Question on wire size for 30a

enblethen wrote:
THHN/THWN would need to be installed in conduit.
#8 Type NM normally is three conductor with ground.
If this is all inside the house, you may just install 10/2 with ground and live with it. You will most likely never come close to a full 30 amp load.
You would just need to watch using heavy items like air/cond.

You shouldn't need to "watch" using heavy items. Not every one is going to "watch" and that's how things get burned down. Let enough heavy line carry the load properly, and let the circuit breaker do it's job.

THHN/THWN would need to be installed in conduit.
#8 Type NM normally is three conductor with ground.
If this is all inside the house, you may just install 10/2 with ground and live with it. You will most likely never come close to a full 30 amp load.
You would just need to watch using heavy items like air/cond.

gbopp wrote:

MEXICOWANDERER wrote:
Lots of factors involved.

Penny-wise, dollar idiocy. I don't have enough money to chase nickels with dollars.

Well said! What gauge wire would you use?

At a minimum, since it's so close to max of 50 feet or more, I would run THHN 8 gauge. 8 gauge Romex is only rated 40 amps, due to the plastic thermal jacket it's molded into, that makes it only easier to pull, retaining too much heat.

MEXICOWANDERER wrote:
Lots of factors involved.

Penny-wise, dollar idiocy. I don't have enough money to chase nickels with dollars.

Well said! What gauge wire would you use?

enblethen wrote:
Technically no, realistically yes. You would connect the black wire to one of the breaker output and the white wire to neutral. The vacant output would have no connection.
I would not recommend doing it. I would get a single pole breaker and do it right.

I agree. But I know it has been done.

Lots of factors involved

#1: Do not ---- off your homeowner's insurance by violating LOCAL electrical code.

#2: Got a fat wallet? NEC code for MOTOR START circuits is a tad different.

#3: Like NinerBikes pointed out. If you refuse to use common sense, use #10 AWG, connect a voltmeter at the load, have your accessories going and then high-head start your AC. SURPRISE! The bigger the start voltage drop the bigger the TWANG that entire circuit is going to get when the motor cap start disengages. This is not E=MC2 theory it is from experience and an oscilloscope.

#4 NEC does NOT COVER every contingency and it does not cover every load variance. The NEC covers their own ---, and that of manufacturers, and underwriters. The NEC does not cover such inconsequential facts such as length of service life AT THE LOAD. That's YOUR WALLET not theirs.

I used a house as an umbilical connector with sixty feet of provided extension cord BRAND NEW cord, my 30-amp socket. After suffering 20-volt drops for 5-days when the roof air cycled (100F/90F) the 10 gauge duplex CAUGHT FIRE a foot or so distant from the rig connector. I assembled stuff myself. The CU to trailer socket connections used U-shaped fork connections which were SOLDERED. The fire did not hurt the socket but it did discolor the terminations.

An "X" ampere load may not be "X" at all. Add your rig hotel load to a 3-times amperage draw factor of a roof air high head starting amperage. Now does THAT meet otherwise misinterpreted NEC electrical code. Of course not.

Connectors and connections degrade over time. After say 5 years will those terminations have the SAME ampacity as brand-new terminations? Of course not.

Penny-wise, dollar idiocy. I don't have enough money to chase nickels with dollars.

Lynnmor wrote:
When counting the number of feet for voltage drop, you need to include the wire from the panel to the outlet, then the length of the power cord and also include the wire inside the RV to the highest load. You are probably over 100 feet total.

Good point, thanks.

When counting the number of feet for voltage drop, you need to include the wire from the panel to the outlet, then the length of the power cord and also include the wire inside the RV to the highest load. You are probably over 100 feet total.

For runs under 50 feet, 10 gauge wire may be rated for a 30 amp load, but for continuous load, it is derated to 80% of it's value, or 24 amps. This is important to factor in if you ever decide to plug in an Electric car with an EVSE to recharge the car... your circuit is only rated 24 amps. You might want to think about future proofing your installation.

enblethen wrote:
Technically no, realistically yes. You would connect the black wire to one of the breaker output and the white wire to neutral. The vacant output would have no connection.
I would not recommend doing it. I would get a single pole breaker and do it right.

Got it, thanks.