Heavy duty extension cords

[Dave Zellers]

Why are all the extension cords, even the 10/3 heavy duty extension cords, rated at 15 amps and 1875 watts?

Surely they can handle more but the only cords I can find that are rated 20 amps have 220 male plug. All the regular plug (120v) cords are rated 15 amps regardless of gauge. Seems odd.

[Tom M King]

Probably because the Edison style ends can fit in 15 amp receptacles, and I can't think of anything with a 15 amp Edison plug on the end of it that is over 15 amps. I have no idea about the code rules on it. 20 amp 120V has a different plug and receptacle configuration, as does 30 amp.

[Warren Lake]

these have worked fine, make your own.

491735491734

[glenn bradley]

Tom has it. The typical consumer grade U-ground receptacle is a 15amp device. If the cord has a typical NEMA 5-15 configuration it will be rated at 125v / 15 amps.

491736

I run 20 amp outlets that accept 15 and 20 amp physical plug form factors as shown in the lower right of the pic above. I have picked up 12ga SJO-like cord (or extension cords) on clearance here and there and have all the relatively high amperage cords I could use. When in doubt, spec and make you own.

[Andrew More]

Surely they can handle more but the only cords I can find that are rated 20 amps have 220 male plug. All the regular plug (120v) cords are rated 15 amps regardless of gauge. Seems odd.

I'm wondering what you have that:
1) Uses 20 amps
2) Is going to be plugged in
3) Isn't a welder which should probably be on 220V anyway.

I think there aren't any cords because there isn't enough demand.

[Warren Lake]

I have a milwaukee metal cutting saw that kept blowing out breakers on 15 amps. Car builder friend said put it on a 30 amp circuit. I took it back to be checked and they said it was fine.

Put it on a 20 amp circuit and no more blown breakers. I guess the start up transient was too much for the breaker, I did put a new breaker in when on 15 amp as I know they weaken after snapping off some number of times and it still took the new one out. 20 amp no more issues. Dont like cutting metal that way either, its a spark throwing machine but metal at the time too wide for the metal cutting bandsaw.

[Dave Zellers]

I'm wondering what you have that:
1) Uses 20 amps
2) Is going to be plugged in
3) Isn't a welder which should probably be on 220V anyway.

I think there aren't any cords because there isn't enough demand.

First- thanks to all for the replies- I'm starting to understand why it's this way.

To Andrew's point: This is about providing power from my Generator (Honda EG2800IA) to power 2 refrigerators, microwave, toaster oven, 2 burner hot plate, coffee maker and random lights. NOT all at the same time. I have a 25 foot 30 amp 125 volt 3750 watt extension cord Nema L5-30P to three 5-15R coming into the house. Actually the basement fridge comes off a separate 20 amp plug on the generator. I have already run this system minus the hot plate successfully using 12 gauge cords off this 30 amp cord. I have just bought these: https://www.amazon.com/dp/B08NFGTS8J and want to plug them both into this 30 amp cord to run the fridge and microwave on one and the future hot plate and toaster oven off the other. Again, not all at once. But the watts on each individually will exceed 1875 (I think) if the fridge and microwave are running at the same time OR if the hot plate and toaster oven are running at the same time. How can a 10 gauge cord not handle that?

That's my confusion.

[Paul F Franklin]

They are available. Search for Nema 5-20 extension cord. They have the correct ends to plug into a 20 amp receptacle and take a 20 amp plug. Of course they are more expensive than normal cords.

[Bill George]

Already been covered but all the outlets I purchase are 20 amp rated and I pay extra for that. I too run a generator that feeds 20 rated cords to feed some circuits in the house. I do not cheap out on outlets or cords.

[Myk Rian]

If the generator has 240 out, you are much better off using it.
Otherwise you would need 2 extension cords to feed the 2 120v legs.

[Dave Zellers]

No 240v. But a 30 amp 120v plus two separate 20 amp 120v's.

Outside of my generator situation, we recently built a sun room and I specified 2 separate 20 amp circuits, using 12 gauge solid wire, wanting to keep a potential air conditioner separate from the other plugs. All the receptacles are regular looking 120 volt receptacles. It just seems silly to me that if I were to plug in my 10 gauge stranded wire heavy duty cord, it is rated at 15 amps and 1875 watts off that outlet.

Back to the generator, my question is about exceeding the 1875 watt rating of the cord. I don't see how that is possible with a 25 foot 10 gauge cord feeding into a 25 foot 3750 watt 30 amp cord.

[Paul F Franklin]

No 240v. But a 30 amp 120v plus two separate 20 amp 120v's.

Outside of my generator situation, we recently built a sun room and I specified 2 separate 20 amp circuits, using 12 gauge solid wire, wanting to keep a potential air conditioner separate from the other plugs. All the receptacles are regular looking 120 volt receptacles. It just seems silly to me that if I were to plug in my 10 gauge stranded wire heavy duty cord, it is rated at 15 amps and 1875 watts off that outlet.

Back to the generator, my question is about exceeding the 1875 watt rating of the cord. I don't see how that is possible with a 25 foot 10 gauge cord feeding into a 25 foot 3750 watt 30 amp cord.

If you wanted nema 5-20 receptacles on your 20 amp circuit you would have had to specify them. While 20 amp circuits in residents are common (and required for rooms like the kitchen), they are generally equipped with nema 5-15 receptacles rated for 15 amps. So the total load on the circuit can be 20 amps, but only 15 amp max on a single receptacle. Very few home appliances are designed to draw more than 15 amps. But it would not be unusual to have two appliances plugged into the same kitchen circuit that together draw more than 15 amps, hence the rationale for the 20 amp circuit with 15 amp receptacles.

You're not going to overload the wire in your cord, but you may overload the plug and receptacle, since they are only rated for 15 amps. They are the limiting factor, not the wire gauge (in your example). An occasional overload won't damage them instantly, but long term use might cause them to overheat. The reason they make cords with 10 or 12 gauge wire and 15 amp ends is to limit the voltage drop in the cord. Not usually important for short cords, but definitely an issue on longer cords used with heavy draw tools or such.

[Dave Zellers]

If you wanted nema 5-20 receptacles on your 20 amp circuit you would have had to specify them. While 20 amp circuits in residents are common (and required for rooms like the kitchen), they are generally equipped with nema 5-15 receptacles rated for 15 amps. So the total load on the circuit can be 20 amps, but only 15 amp max on a single receptacle. Very few home appliances are designed to draw more than 15 amps. But it would not be unusual to have two appliances plugged into the same kitchen circuit that together draw more than 15 amps, hence the rationale for the 20 amp circuit with 15 amp receptacles.

Yes- I know I confused the issue with my sun room example. Apologies for that. And thanks- every reply thus far has been another piece in the puzzle for me.


You're not going to overload the wire in your cord, but you may overload the plug and receptacle, since they are only rated for 15 amps. They are the limiting factor, not the wire gauge (in your example). An occasional overload won't damage them instantly, but long term use might cause them to overheat. The reason they make cords with 10 or 12 gauge wire and 15 amp ends is to limit the voltage drop in the cord. Not usually important for short cords, but definitely an issue on longer cords used with heavy draw tools or such.

Yes that was my sun room example diversion but in this case I'm plugging into a 30 amp 3750 watt 10/3 cord coming off my generator.

I'm being obtuse I know. But seriously, how can a 10 gauge cord max out at 1875 watts? I guess these are rated very conservatively.

Could it be that the two ends are built more robustly on the 30 amp cord?

[Bruce Wrenn]

No 240v. But a 30 amp 120v plus two separate 20 amp 120v's.

Outside of my generator situation, we recently built a sun room and I specified 2 separate 20 amp circuits, using 12 gauge solid wire, wanting to keep a potential air conditioner separate from the other plugs. All the receptacles are regular looking 120 volt receptacles. It just seems silly to me that if I were to plug in my 10 gauge stranded wire heavy duty cord, it is rated at 15 amps and 1875 watts off that outlet.

Back to the generator, my question is about exceeding the 1875 watt rating of the cord. I don't see how that is possible with a 25 foot 10 gauge cord feeding into a 25 foot 3750 watt 30 amp cord.Other than camp ground outlets for motor homes, I know of no other 30 amp, 125 volt plugs. The plug determines amperage rating. The receptical on your generator, is it a twist lock? If so is it a three prong, or four prong outlet?

[Mike Cutler]

Dave
They do make them. I have two of them.
The two I have are 100’ long and have molded 120/ 20 amp plugs and receptacle on both ends. They were also pretty expensive. They solved a very specific need at the time, and have been stored since then.
If a manufacturer puts a 15 amp mounded plug on the extension cord, that is it’s UL rating.
The jacket insulation material, and individual conductor insulation material, as well as total length, will also be factored into the total overall rating. It’s not just as simple as AWG.
As to plugging one extension cord into another?
It is done millions of times daily, but you will be very hard pressed to find any manufacturer of extension cords, with UL certification, that condones the practice, or has tested for it.
For generators, don’t “gang” extension cords. Buy the correct “SO Cord” and make them, or have them made.
You would be better served with your current generator options by making a single 240/30Amp cord to a 120vac breakout box. You can also buy these online.
The NEC stops at the duplex receptacle on the wall. After that it’s up to you. Be conservative and safe.

[Tom M King]

I'm still using some cords I made up from 12/3 SO and Hubbell ends in the late '70's. I've had to replace a few ends because the connections inside had loosened and arced, but only a couple.

[Dave Zellers]

Other than camp ground outlets for motor homes, I know of no other 30 amp, 125 volt plugs. The plug determines amperage rating. The receptical on your generator, is it a twist lock? If so is it a three prong, or four prong outlet?

Yes it is a twist lock and the cord is a Nema L5-30P to three 5-15R. The generator also has two separate 20 amp receptacles.

[Dave Zellers]

If a manufacturer puts a 15 amp mounded plug on the extension cord, that is it’s UL rating.

Yeah, that makes sense.

Much thanks to all. Very helpful.

[Jim Becker]

My solution is just to re-terminate the cord with the plugs/receptacles that are appropriate for the useage. For example, I have a few 240v extensions I made from 120v extension cords that have the appropriate gage for my application(s) It's a little harder to find 10 gage that don't cost a fortune, however, but 12 gage that will support 20 amps are easy to buy inexpensively. As Mike mentioned, you can buy SOxx type cable by the foot (10 gage is about $3 a foot right now...I bought some for my new slider the other day to make up a cord) to handle the 30 amp stuff.

Do note that length matters...