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Old 05-10-2016, 10:45 PM   #21
ODH
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Quote:
"WARNING
The power cord must be fully extended when in use and not left coiled in the
electrical compartment or on the ground. If the power cord is left coiled, it may potentially create enough heat to melt its protective casing."
A lawyer wrote that not an engineer.
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Old 05-11-2016, 10:14 AM   #22
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A lawyer wrote that not an engineer.
x2
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Old 05-11-2016, 10:59 AM   #23
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A lawyer wrote that not an engineer.
An engineer won't sue your company because he did something that was not absolutely, perfectly and well-thought-out safe.
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Old 05-11-2016, 11:47 AM   #24
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As an employee of an electrical engineering firm,
I pull my cord all the way out, and do not coil it.
It's never been hard to get it back in the storage area.
If I could find proof of the cable being rated @90°c, I might think otherwise.
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Old 05-11-2016, 12:02 PM   #25
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As an employee of an electrical engineering firm,
I pull my cord all the way out, and do not coil it.
It's never been hard to get it back in the storage area.
If I could find proof of the cable being rated @90°c, I might think otherwise.
As an employee of an electrical engineering firm you should know that all cables are required to be imprinted with their wire size and type. Look at your cable and see what size and type then look it up in the NEC.

Mine is marked as #10AWG, Type STW, rated at 105C.
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Old 05-11-2016, 12:07 PM   #26
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As an employee of an electrical engineering firm you should know that all cables are required to be imprinted with their wire size and type. Look at your cable and see what size and type then look it up in the NEC.

Mine is marked as #10AWG, Type STW, rated at 105C.
Touché.

Based on that rating, (if they think it's going to get that warm),
All the more reason to get it all out of the cabin.
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Old 05-11-2016, 01:20 PM   #27
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Touché.

Based on that rating, (if they think it's going to get that warm),
All the more reason to get it all out of the cabin.
They don't think it's going to get that warm. That's just the max rating for the insulation used on type STW wire. Most all flex cord used for RV power cords is some type of Sxxx type wire. The specific type specifies the temperature where the insulation will begin to break down. Not the temperature that the wire will reach under normal use. Also note the temp rating is in Celsius and not Fahrenheit. 105C is around 220F. Slightly higher than the boiling point of water. Your shore cord will never see those temps unless something is very wrong. Certainly it won't get that hot form being coiled.
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Old 05-11-2016, 02:43 PM   #28
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I don’t pull mine out all the way either most of the time but you are better off to do so unless using reduced load. RV cords are good quality and relatively large but the warnings are still there for a reason.

Coiling reduces the ability to dissipate heat and as heat increases so does resistance further adding to increased heat which is why in some cases the insulation can be compromised. The electrical code deals with safe heat dissipation by reducing the allowable ampacity for cords when in close proximity for a distance of 600mm (23”) or more which occurs when coiled. The #10 STW cord with 2 current carrying conductors is rated for 30A max load. Electrical Code rules for cords reduce the max current to allow for safe heat dissipation as follows: 2-3 coils = 80% or 24A max load; 4-12 coils = 70% or 21A max load; 13-21 coils = 60% or 18A max load; 22+ coils = 50% or 15A max load.

So you can see that there are actual reasons not to coil an extension cord and especially longer ones with smaller cable size carrying close to their max load. The percentages for reducing max current apply to all rated cord ampacities.

The myth part is around induction. In a 2 wire AC cct no induction occurs because the voltage and current curves in the two conductors are exactly opposite at any given time and effectively cancels to zero. Induction, eddy currents, sheath currents etc. are a problem with single conductor AC cables and there are different precautions and install methods to correct for it.
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Old 05-11-2016, 02:57 PM   #29
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What I would like to know is when you pull all 25' feet of cable out of the storage compartment, what do you do with the extra 10-15'? Leave it in a nice coil on the ground I'll bet. Any time I've looked in my storage compartment, the wire is anything BUT neatly coiled.
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Old 05-11-2016, 03:22 PM   #30
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I don’t pull mine out all the way either most of the time but you are better off to do so unless using reduced load. RV cords are good quality and relatively large but the warnings are still there for a reason.

Coiling reduces the ability to dissipate heat and as heat increases so does resistance further adding to increased heat which is why in some cases the insulation can be compromised. The electrical code deals with safe heat dissipation by reducing the allowable ampacity for cords when in close proximity for a distance of 600mm (23”) or more which occurs when coiled. The #10 STW cord with 2 current carrying conductors is rated for 30A max load. Electrical Code rules for cords reduce the max current to allow for safe heat dissipation as follows: 2-3 coils = 80% or 24A max load; 4-12 coils = 70% or 21A max load; 13-21 coils = 60% or 18A max load; 22+ coils = 50% or 15A max load.

So you can see that there are actual reasons not to coil an extension cord and especially longer ones with smaller cable size carrying close to their max load. The percentages for reducing max current apply to all rated cord ampacities.

The myth part is around induction. In a 2 wire AC cct no induction occurs because the voltage and current curves in the two conductors are exactly opposite at any given time and effectively cancels to zero. Induction, eddy currents, sheath currents etc. are a problem with single conductor AC cables and there are different precautions and install methods to correct for it.
What NEC article are you referencing? And neutral is not a "current carrying conductor" according to the NEC. It is the "grounded conductor" and the green wire is the "grounding conductor". There is only a single "current carrying conductor" in a 30A shore cord.

A lot of times folks look something up on Google regarding the NEC. However, they don't pay attention to the definitions of conductor types or what the that particular article is discussing. I've seen folks quote NEC articles regarding the wiring of hospital generator feeds like they apply to RVs. Or current derating for multiple conductors of a 3-phase system in metallic conduit like it applies to a RV shore cord. Just wondering what article of the NEC requires derating of coiled shore cords. I'm fairly familiar with the NEC but I might have missed something.

You'd think the folks who manufacture cord reels and get them tested by UL would understand the coiled cord derating requirement of the NEC.


And I think I'm done with flogging this deceased equine. If folks want to worry about a coiled shore cord setting their rig on fire that's fine with me. But it won't.
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