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.

 

[JB4310]

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 will likely get 6/3 plugs in them.

I'm trying to figure out how you pigtailed twelve 6ga wires in there???

I know you mentioned soldering, but that's alot of wires in that first (center) box.

JB.

 

[Short Game]

I'm trying to figure out how you pigtailed twelve 6ga wires in there???

I know you mentioned soldering, but that's alot of wires in that first (center) box.

JB.

That one is done with 8, and even that wasn't all that easy. When I do that, I merge the wires right at the connectors and remove just enough strands from each until the total will fit, then solder the lot before clamping. That outlet set was definitely a cluster tuck.

To tell the truth, I can't remember exactly how I joined all three back behind the outlets where I carved into the 1.5" wood backing. I'm NOT taking it back apart to see what I did! :laughing:

I built that thing not 6 months ago, and already the memory is gone. I'm okay with it, knowing how **** I get about things I build. No one can work with me. It's that bad. :ashamed:

 

[dstig1]

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

JJ, if I was doing it, and the actual draw of the unit was 46a, I would use a 50A breaker. Welders don't have the same issue of startup current like motors do, so you really don't need much cushion. 6ga Cu would be the safe way to wire that.

But you are confusing the issue more with your subpanel. The purpose of a subpanel is to get a panel closer to a bunch of circuits so you don't have to run a bunch of long "home runs" back to the main panel, but just run one bigger wire to the panel, then the circuit runs are a lot shorter. If you are running a subpanel for this one item, you could probably just run an outlet instead, unless you are planning on future expansion. If that is the case, then a 100A subpanel is a decent size for a shop, IMHO. It gives you some room to work with.

An 8ga extension cord 50' long should be fine for your use, but if you wanted to be safer, you could go up to 6ga. If in doubt, going bigger never hurts.

If you have an electrical inspector in your area, the easiest thing to do is call them during business hours (usually 1st thing in the AM they will be in the office) and ask. You don't need to give your name. Then you will know it will meet the local requirements.

Oh - one thing that will help is to look for a voltage drop calculator online. There are a bunch of them but if you type voltage drop calculator into Google, you will get several good choices at the top. You want to minimze the drop due to resistance in long wire runs, so input your info there and find out if it is good enough or not. People vary in what allowable drop they like but 3% is a decent rule. You can go lower if you are using more sensitive equipment or larger loads.

 

[ToolBoxTavern]

I am sure you will be fine. My outdated code book says 8 gauge is for up to 60 amps. I was actually going to get 20 feet of 6 or 8 gauge for my welders cord, but because of a mistake by the new guy at the cable store, we got 25 feet of 4 gauge for like $40-$50. If I had to pay the full price for the cable, no way would I use 4 gauge, 6 at the most. (this thing is HEAVY)

Thanx

 

[ToolBoxTavern]

Welder circuits and extension cords can be Derated a little bit due to the duty cycle of welders, meaning they are not drawing current constantly. Your #8 cord is perfect. Just look at the Cord that came attached to the welder, it's probably #10.

Thanx for the reply. I have seen guys use a lot lighter wire which I think is crazy, but I figured I was in the ball park here.

 

[ToolBoxTavern]

ToolBoxTavern,

You only have 33 A input current at 208 V with a 40 A cutting ability.

http://www.hobartwelders.com/pdf/spec_sheets/AirForce_700i.pdf

Wire Size Calculator

This calculator says that if using a 50 ft cord, and 33 input amps at 208 V, the wire size required computes at #14, single phase , copper wire.

Thanx JJ. Greatly appreciative for your time.

 

[ToolBoxTavern]

Well something is odd, I thought it was generaly accepetd 14 gauge wire is good for 15 amp circuits, 12 ga for 20 amp, 10 ga for 30 amp, 8 ga for 40 amp, and 6 ga for 50 amps.

I'm sure these are not exact ratings, but for wiring residential circuits I thought this was the standard ???

JB

Sounds like a good reference point.

 

[ToolBoxTavern]

In my state if you wire up a 50amp breaker to #8 wire you'll fail inspection.
All of my 50amp extension cords are #6 three conductor with ground.
Just saying.

I hear ya.

 

[ToolBoxTavern]

I talked to the a Lincoln rep about the size wire on my Pro Cut-55, and he says and I agree that #8 is the correct wire to use. He also said to use an extension cord of the same wire size as the cord on the plasma cutter. I can also use my Ranger 8 and the Miller 10 KW Gen/welder with the plasma cutter.

Some of you can get away with some things, some of the time, but you can not get away with all things forever.

It's your machine and wire, so use what you have for the time being until you get it right.

There might be a difference whether the wire is 4-single stranded wires in a 1 in/1 1/4 in conduit, as compared to a wrapped set of 4 wires encased in a rubber sheath. [ extension cord ]

Interesting.

 

[ToolBoxTavern]

And heres a final note to really throw you for a loop. Manufacturers don't have to follow the NEC. Thats why you'll see a limp fixture with 22 Gage wire... real micro fine wire ... that plugs into a 15 or 20 amp socket. That wire is probably only rated at 5 amps, but they get away with it. Ive seen 5 HP air compressors with #12 pigtails /.... WAY undersized but thats how they were shipped.

If you look inside an electric water heater you'll find that the innerds are wired in #12 wire HOWEVER electricians are required to wire up to it with #10 (larger ) wire. Makes no sense at all.

Public utilities are also immune from the NEC. I reciently wired a 400 amp comercial building with an overhead service. I had to run Parallel 350MCM COPPER feeders up 20' of 3" rigid riser pole thru the weatherhead. The utility company dropped a wire about the size of a #6 aluminum wire to connect their side of things. According to the code book, that wire ig good from the range of 40 - 60 amps, but there powering up a 400 amp commercial shop with it, Their lineman just shook his head and told me if it proves too small they'll up-size it later on. No codes and no inspection on their end.

I've seen the same things.