Welder Extension Cord

[dstig1]

Actually Mike, Lightnsound is right. Ampacity is current carrying capacity, irrespective of voltage and it is based on the wire size. This is unrelated to power, which is what you are describing. You can get more power through the same size wire by going to higher voltages, which is why bigger tools run on 220V instead of 110v, for example. But a 10ga wire is rated for 30A (per NEC), at 110 or at 220 or any other voltage for that matter.

 

[Lightnsound]

A watt (=volts x amps) is always a watt.
Otherwise how could you get 180 amps from a machine on a 40 amp breaker???
MikeD74T

Thanks to dstig for clarifying what I was saying.

Mike, the power formula in your post explains how you get 180 amps out of a 40 amp breaker. Your welder draws current from the 240 volt supply, but then bucks the voltage down to somewhere around 20 volts (give or take, for a mig welder). Your formula shows that 40 amps at 240 volts is 9600 watts. 180 amps at 20 volts is only 3600 watts which would draw 15 amps from the 240V power supply. These numbers aren't really true due to inherent inefficiencies in the machine, and the current drawn by the control circuit, fan, and wire feeder motor, but it's pretty close. So I think we are definitely on the same page.

 

[MikeD74T]

lightnsound & dstig1, Thank you both for prompting me to learn something new. A little research confirmed, and helped me to understand, that an amp is a finite amount of power & a watt is the rate of work done by one amp volt. An amp is in fact an amp, and ampacity is finite despite voltage.

When these wire size discussions come up what often gets lost is the actual demand of the electrical device vs the reason why a certain wire size is needed to support that demand over various distances, and how distance induced voltage drop increases actual demand. Even in this thread it's disputed whether the cord needs to be big enough to max out the breaker or the breaker needs to be big enough to max out the cord. In most cases neither is absolutely true.

I'm still curious to know what JJ's chart comes from. MikeD74T

 

[J_J]

Just another chart for extension cables.

Extension cord - Wikipedia, the free encyclopedia

I am still confused about the wiring from inside the house to an outside sub panel.

Would someone compute the gage wire from the circuit breaker panel in side the house, to the outside of the house about 30 ft, then 75 ft run to a sub panel for my plasma cutter using 240 V, and the machine drawing 46 A. The input gage for the plasma cutter is 10 ft of #8. What would be the circuit breaker size on the inside panel, and the sub panel. If I made up an extension cord of 50 ft, what gage wire should it have .

Would the gage wire be different if I used 4 single stranded inside conduit, or direct burial?

ProCut-55 plasma cutter


TECHNICAL SPECIFICATIONS - PRO-CUT 55
INPUT RATINGS
Single Phase Input Input Currents Rated Output Amps
Voltage and Hertz

208/1/60 Input-60A , 55A Output
230/1/60 Input-55A , 55A Output


RECOMMENDED INPUT WIRE AND FUSE SIZES
For all plasma cutting applications based on U.S. National Electrical Code
Ambient Temperature 30ｰC or Less
AC Input Voltage Fuse (Super Lag) Type 75ｰC
at Circuit Breaker Copper Wire in Conduit AWG
60 Hertz (Delay Type) (IEC) Sizes

2 Input Supply Wires 1 Ground Wire


230VAC Single Phase 70 Amps #8 (8.4mm2
) #10 (5.3mm2

 

[jake98]

I thought my new plasma cutter was going to be the straw that broke the 50 amp breaker's back. Shop is 150' away on buried 6 wire. The 7hp compressor starts while cutting no problem. I've only cut up to 40 amps so far, and I doubt the compressor is really 7 hp, but that's what it says. I'm using another 50' of 8 wire romex for the extension cord to the cutter, too. Got 6 150 w bulbs going, and a stereo, usually.

 

[deereman75]

I thought my new plasma cutter was going to be the straw that broke the 50 amp breaker's back. Shop is 150' away on buried 6 wire. The 7hp compressor starts while cutting no problem. I've only cut up to 40 amps so far, and I doubt the compressor is really 7 hp, but that's what it says. I'm using another 50' of 8 wire romex for the extension cord to the cutter, too. Got 6 150 w bulbs going, and a stereo, usually.

how many cfm does your compressor put out, my 3 real hp compressor puts out 12.1 cfm, I have seen "6.5 hp" compressors that only put out 11.

 

[jake98]

how many cfm does your compressor put out, my 3 real hp compressor puts out 12.1 cfm, I have seen "6.5 hp" compressors that only put out 11.

I believe it says 13 point something. The motor is 1/3 the size of a real 3 hp..

 

[JB4310]

I am still confused about the wiring from inside the house to an outside sub panel.

Would someone compute the gage wire from the circuit breaker panel in side the house, to the outside of the house about 30 ft, then 75 ft run to a sub panel for my plasma cutter using 240 V, and the machine drawing 46 A. The input gage for the plasma cutter is 10 ft of #8. What would be the circuit breaker size on the inside panel, and the sub panel. If I made up an extension cord of 50 ft, what gage wire should it have .

No computing here, more guessing, but sounds like you would need a minimum of a 50 amp circuit from the house to the shop (probably would want more to run other things) and a 50 amp breaker at the sub panel I THINK at those distances you would be good with 6 gauge wire the whole way.

As far as the extension cord goes, if the machine has an 8ga cord now, then at 50 feet sounds like you would need to step it up to 6ga.

But as this thread has proven, much of what us amateurs thought was fact is up for debate???

Here's a picture that demonstrates the difference in size between the supply cord on my welder which is only 12/3 and the extension cord I made out of 6/4. I used the same 6/4 wire to make up these plug configuration adaptors, the 12/3 is what looks like a little string next to them.

JB

 

[jake98]

I think I'd rather drop a piece of steel on the thinner wire. Should make less noise..

 

[Short Game]

The welder is the plug on the left. Interesting that the required 50 amp outlet serves the 12/3 cord, while those 30 amp range and dryer outlets often get 6/3 cords plugged into them.