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Forum topic by DocK16 posted 03-28-2011 06:11 AM 1431 views 0 times favorited 7 replies Add to Favorites Watch
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DocK16

1178 posts in 3553 days


03-28-2011 06:11 AM

Topic tags/keywords: electrical

I need to run an outlet so I can move my planer to the other side of the shop. It is a 5 hp motor, tag on the motor says it draws 240 volts at 19 amps. The outlet will be about 35 feet from the breaker box. I have some wire marked 12 AWG , 300 volts. Question is; is this heavy enough to carry the load or am I in danger of burning the motor up or starting a fire?

-- Common sense is so rare anymore when you do see it, it looks like pure genius.


7 replies so far

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crank49

3981 posts in 2437 days


#1 posted 03-28-2011 07:40 AM

The good news is that by the numbers the 12 ga wire is good for 20 amps.
The bad news is that a 5 hp motor will pull way more than 19 amps when starting.
You might get by with a special breaker designed for motor loads and 20 amps, but not likely.
Bottom line, you really need at least a 30 amp breaker and 10-3 awg wire to run a 5 hp motor.
In any case, the breaker must be sized to protect the wire and satisfy the local code requirements.
14 awg = 15 amp
12 awg = 20 amp
10 awg = 30 amp
8 awg = 45 amp
6 awg = 60 amp

I’m assuming your 5 hp motor is an induction motor, probably with capacitor start, and not a built in direct drive, universal type motor. Universal wound motors are way over rated by manufacturers and confuse the whole issue of hp v.s. amps. For example a shop vac with a 6 hp rating that runs on 120 volts and 15 amps. Pure BS.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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TopamaxSurvivor

17674 posts in 3142 days


#2 posted 03-28-2011 07:52 AM

You need to use at least number 10 as crank49 says. What size breaker are you using? For a dedicated motor circuit, you can over size the breaker is need be for starting. I would doubt if that would be necessary starting a planer. Might be necessary starting a compressor ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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TopamaxSurvivor

17674 posts in 3142 days


#3 posted 03-28-2011 07:55 AM

BTW, that 300 volt wire is most likely for some kind of low voltage circuit. What else does it say on it? Any lettering like CL2 or CL3? All building wire for line voltage wiring is 600 volt rated.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Strider_Greybeard's profile

Strider_Greybeard

4 posts in 3193 days


#4 posted 03-28-2011 02:30 PM

Crank49 is right on the money.
Breakers should be sized for 125% of the load. 19×1.25 = 23.75
A 30 Amp CB with 10 Ga wire.

-- Allen, West Virginia - Never give up, Never surrender

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ScottN

261 posts in 2146 days


#5 posted 03-28-2011 02:45 PM

-- New Auburn,WI

View DocK16's profile

DocK16

1178 posts in 3553 days


#6 posted 04-02-2011 03:58 PM

Thanks all. Now have to figure out if I want to do my taxes this weekend or rewire the shop.

-- Common sense is so rare anymore when you do see it, it looks like pure genius.

View bubinga's profile

bubinga

861 posts in 2134 days


#7 posted 04-02-2011 04:22 PM

I use #10 wire for 2,and 3hp motors

-- E J ------- Always Keep a Firm Grip on Your Tool

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