Art Greenberg wrote:
On Fri, 03 Aug 2007 16:54:22 GMT, Doug Miller wrote:
In article , Ignoramus2331 wrote:

thinwall, rigid, 12 gauge THHN
Code permits up to 9 (!!) 12AWG THHN conductors in 1/2" thinwall ("electrical
metallic tubing" or EMT), so you're perfectly good with three or four. Even
though Code permits using the conduit as the equipment grounding conductor, I
prefer to pull a separate wire when possible.

Nine would be pretty tough to pull, though. g

And seriously derated in ampacity.


That is an interesting point.

Say you have 4 circuits - hot and neutral - plus a ground wire - 9 wires
all #12.

The ground wire does not count for derating.

For 8 wires (up to 9 wires) the derating is 70%.

The ampacity of THHN is 30A (but it must in general be protected at 20A).

70% of 30A is 21A. The 4 circuits may be used at 20A.

THHN is wonderful stuff.

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bud--