Extension cords

[babzog]

Please help me understand something about extension cords. Normal household wire is 14 or 12 ga, usually for 15 or 20 A circuits, respectively. I know there are heavier guage wires used in places too, not concerned about those.

I have an extension cord that is 12 ga, but it is labelled as being for 15A / 1875w. So, why can 12ga romex carry 20A but the extension cord, also 12ga, only carry 15A?

 

[Strouty]

How long is the cord, the longer it is the less it can take.

 

[raskal]

multi-strand wire (extension cord) vs solid wire

actually, I have no idea

 

[sberry]

It helps reduce pressure drop when its heavily loaded. Mostly concerned with continuous loading or heavy motor load starts. Often used on construction sites where runs across long buildings are common and heavy sawing is routine.

I got one or 2 but havnt used them for years.

 

[JimVonBaden]

How long is the cord, the longer it is the less it can take.

Exactly!

Jim

 

[JimVonBaden]

I have another question, since we are talking extension cords.

What is the best compromise cord (12/14ga 100') for both price and durability? I have a couple cheap ones and they are looking ragged and need to be replaced.

Jim

 

[nolimits76]

I have another question, since we are talking extension cords.

What is the best compromise cord (12/14ga 100') for both price and durability? I have a couple cheap ones and they are looking ragged and need to be replaced.

Jim

My thoughts are buy the best you can afford.

I have some "standard" cords and some heavy duty ones. Without fail, I always grab the thicker heavy duty ones because I don't have to worry with them.

Now if the neighbor needs to borrow something....

 

[sweetcretin]

There are multiple things in play.

Romex is solid-core wire, the extension cord is stranded.

The Romex is mechanically joined at both ends, the extension cord is friction joined.

The plugs (NEMA Connectors) on extension cords are rated independently of the wire as is the insulation. You must use the lowest rating of the three.

The worst case use rating for the extension cord is far more extreme than the worst case use of the Romex.

Will your extension cord be in factory perfect condition for the life of the cord? Once installed, Romex rarely experiences degradation from handling, crushing, impact, or other abuse.

If you want, go look up a 10 gauge extension cord, you'll find that it's rated for only 15A as well. This is because increased gauge in most extension cords is not to improve current carrying capacity, but to limit voltage drop over the length of the run. (Admittedly, fixing one improves the other, but the intent is to only prevent voltage drop.)


Higher amperage cords do exist, but they generally have alternate NEMA connectors and are generally purpose built.

 

[shooting4life]

I have another question, since we are talking extension cords.

What is the best compromise cord (12/14ga 100') for both price and durability? I have a couple cheap ones and they are looking ragged and need to be replaced.

Jim

I bought a 100 foot 12 ga cord from Costco for about 40$. I think it is a good value, I ended up cutting it into 3 cords (50, 25 and 25) since that was more handy for my 2 car garage and I got tired of winding up a 100 foot cord that I needed 25 feet of. I am probably going to add a retractable extension cord in the future for ease of use in my driveway.

 

[sberry]

I like a 14 cord for heavy work. Shop for a deal at one of the box stores, maybe a couple cords. Contrary to popular belief a 100 ft of 16 has its uses, its cheap and if the service is sturdy works a circ saw just fine to zing off a board or 2 here and there. Light leaf blowers even a vacuum for a bit isn't fatal.

You can run a low power electric heater on a 14, you can run a chop saw at 50 ft from modern electric service. Does not much of anything to improve it but cost and wear your back out as well as making it an inconvenience beyond a medium duty cord for home brew types 10% of the time and some nice 25 ready made 16's for the rest of the stuff in life.

 

[sberry]

I bought a 100 foot 12 ga cord from Costco for about 40$. I think it is a good value, I ended up cutting it into 3 cords (50, 25 and 25) since that was more handy for my 2 car garage and I got tired of winding up a 100 foot cord that I needed 25 feet of. I am probably going to add a retractable extension cord in the future for ease of use in my driveway.

That is the reality of practical experience.

 

[sberry]

I find myself looking for 50 ft 16. Our buildings are big and its mostly for light battery charger and on rare occasion 4 1/2 grinder and 90% of the time I use a circ saw its down a 16. I found some 10 ft at a Walgreen, orange 3 conductor for 2$ in the sale section and I only bought 2. They were snatched up in a hurry, I should have dropped a 20 at least over that.

 

[JakeKohl]

multi-strand wire (extension cord) vs solid wire

actually, I have no idea

That's actually correct. There are other factors too that deal with how long it is and how it sheds heat.

 

[Stuart in MN]

Solid wire won't work for an extension cord, of course, but as far as the ampacity goes for 60hz current it doesn't matter if a wire is stranded or solid.

 

[sberry]

It should be taught in a high school life class, use a cord up a size that come on the appliance is a general all around rule of thumb. But, you can "overload " some wires for some time. An AC225 welder has a 12 cord hooked to a 50A circuit, under some circumstances it is allowed to be hooked to a 12 wire but in the event one cant or doesn't want to go minimum,,,, which most people think is a poor idea in this case,,,, I never heard a reliable account where hooking a buzzer to a 10 cable was the root cause of a fire.

 

[rancherbill]

Please help me understand something about extension cords.

Gauge in this context is referring to the physical outside dimension of the wire!

Solid wire is SOLID, extension cord wire is MULTI-STRAND. If you look at the cross section there is more copper in the solid - the extension has 'air' in it.

More copper = more current!

 

[JimVonBaden]

Thanks guys. I have a short 14 and a medium 14, but need a long (100') 12/14 for my leaf blower, as well as some light construction work requiring a drill and circular saw. My old one has taken a beating over the years being dragged over rough concrete.

I use a cheap HF roller to wind it up, but usually need the whole cord off the roller.

I am going to get a 25' or 50' on a real for my ceiling in the garage. It will be very handy.

Jim

 

[sberry]

I could use another light unit like I got that I move from side door apron to bench corner in the winter. Its a great little thing, I could do without the 3 way. The cord jacket is really durable. I got one on my service truck, must be near 20 yrs old and havnt done a thing to it. This one is semi outside for 7 months of the year.

 

[nehog]

Please help me understand something about extension cords. Normal household wire is 12 or 14 ga, usually for 15 or 20 A circuits, respectively. I know there are heavier guage wires used in places too, not concerned about those.

I have an extension cord that is 12 ga, but it is labelled as being for 15A / 1875w. So, why can 12ga romex carry 20A but the extension cord, also 12ga, only carry 15A?

multi-strand wire (extension cord) vs solid wire

actually, I have no idea

Lot of nope in this thread.

Stranded vs. solid? Nope, no difference.

There is (only) one reason: the connectors (plug and receptacle) are rated at 15 amps. Put 20 amp plugs and receptacles on it and it will be rated at 20 amps (and not 15!)

Yes, I do have (commercial) cords rated at 20 amps. Yes, they are 12 AWG.

 

[WildwoodChuck]

The plug is rated at 15amps X 120volts = 1800watts you could get a cord with #8 wire and to be UL listed it probably wouldn’t be rated over 1800watts

As far as the house you have multiple 15amp plugs on a circuit so 600w + 600w + 600w = 1800w but none of them overload the 15amp plug.

 

[babzog]

The cord is 50' IIRC. Intending to use it to connect my genny (loud obnoxious beast) on the far side of the van to my trailer. It's a a cord I have so I wouldn't have to go buy another. Going to run one electric heater plus battery charger, lights and either a second heater, nuker, coffee maker, kettle, sandwich maker, power tool, etc.

 

[Charles (in GA)]

As noted by Sweetcretin and others, the limiting factor is the plug and receptacle ends of the cords. They are rated at 15 amp if standard parallel blade ends, doesn't matter what the gauge of wire is, the lowest common denominator is the plug and receptacle ends.

I just picked up a small 16 gauge cord I have, and it has a shiny tag wrapped around the cord at the plug that says 10 amp. In this case, the wire is the lowest common denominator.

I have lots of extension cords, way more than I need. Some of the light 16 gauge cords, my Dad had bought to run a leaf blower, it worked fine on them, even several of them, doing gutters and the drive.

I have......

1 flat 50 ft 16 gauge (hate it)
3 round 50 ft 16 gauge (orange)
2 round 50 ft 16 gauge (blue.. flexible at low temps)
1 50 ft 12 gauge (yellow. quality cord with lighted end)
1 80 ft 12 gauge (pink... thermoplastic jacket, stiff, but OK in warm weather)
1 100 ft 12 gauge (yellow... Thermoplastic jacket, durable, it lay in the grass for a year providing power to the shop from the house)
1 100 ft 12 gauge (orange... thermoplastic, rarely used)
1 40 ft 12 gauge (green... thermoplastic jacket, never out of the package)
3 homemade 14 gauge cords.......... made from used Carol Super VuTron SJOOW 14/3 I got out of the scrap bins at work. All were longer, black with dirt and had pinched broken places in them. I made one 50 ft, one about 30ish ft and one 40ish foot. Soaked them in Tide (with the ends out of the water) and wiped them with a scrub pad, they looked nearly new. I used good quality ends on them (Pass & Seymour on one, Daniel Woodhead on one and Leviton on the other)

As already noted, 16 gauge have their uses. I can run my 4 amp or 6 amp battery charger on something, way away from an outlet, or use a couple to run the blower to blow the mower off over by the fence (don't want a mess up by the building)

Charles

 

[madosta]

FYI, "respectively" basically means in the order you already listed, so 14 AWG is for 15 amps and 12 AWG is for 20 amps, relative to NM wire.

Woop woop.

 

[babzog]

FYI, "respectively" basically means in the order you already listed, so 14 AWG is for 15 amps and 12 AWG is for 20 amps, relative to NM wire.

Woop woop.

Thanks for the catch, I've corrected my post.

 

[2ManyProjects]

Gauge in this context is referring to the physical outside dimension of the wire!

Wrong. "Gauge" (specifically AWG) refers SOLELY to the cross-sectional area of the conductor(s), period.

Solid wire is SOLID, extension cord wire is MULTI-STRAND.

True, but irrelevant.

If you look at the cross section there is more copper in the solid

Wrong again. The conductors in a stranded AWG 12 (or whatever) wire have EXACTLY the same total cross-sectional area as a same-gauge solid wire. The stranded one will (usually) have a slightly larger overall diameter, due to the space lost to the inter-strand gaps; however, there are "formed" stranded wires which reduce those inter-strand gaps to essentially zero.

the extension has 'air' in it.

Again, true, but irrelevant.

More copper = more current!

The ONLY way to get "more copper" is to go to a larger (lower AWG number) wire.

Lot of nope in this thread.

Stranded vs. solid? Nope, no difference.

There is (only) one reason: the connectors (plug and receptacle) are rated at 15 amps. Put 20 amp plugs and receptacles on it and it will be rated at 20 amps (and not 15!)

BINGO!

The cord is 50' IIRC. Intending to use it to connect my genny (loud obnoxious beast) on the far side of the van to my trailer. It's a a cord I have so I wouldn't have to go buy another. Going to run one electric heater plus battery charger, lights and either a second heater, nuker, coffee maker, kettle, sandwich maker, power tool, etc.

While I appreciate the apparent economic incentive to make do with what you have, that sounds like an AWFUL lot of load to put on on an AWG 12 extension cord, especially one as long as that. The heater(s), the microwave, and the coffee maker are ALL large-ish loads, in and of themselves; the power tools may or may not be, depending. How large is the generator? Unless it is at least a 3KW model, it is rather questionable as to whether it could support more than one of them at a time. Figuring 25 Amps (3,000W / 120V) over 50 feet, I'd want AWG 10 to keep voltage drop under control. But OTOH, no "standard" extension cord you might have lying around will have the correct connectors (NEMA L5-30R/L5-30P) for that sort of current; so in effect, you'll probably be limited to 15-20 Amps, at most.

 

[JakeKohl]

Lot of nope in this thread.

Stranded vs. solid? Nope, no difference.

I had to research that and I stand corrected!

 

[babzog]

While I appreciate the apparent economic incentive to make do with what you have, that sounds like an AWFUL lot of load to put on on an AWG 12 extension cord, especially one as long as that. The heater(s), the microwave, and the coffee maker are ALL large-ish loads, in and of themselves; the power tools may or may not be, depending. How large is the generator? Unless it is at least a 3KW model, it is rather questionable as to whether it could support more than one of them at a time. Figuring 25 Amps (3,000W / 120V) over 50 feet, I'd want AWG 10 to keep voltage drop under control. But OTOH, no "standard" extension cord you might have lying around will have the correct connectors (NEMA L5-30R/L5-30P) for that sort of current; so in effect, you'll probably be limited to 15-20 Amps, at most.

Genny is currently a 6.5kw. Looking for a slighty smaller one for the trailer, 3-5kw, as this is my home emerg genny.

So, here's my puzzlement. If I have a long-ish run of 12/2 romex in the home to run a few things (say, basement workshop), what is the difference between that and an extension cord, also 12ga (leaving the issue of connectors aside for now)? Why would I have a voltage drop issue with the ext cord and not the romex?

I have limited the power use in the trailer to 20A by using a breaker as a "main". I have three 15A branch circuits within for plugs and lights. Using 12/2 for incoming power feed from external receptacle (marinco 15A "battery charger" receptacle) and 12/2 and 14/2 inside.

 

[2ManyProjects]

Genny is currently a 6.5kw. Looking for a slighty smaller one for the trailer, 3-5kw, as this is my home emerg genny.

The "Inverter"-type gensets popularized by Honda (but also nicely done by Yamaha and others) are THE way to go for any application where you're going to be within earshot. They're also MUCH more efficient in variable-load situations, as they don't have to run the engine at full speed to maintain 60 Hz output, even when there is very little load on the generator.

So, here's my puzzlement. If I have a long-ish run of 12/2 romex in the home to run a few things (say, basement workshop),

That must be a VERY sparsely equipped workshop. 12-2 NM-B ("Romex" is Southwire's tradename for that) is good for AT MOST 20 Amps; and if indeed it is a "longish run", you may be effectively limited to even less by voltage drop.

what is the difference between that and an extension cord, also 12ga (leaving the issue of connectors aside for now)?

Well, leaving aside semi-trivial issues like the extension cord being far more subject to damage (or even just degradation from normal wear & tear), the fundamental principles are the essentially same. You need to consider not only the raw ampacity of any given AWG wire, but also the potential for voltage drop over whatever length that wire is.

And not to put too fine a point on it, BUT... You really CAN'T "[leave] the issue of connectors aside". They are just as much a part of the circuit as anything else. And the whole circuit MUST be judged by its lowest-capacity component (chains vs. weak links, and all that).

Why would I have a voltage drop issue with the ext cord and not the romex?

As noted above, you very well MIGHT have a voltage-drop issue with the Romex.

I have limited the power use in the trailer to 20A by using a breaker as a "main". I have three 15A branch circuits within for plugs and lights. Using 12/2 for incoming power feed from external receptacle (marinco 15A "battery charger" receptacle) and 12/2 and 14/2 inside.

You were doing fine up until you mentioned that Marinco 15A power inlet. Go back to what I just said above about the circuit being limited by its lowest-capacity component. In this case, that's the power inlet connector. Hence, that breaker you installed to "[limit] the power use in the trailer" needs to be 15A, not 20A.

However, if it were MY trailer, I'd go the other way: Replace that power inlet with something like this:

http://www.marinco.com/product/30-amp-125-volt-contoured-power-inlet-stainless-steel-trim

or this:

http://www.marinco.com/product/30-amp-125-volt-power-inlet-stainless-steel

and make the interior wiring run from that inlet to your breaker panel at least AWG 10. Then use a PROPER 30A-rated shore-power cord to connect the genny.

At this point, you can also upgrade that "Main" breaker to 30 Amps, if you like. With as much "stuff" as you apparently want to run, this is NOT overkill.

 

[BellyUpFish]

Extension cords are great for burning down a house..