Power mains question: wire gauge

I would, since the starting current is much higher.

Cant hurt. It would definitely help, in fact. multiple #14s to make each #10 would work better, keeping each segment electrically separated except at the nodes, giving a sort of Litz effect. At that gauge, you can get SPC too (Silver Plated Copper), reducing ohms per foot without increasing gauge above #10.

And you want a #12 return run for ground fault carriage too. A single piece would pop a breaker.

"DaveC"

Such a motor normally draws around 3 amps.

... Phil

#12 is 1.6 mohms/foot. That's 0.32 ohms total. The short-circuit current from 220 volts is almost 700 amps. A half horse is only around

ance

make

considered what the skin deepth at 60Hz is?....

-Lasse

Up to 4.9 Amps, according to the 2011 NEC (Table 430.248). And that's all you have to provide in terms of feeder/branch circuit ampacity.

Maybe the decimal placement error is on the amps. 1.5 instead of 15. That math works too, btw. 220 * 1.5 = 330 or ~ .5 HP

There is s thing called "voltage drop". Voltage will drop in a wire running a long distance, sometimes so much, the device at the end will not operate!

The amount of voltage drop depends on the voltage, the type of metal used for the wire (copper / aluminum), the wire size, and the load in amperage at the end of that wire.

The internet has made this easy for you. Just search google.com for the words...

Voltage Drop Calculator

If your motor is about 80% efficient, then at full load it'll be taking about 466 watts from the mains, which is about 2.1A.

Until the motor or compressor is replaced with a larger unit. Then all bets are off. It's cheaper to do it right the first time. You could even put a small breaker box by the compressor & run AWG 6 to it, to power other tools, as needed without starting from scratch.

That's a good idea. I'll talk it over with the owner.

But for now I want to settle on what size conductor to use if it's just to supply this one compressor.

Thanks.

nce

The NEC motor tables for 1/2 HP single phase at 230 specify FLA of 4.9A and LRA of about 30A. NEC also recommends sizing branch line for no more than

Thanks for your reply.

Sorry you did all that calculation on the wrong HP rating. (See my post earlier today.) Motor is actually rated 3.1 HP.

Thanks.

If it's 1/2HP, now, it's unlikely to grow to >5HP.

Run several #12s, instead, when needed. It's cheaper.

Pull additional #12s in the future? I've had bad experience pulling additional conductors in a conduit with existing conductors.

If I misunderstand your statement, please try again. ;-)

Thanks.

No. A bundle of a few 12s will make a nice oversized #10. The finished 'wire' will be stronger and more flexible too.

Of course, the return has to match. So you pull all 7 at once.

Two sets of 3 #12s and one #12 fault return. Seven wires.

I don't see earlier post. At any rate, the FLA for 3HP is 17A and LRA is 10

Strictly against code!

Conduit?