Friction loss in an extension cord?

[SoCal Dave]

I have a Lincoln 125 wire feed welder with flux core wire.  I need to use an extension cord to get to my welding job on a barn.  I was looking at Harbor Freight extension cords, specifically, the 100ft 10 guage which would be the perfect length.   I'm concerned about the friction lost in 100 feet. I know it's not friction loss but I don't know the correct electrical term. I also figure this might be the right kind of harbor freight item to purchase.    

[Frosty]

Yeah, it's resistance. Wish I could be more help but that's about it. Well, there are charts listing power loss according to distance over wire gauge. Uh, I think that's all I know outside of an electrician's number.

 

Frosty The Lucky.

[Geoff Keyes]

Resistance loss is what you're looking for.  It might be enough, but you'll know if it trips the breaker.  It's a long run, so I expect that you are right on the edge.

 

Geoff

[Frozenforge]

Usually the instructions for the welder will have extension cord specs. The issue will be the amount of voltage drop due to the resistance. As the voltage drops tha amperage goes up trying to maintain the same amount of watts. As the amps go up the wire heats up causing either the welder to overheat or the extension cord to overheat.

This is why voltages for large equipment are either 240 or 480, it lowers the amperage to get the same amount of power (watts).

[DSW]

What you are describing is typically called voltage drop due to the resistance of the cord. Typically the answer is to go to a larger cord like you have to reduce the resistance and lower the drop in voltage that occurs. 10 ga over 100 foot shouldn't be an issue, but I have no idea what the HF cords are like. Understand that even with a heavy cord like a 10 ga one, you are going to have some voltage drop and this will effect the ability of that small machine to produce it's maximum output. Reduce your max thickness accordingly.

 

 

I recently this summer ran into a very clear cut case of this happening. All of a sudden my air compressor stopped wanting to run when it tried to kick back on after the pressure dropped. All it would do is try to start, stall and then hum, so we'd quick shut it down. When drained, it would fire up no problem.  Same thing occured with my backup unit. Some times it would seem to work just fine, then suddenly at other times it wouldn't. It took me a bit to figure out what was going on. Turns out the helper was playing musical cords when he needed to plug a different tool in because if he plugged into the power strip on the other cord, he'd trip the onboard breaker. However he wasn't paying attention to what cords he unplugged and pluged back in to which extension cords. It turned out when he unplugged the air compressor from my 2 10 ga 100'  cords and plugged them into the customers 2 14 ga 100' cords, the compressor couldn't draw enough juice over that distance to run properly and would stall. The lite gauge cord was there mostly to run a small light and the battery chargers, not try and power big draw tools like the air compressor and saws.

[Glenn]

It is NOT just the 100 foot extension cord you need to be concerned about, it is ALL the electrical connections from the load clear back to the electrical panel.  If you have a 10 ga extension cord attached to 12 ga wiring, with a 14 ga multi-outlet box somewhere on the line, you are running 14 ga for the drop. Take the multi-outlet box out and you would only be running 12 ga for the drop. It is the weak link sort of thing.  You also need to check the size of the breaker to be sure it is both large enough to give the service you need and small enough to trip when needed.

[SoCal Dave]

Assuming that I'm working on a 15 amp plug on the extension cord and the wire from the outlet box to the breaker is adequate and the panel breaker is 15 amp, will I have a significant resistance loss to enable me to weld a hinge on a stall door? What if I went to an 8 guage extension cord.   Would that make a difference compared to a 10 guage?    

[DSW]

Not enough to matter, and finding an 8 ga extension cord designed for 110v power isn't easy. largest I typically see is 10 ga, and usually designed for large draw tools over longer distances. The 8 ga cords I see are usually 30 amp 230v ones for gensets to aux hook ups for homes. My guess is with a 10 ga cord it will be the 15 amp circuit that will be your biggest limitation.

 

 

If you are running of a 15 amp circuit you are already dropping the available power down. If you read the manual on the vast majority of these little machines, they rate them on a 20 amp dedicated circuit.  Some need even more power to reach maximum output, something like 25 amps of 115v input ( which to me is sort of pointless since the idea of a 115v machine is to be able to use it on "standard" circuits...) to obtain the max suggested settings. That means nothing else plugged into the circuit except the welder. Many don't even suggest using an extension cord, even if they do list suggested cord sizes if you actually read what hey have printed.

 

As far if it's "good enough" to weld a hinge on a stall door, I'd really need a lot more information. If we are talking about a hinge to light 16 ga tube, then I'm sure it has plenty of power. If we are talking about welding a heavy 1/4" strap hinge to heavy steel, then possibly not. At that point even under perfect conditions the material is really too heavy for that small machine, so the welds will be marginal at best. How good a welder you are and how much length of weld at that point would really be the deciding factor.

 

My guess is you are over thinking this a bit.  If you have a 10 ga extension cord, then by all means use it. It will reduce the volyage drop as much as is reasonably possible. However 10 ga 100' cords are not cheap, and they are quite heavy. I have two, and usually I use them only when I know I will have no choice but to go a long distance from my power source to the work and want to limit voltage drop if possible. They are just way too heavy to lug around.  99% of the time all I'm using is top quality 100' 12 ga extension cords with no issues. As far as welding up the hinges, tough call. I'm tempted to say you are probably OK, but I can't say for  sure with out more info on the details of the materials, and your skills as a welder. I wouldn't worry about my welds on what I have at one customers horse barn if I had to use my small 110v mig. I will admit a horse will tear stuff up if it gets cranky, and I've seen plenty of cold welds made with small 110v migs that wouldn't stand up to 1000lbs of horse bashing on something.

[yahoo2]

 in copper braid roughly 0.098 Ohms plus 0.02 ohms for the extra plug in the line. So you are looking at around 12% loss minimum over what you have back at the wall socket. 8 gauge will be 0.063 Ohms (wire only) for 100 ft. 12 gauge 0.15 Ohms for 100ft

 

obviously a 10 foot cord would have a 3% loss because the loss of the socket connection is still the same even though the cable loss has dropped to 1%.

 

There is a calculation for inductance losses but it is not relevant for one off jobs.

[BobL]

Assuming the connections, wiring, the outlet and breaker are OK.

 

100ft of 10 ga copper has a resistance of about 0.1 ohms (8 gauge is 0.06 ohms)

 

When carrying 15A this is Voltage drop of about 1.5V for the 100 ft long extension lead.

 

In other words the wire is not going to be a problem

 

Connections could easily double this but should still not be a problem.

[SoCal Dave]

Thanks guys for all the information.  I plan on a purchase of the 10 gauge extension cord after the holidays. 

[Steve Sells]

you forget to mention feed wires need to be >125% of the nominal load.  Remember as voltage drops in a long run, the amperage will raise to compensate. at 120 volts a 15 amp load is 1800 watts needing a min os 18.75 amp capacity.     With a reduction to 110 volts that 1800 watts is drawing 16.3 amps,  needing 20.3. and at 105 volts,  17.4 amps needing 21.75

 

That is why many welders are rated to use 15 amp plugs/lines, but work best with 20 amp circuits. If your cord is getting warm, that is a problem, the ratings are to prevent heat building up in the power lines.   That heat reduces the ampaccity of the lines, so as it gets hot, resistance raises, making it heat even more, and then you have a failure, including breakers tripping and/or a fire.

 

Just filling in the gaps

[SoCal Dave]

Test:  I have a 100 ft 12/3 extension cord.  I tried welding with that on a 20 amp breaker outlet in my shop and it worked fine.  I didn't have it at full power and wire speed, but I don't need full power.  I 'm welding a hinge on a barn door that broke off.  So, I saved myself $100 which is the cost of the Harbor Freight 100 ft, 10/3 cord.  Thanks everyone for your input and suggestions.   

[Hillbillysmith]

Ther are aluminum/copper extension cord charts available. Google it. 10ga over 100 feet should be suitable enough to run a 110v welder. The rest of the circuit wel be the issue.... Too much of a headache, just drill it out and bolt the hinge on. Cheaper than a 100 foot extension with no chance of a fire in the barn.

-Hillbilly

[Jack Evers]

My line loss calculator gives 2.3 % at 15 amps. Not a problem, but as others have said, the wire between the breaker box and the outlet you'te using could be a bigger problem.