves anothher.
Christopher A. Young
Learn about Jesus
Whether he needs AWG-6 or AWG-8 is not really relevant -- neither one is listed for use with
any Romex connector or clamp that I'm aware of which will fit in a 1/2" knockout.
Another question for the OP: do you really need 6-3 (or 8-3, as the case may be) for an air
conditioner? If it's central AC, it's almost surely a pure 240V load, and 2-conductor cable will do
-- and if it's a window AC, 10-3 is almost surely sufficient.
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?
WRONG. The big question is whether the required cable connector is listed for use with 6-3
cable. If the connector is not listed for use with 6-3 cable, it's a Code violation to use it for
that, whether the cable fits or not.
On Tue, 22 Jul 2014 01:14:05 +0000 (UTC), Doug Miller
Well, you show me a romex connector that will take a 6/3 cable that
isn't listed for use with 6/3 and you may have a point. The POINT is,
there is no romex connector that WILL accept a 6/3 - listed or not..
Hi, I'm the OP.
Yes, the mini split a/c system specs explicitly call for a 50amp breaker and #6 AWG (although I shudder to think that it'll actually use that much, with a 16 SEER).
I think I answered my own question by finding several "conduit fill charts" online that say 1/2" conduit can only have 2 #6 wires, so rules are there to keep me safe and I'm fine with that.
I also failed to notice one last 3/4" knock-out, so I'll be using that one.
Many thanks to all the good technical solutions and suggestions!
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