12 guage extension cord wattage/amperage?

[The motor guy]

I have some prime 12 gauge 100 foot extension cords and they are rated at 15 amps 1875watts. My generator has 20 amp outlets on it. I've noticed that even their shorter 50 foot cords are still rated at 15 amps. I thought 20 amps was the most a 12 gauge cord could carry through a 50 foot cord? I'm curious as to if that's just a liability thing or what. Can I run 20 amps through 100 feet of extension cord is it's 12 gauge? What is the most a 12 gauge cord can actually run? Actually the load I'm trying to pull is 1900watts which ends up being 15.8amps. Would that small amount over 15amps be ok?

 

[BigCahuna]

It might get warm to the touch,but I take it you'll be using it outdoors, so I wouldn't worry about it. I've pulled at least that much thru 16 gauge cords at times with no problems.,,

 

[datech]

You are right the cord can handle as much current as you can feed through it... until it melts in two or starts a fire.

If you plan on running something for hours at a time be conservative, like 50% of the rated capacity. For a short period you can get away with an overload, but you might lose some efficiency due to voltage drop.

 

[The motor guy]

Are 12 gauge extension cords different from 12 gauge wire in a house? Or are they just being conservative and rating them at 15 amps instead of 20. If the cord is only just slightly warm to the touch then I assume it's ok. Right?

 

[datech]

Originally Posted By: motor_oil_madman
Are 12 gauge extension cords different from 12 gauge wire in a house? Or are they just being conservative and rating them at 15 amps instead of 20. If the cord is only just slightly warm to the touch then I assume it's ok. Right?


The wire itself should be the same except that

1) it's stranded wire with more surface area

2) the insulation would be different and might have more/less heat tolerance.

 

[Colt45ws]

Originally Posted By: datech
Originally Posted By: motor_oil_madman
Are 12 gauge extension cords different from 12 gauge wire in a house? Or are they just being conservative and rating them at 15 amps instead of 20. If the cord is only just slightly warm to the touch then I assume it's ok. Right?


The wire itself should be the same except that

1) it's stranded wire with more surface area

2) the insulation would be different and might have more/less heat tolerance.

Yes, the wire amperage rating changes depending on the insulation temperature rating. Due to the high flexibility required in this application, the insulation may have compromises in the temperature rating.
You'll probably be okay for 1900W. But, you will be dropping just over 5V across the cord. So, 120V at the Generator will be under 115V at the device. You'll end up closer to 16.5amps.
Its a generator; can you move it closer to the load?
Optimally, you would want a 10 gauge cord if this is not possible.

 

[jaj]

The original question is both simple and complex, and the answer goes like this:

- if the 1900 watt load is incandescent lighting (not fluorescent or HID) or it's a heater, then the 12 gauge will work fine PROVIDED that the cord is outdoors with good air circulation. 12 gauge is adequate for 20 amps, but the load will see reduced voltage, which means less heat or less light.

- if the 1900 watt load is a motor or ballasted lighting like fluorescent or HID, then use a 10 gauge cord. For these loads, as the voltage drops, current increases and that's bad for the motor or the ballast - it can burn them out. In short, use 10 gauge to reduce voltage drop, not because you need it to handle the current.

You didn't say what kind of connector is on the 12 gauge cords you have, but the rating of the assembled extension cord will be determined by the rating of the connector. If it's a regular flat-blade U-ground plug, then the plug is rated 15 amps. Twist-lok or 20 amp U-ground plugs (one blade turned sideways) will only be used on 20 amp rated cables, which can be made of 12 gauge wire or 10 gauge.

 

[The_Jeff]

Your only issue is voltage drop.

Building codes read that you have to have 12 ga for 20 amps or 14 ga for 15. But this provides various cushions for them heating up in insulation, etc. Their goal is less than 2-3% voltage drop, IIRC.

You'll notice a 10 ga wire coming from your car alternator that does 100 amps. It's shorter though, and there's (still) more voltage drop.

A 100 ft, 12 ga cord will have around the same drop as a 50 ft 14 ga one.

In short, what you're doing is okay. Temporary surges like a motor starting up won't overheat the cord.

I was an idiot once and ran my 2 hp air compressor off a 100 ft 16 ga cord. It started and ran fine but then started smelling hot and sounding unhappy. I shut it off, let it cool, and it's been fine ever since. Caught it just in time, I guess.

You'll know you have a good cord if it's insanely expensive. I got a 10 ga "Yellow jacket" for my welder and my wallet still hurts.

 

[Jarlaxle]

Originally Posted By: motor_oil_madman
I have some prime 12 gauge 100 foot extension cords and they are rated at 15 amps 1875watts. My generator has 20 amp outlets on it. I've noticed that even their shorter 50 foot cords are still rated at 15 amps. I thought 20 amps was the most a 12 gauge cord could carry through a 50 foot cord? I'm curious as to if that's just a liability thing or what. Can I run 20 amps through 100 feet of extension cord is it's 12 gauge? What is the most a 12 gauge cord can actually run? Actually the load I'm trying to pull is 1900watts which ends up being 15.8amps. Would that small amount over 15amps be ok?


DO NOT DO THIS! Unless the CORD is a 20-amp cord (if so, the plug's left blade will be horizontal), DO NOT EVEN THINK ABOUT DOING THIS!

 

[The motor guy]

Originally Posted By: eljefino
Your only issue is voltage drop.

Building codes read that you have to have 12 ga for 20 amps or 14 ga for 15. But this provides various cushions for them heating up in insulation, etc. Their goal is less than 2-3% voltage drop, IIRC.

You'll notice a 10 ga wire coming from your car alternator that does 100 amps. It's shorter though, and there's (still) more voltage drop.

A 100 ft, 12 ga cord will have around the same drop as a 50 ft 14 ga one.

In short, what you're doing is okay. Temporary surges like a motor starting up won't overheat the cord.

I was an idiot once and ran my 2 hp air compressor off a 100 ft 16 ga cord. It started and ran fine but then started smelling hot and sounding unhappy. I shut it off, let it cool, and it's been fine ever since. Caught it just in time, I guess.

You'll know you have a good cord if it's insanely expensive. I got a 10 ga "Yellow
jacket" for my welder and my wallet still hurts.

I paid like 90 dollars per cord. They're prime bulldog extension cords.

 

[The motor guy]

Originally Posted By: datech
Originally Posted By: motor_oil_madman
Are 12 gauge extension cords different from 12 gauge wire in a house? Or are they just being conservative and rating them at 15 amps instead of 20. If the cord is only just slightly warm to the touch then I assume it's ok. Right?


The wire itself should be the same except that

1) it's stranded wire with more surface area

2) the insulation would be different and might have more/less heat tolerance.


I've run close to 15 amps through this and can't feel any warmth at all through the cord so it handles current well.