new kitchen

For my new kitchen i'll be laying all new circuits - and bringing to the breaker box. i'll be running through rigid conduit thru the garage.

If i run 1inch rigid conduit, will that be enough for

5 15A 120v circuits on 12AWG
1 30A 240V circuit on 6AWG

Also - i'm pretty sure that i can use a single neutral for the 120v circuits thru that rigid pipe - is that correct?

If so, then I'll have
7 12AWG wires (5 hot, 1 neutral, 1 gnd)
3 6AWG wires (2 hot, 1 gnd)

...going through the 1 inch pipe. I tried to make sense of the NEC 2002 code for diameters, but i confess i was quite lost!

Tony

 

Well,,,, not all conduit is rigid. You probably want emt if it isnt buried. But,,,,, you have some homework here before tackling a kitchen project. You would need a minimum of 3 neutral wires for the 12 circuits but,,,, again in this case I (and I think Iwill get some back up here) it is a bad idea. Bite the bullet and run a neutral for each one. The 30 A circuit needs only a number 10 wire. Sometimes if the run is really long,,, 75 or 100 ft or more we might go to number 8. I didnt calculate it but with number 10 all that will run in one inch I am sure.

 

If possible, I suggest using the 1" raceway for a 3-conductor "feeder" which supplies a panel as near as possible to the outlets being connected. You can fit three #4 conductors in a 1" raceway which gives a 100 amp feeder and I would include an Green Equiptment Grounding conductor.This arrangment provides space for future circuits or other circuits you may find that you need as you progress with your project.----Good Luck!!!!

 

Read up on ampacity derating. You won't like what you find. After derating these wires, you won't be able to use a 20-amp breaker on 12-gauge wire. So to get a 20-amp circuit, you'll need to move up to at least 10-gauge wire. For proper heat dissipation, you are not going to want to group that many wires in one raceway.

And has been pointed out, it would be extremely dangerous and a very serious code violation to use one neutral for five circuits. That one neutral wire would likely melt or catch fire.

 

So what's the correct approach then. I've been reading about derating the wires when they are bundled (seems to be an issue of heat buildup reducing the carrying capacity of wire, correct?)

Clearaly my 5 or so 120v circuits on 12awg and my 240v on 10awg aren't going to work well in a conduit together.

The problem is that these circuits will pop out from my kitchen onto my garage wall, where they will be run in EMT to the breaker box, a distance of about 35 feet. But it's too many wires to run in 1" conduit.

PATTBAA's suggestion was to use a feeder box - is this a better way to avoid dealing with the derating issue? Using this method I would only be passing 4 conductors to my box - 2 hot, 1 neutral, 1 equipment ground.

I know there's a million ways to do this stuff, just looking for a good safe approach.

Tony

 

Using a sub-panel is ok, but at 35 ft, I'd look into cost comparing it
to home running, possibly through 3 conduits, half of your 20A circuits in two, your 30 A circuit in the third (it will have a neutral as well, as those convetion ovens are 120/240 appliances, and use a 4 prong dryer outlet.)

 

Don't worry about derating in this case. You say you want 5 circuits. Pull in 5 hots and 3 whites and a green ground. Use #12 thhn in a 3/4 inch EMT conduit. Make sure that the 2 circuits that are sharring one nuetral fall on different legs. Ex: Circuit 1 can and 3 can share a nuetral, but circuit 1 and 2 can not. They must be on different legs. Derating factor determins the ampacity of the wire. #12 thhn is rated for 30 amps when there is less than 3 current carrying conductors. The derating factor is 80% for 4-6 current carrying conductors and 70% for 7-9. You fall under the 80% because sharring nuetrals is not considered current carrying. 80% of 30amps is 24. Even if you counted all wires as CCC's you still fall under the 70% and it comes to 21 amps to be protected by a 20 amp breaker.