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Survival and Preparations Long and short term survival and 'prepping'.

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  #1  
Old 07-14-2013, 1:58 PM
problemchild problemchild is offline
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Default Extension cords and generators (10-12-14ga?)

I know electricity travels down the surface of cables. Hence the reason welding cable is thousands of tiny braided strands (more surface area more amps). But why are extension cords all rated the same?

Example:

UL approved

25ft
14-12-10ga = 15 amps

50ft
14-12-10ga = 15 amps

100ft
12-10ga= 15 amps (except 14 which drops to 13 amps)

I was at Lowes and all the cables were rated the same 15 amps. What am I missing?
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  #2  
Old 07-14-2013, 2:15 PM
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If the plugs and sockets all have two parallel blades, that's a NEMA 5-15 Amp.

If one of the blades is perpendicular to the other it is a NEMA 5-20 Amp.

NEMA Connectors
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  #3  
Old 07-14-2013, 2:34 PM
problemchild problemchild is offline
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Quote:
Originally Posted by NickMc View Post
If the plugs and sockets all have two parallel blades, that's a NEMA 5-15 Amp.

If one of the blades is perpendicular to the other it is a NEMA 5-20 Amp.

NEMA Connectors
Ahhh limitation of the plug, OK, I get that. Then why have anything larger than 14ga wire if the plug cannot feed more amps to the 12 and the 10ga?

Why spend two to three times $$$ for the cord if it can only handle 15a?
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Old 07-14-2013, 2:53 PM
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Distance = resistance = heat
15 amps through 50 ft of 14 gauge stranded or solid.
Will get warm to hot. maybe hot enough to melt the insulation, causing the bare wires to touch, shorting out your generator.
Or
heat will reveal an imperfection in that extension cord, burning the wire open.

Same with 12 and 10 gauge.

Last edited by rick.benjamin; 07-14-2013 at 2:56 PM..
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  #5  
Old 07-14-2013, 3:20 PM
solarman solarman is offline
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Well to start...volts x amps = watts, right? If you have voltage drop than you are increasing amps. Your generator has a limit or ceiling on amps at the breaker, yes?

You want your generator running as efficiently as possible, right? Avoiding nuisance tripping and allowing your loads to run at proper voltage, especially electronic equipment.

You can use voltage drop calculators available on line to determine wire size or use a simple rule of thumb I use.
15amp load, #14 wire up to 50'.
20amp load, #12 wire up to 50'.
30amp load, #10 wire up to 50'.

Also you can test the cord under load. Take your wife's blow dryer and plug it in at the end of your cord, start your generator, turn the blow dryer on high. Pull the blow dryer plug out slightly and check your voltage with a decent meter. If over 3% get a bigger cord.

Hope this helps.
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  #6  
Old 07-14-2013, 3:26 PM
Bakersfield_Grizzly Bakersfield_Grizzly is offline
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Power loss is I^2 R So the reason for running a larger (10 or 12 ga) is you have less resistance therefore you have more usable power at the outlet. Unless you are running lights, I would try to stick to the 12 ga or 10 ga if you are really loading down your generator. By running too thin of wire you also have a tendency to burn up things.

I do not believe that the multistrand welding cords have as much to do with carrying amperage as being flexible. A single strand is not nearly as flexible as solid core and so you would never be able to wrap it up.

All the books I have ever read about electricity show that the amperage capacity has more to do with length. You can look up what your voltage loss is for a 100' run of 10, 12 and 14 ga.
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  #7  
Old 07-14-2013, 3:28 PM
Bakersfield_Grizzly Bakersfield_Grizzly is offline
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I bow to Solarmans response. Really good answer.
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  #8  
Old 07-14-2013, 3:54 PM
problemchild problemchild is offline
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Oh good to know, thanks.

I know DC has big limitations on distance running a 15,000lb winch front/rear on my diesel truck I had to run 2 huge cables to the back winch to supply the amps needed (600a) at only 15' away. I knew AC had some limitations but didnt know it was effected in such short runs like 25, 50 and 100.

So when I run the calc. it shows this for 12/100' at 15a

Based on what you say I have exceeded the 12ga length for 15a, correct? I would need 10ga for 100'?

Results:

Votage drop: 4.76
Votage drop percentage: 3.97%
Votage at the end: 115.24

http://www.calculator.net/voltage-dr...s=15&x=62&y=10




Quote:
Originally Posted by solarman View Post
Well to start...volts x amps = watts, right? If you have voltage drop than you are increasing amps. Your generator has a limit or ceiling on amps at the breaker, yes?

You want your generator running as efficiently as possible, right? Avoiding nuisance tripping and allowing your loads to run at proper voltage, especially electronic equipment.

You can use voltage drop calculators available on line to determine wire size or use a simple rule of thumb I use.
15amp load, #14 wire up to 50'.
20amp load, #12 wire up to 50'.
30amp load, #10 wire up to 50'.

Also you can test the cord under load. Take your wife's blow dryer and plug it in at the end of your cord, start your generator, turn the blow dryer on high. Pull the blow dryer plug out slightly and check your voltage with a decent meter. If over 3% get a bigger cord.

Hope this helps.

Last edited by problemchild; 07-14-2013 at 4:11 PM..
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  #9  
Old 07-14-2013, 4:31 PM
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Mathematicaly at 100' the voltage drop on the circuit isn't significant enough to warrant larger wire. But real world I say, and do say, when it comes to wire size and length, "it's better to be looking at it than for it."
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Old 07-14-2013, 5:13 PM
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Yes you are exceeding the rule of thumb, however you are so close in my mind it does not justify spending more money.

If however you were running a continuous load at a full 12 amps or more than #10 would be prudent.

Sounds like 100' is what you are shooting for? Bet you are running several small loads and maybe a refer. You want the generator about 100' away for noise, lets say.

I would run a nice fat #10 cord that I made myself with a WP plug into the gen-set and hard wired into a 4plex box, probably weather proof, and then some cheap #16-25' cords from there.

Or move the generator to 75' and use #12.
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Old 07-14-2013, 6:34 PM
problemchild problemchild is offline
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I just went and got a 50' 10ga and called it a day. Seems it will be good based on what you mentioned.

Thanks



Quote:
Originally Posted by solarman View Post
Yes you are exceeding the rule of thumb, however you are so close in my mind it does not justify spending more money.

If however you were running a continuous load at a full 12 amps or more than #10 would be prudent.

Sounds like 100' is what you are shooting for? Bet you are running several small loads and maybe a refer. You want the generator about 100' away for noise, lets say.

I would run a nice fat #10 cord that I made myself with a WP plug into the gen-set and hard wired into a 4plex box, probably weather proof, and then some cheap #16-25' cords from there.

Or move the generator to 75' and use #12.
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  #12  
Old 07-14-2013, 9:40 PM
solarman solarman is offline
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Good choice.
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  #13  
Old 07-15-2013, 8:23 AM
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Quote:
Originally Posted by problemchild View Post
I know electricity travels down the surface of cables. Hence the reason welding cable is thousands of tiny braided strands (more surface area more amps).

Just for the sake of accuracy, what you are talking about here is called the "skin effect" and it only affects AC circuits. Not DC.
Skin effect is proportional to the square root of the frequency. The higher the frequency the more the electrons want to travel along the outer surface or "skin" of a conductor, effectively reducing the conductors available cross sectional area.

At 60 Hz the skin depth is about 9 mm. So for any conductor smaller in diameter than 18 mm (3/4") the skin effect is a non issue.

Welding cables are made of many fine wires because it makes them more flexible. It has nothing to do with skin effect.

In fact having many fine wires does nothing to help the skin effect because the wires are all in contact with each other so they still act like one big conductor and at high frequencies the electrons will still want to travel through the outermost conductors in the bundle.
In order to combat skin effect by using many fine conductors you need to insulate each wire from the ones next to it. This is called Litz wire and it's quite expensive.

Anyway, that's a short primer on skin effect and for DC circuits it is non-existent and for most 60 Hz AC applications it is can be considered non-existent or negligible except in very large diameter conductors.


As far as extension cord size.. as has already been mentioned much of the reason for larger diameter wire is to minimize voltage drop across a long cord.

For a 100' cord carrying 15 amps the voltage lost =

14AWG = 7.58V (6.32%) 120V in = 112.42V out
12AWG = 4.76V (3.97%) 120V in = 115.24V out
10AWG = 3.00V (2.5%) 120V in = 117.0V out

Decide what you can live with and pay your money.


.
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  #14  
Old 07-15-2013, 8:46 AM
problemchild problemchild is offline
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Just amazing what you can learn off the internet by asking a question. So what happens with DC? Is it better to have many small or one large or does it not matter? I know to run the 15,000 winch to the back of my diesel truck it took two very big and heavy wires for the positive side only. We grounded the other side. My electronics buddy (now passed away- God bless him) figured out how much and how big I needed to put 600amps 12-15ft away with DC at 15v. He said once I started using them they would warm up and I would lose power.
Also a winch only cranks 15k on the last spool so you had to unwind all your cable and use pulleys to get a "full pull".

Thanks




Quote:
Originally Posted by Dubious_Beans View Post
Just for the sake of accuracy, what you are talking about here is called the "skin effect" and it only affects AC circuits. Not DC.
Skin effect is proportional to the square root of the frequency. The higher the frequency the more the electrons want to travel along the outer surface or "skin" of a conductor, effectively reducing the conductors available cross sectional area.

At 60 Hz the skin depth is about 9 mm. So for any conductor smaller in diameter than 18 mm (3/4") the skin effect is a non issue.

Welding cables are made of many fine wires because it makes them more flexible. It has nothing to do with skin effect.

In fact having many fine wires does nothing to help the skin effect because the wires are all in contact with each other so they still act like one big conductor and at high frequencies the electrons will still want to travel through the outermost conductors in the bundle.
In order to combat skin effect by using many fine conductors you need to insulate each wire from the ones next to it. This is called Litz wire and it's quite expensive.

Anyway, that's a short primer on skin effect and for DC circuits it is non-existent and for most 60 Hz AC applications it is can be considered non-existent or negligible except in very large diameter conductors.


As far as extension cord size.. as has already been mentioned much of the reason for larger diameter wire is to minimize voltage drop across a long cord.

For a 100' cord carrying 15 amps the voltage lost =

14AWG = 7.58V (6.32%) 120V in = 112.42V out
12AWG = 4.76V (3.97%) 120V in = 115.24V out
10AWG = 3.00V (2.5%) 120V in = 117.0V out

Decide what you can live with and pay your money.


.

Last edited by problemchild; 07-15-2013 at 9:10 AM..
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  #15  
Old 07-15-2013, 9:05 AM
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Quote:
Originally Posted by problemchild View Post
Just amazing what you can learn off the internet by asking a question. So what happens with DC? Is it better to have many small or one large or does it not matter?

Thanks
For DC it really doesn't matter. Things like flexibility & vibration resistance are usually the big considerations for choosing solid vs stranded (and how many strands) for most DC wiring.
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Old 07-15-2013, 9:28 AM
Californio Californio is offline
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Ancor Marine Wire, is all tinned and they use fine strands.

http://www.marinco.com/brand/ancor

They have some good info in the Tech section.

http://www.marinco.com/page/wire-tech-data
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