Rolling of coiling of Cable, NEC VIOLATION?

[yamaha_ridr]

I work overseas supporting the military. We have large 60 amp cables (SO)that are part of a pre packaged military tent city (Harvest Falcon). We were audited on the build by the military safety. They wrote up coiling of the cables. I can not find anywhere that it says that this can not be done. I know that we all have been told forever not to do this but can anyone tell me where this is a written rule or code violation and not just a recomendation. I have asked 3-4 other electricians and everyone has a different reason why you wouldn't do this, but no one can tell me where it is written.PLEASE I would like to put this to rest.:grin:

 

[e57]

I can think of no code violation.... However - it could slow down over current protection reaction time - as there would be some induced currents in the coil, changing circuit impedance - but that is a stretch.... (Since in a cable all of the conductors follow each other in the same path and negate each other, as well as being transposed - further negating the effect...)

 

[benaround]

With enough coils on a heavy loaded circuit you could exceed the temperature rating of

the cord, NEC violation.

 

[mxstar211]

The only thing I could think of is the bend radius of coiling the cables. Was it military or civillian that wrote you up? How much cable is coiled up? You may have problems with currents being induced. I was part of the initial start-up on TF-SAFE, and when we did our reports we had to site specfic NEC violations and we gave our NEC violation so they the problem could be corrected.

I am military, part of the 249th EN BN, if they can't give you a NEC reference, how can they tell you not to coil them.

 

[M. D.]

are'n t the conductors twisted inside the cable jacket ?,... why would coiling a set of twisted conductors matter

 

[realolman]

What SHOULD you do with them?

 

[M. D.]

I guess these would be out of the question,.. I would ask to see where it is prohibited

 

[cpal]

what is the frequency of the source? 60Hz or??

do you roll the cable after use and if how frequently?

are the energized cables left in a coil??

I saw a 400Hz power cart catch on fire because the feed cables were not rolled completely off the reel. As others have said, induced current.

If such regs are in writing the military is going to follow the op inst. regardless .

 

[iMuse97]

A coil of cable under significant load will create it's own additional heat as a coil, and it will retain the heat normally created by conduction, since it is insulating itself,
and I have seen one situation where it got hot enough to damage the insulation.
Granted this is not a likely possibility but probably the one that has the safety people concerned.

 

[iMuse97]

What SHOULD you do with them?

Stretch the cables out in a well-ventilated space with fans on them.:grin:

 

[ultramegabob]

are you talking about leaving a cable coiled while being used? I used to work for a guy that coiled his cables in a figure 8 fashion, he said it kept the cables from becoming a resistive load.

 

[don_resqcapt19]

I guess these would be out of the question,.. I would ask to see where it is prohibited

M.D.
The following is a quote of a typical instruction for using cord reels.

Fully extend cord before connecting any appliance to the cord reel.

Electrical reel ratings are based on a fully extended cord.​

 

[MarkyMarkNC]

I worked with a guy one time that was hot checking a house with a roll of 14-2 from the temp power to the service. The two were pretty close together so he just used a whole roll and unrolled a couple of feet off of each side to attach to the power pole and service.

After turning the breakers on, half the lights in the house were exceptionally bright, and the other half were really dim. Taking out his meter, he measured 160 volts on one leg, and 70 volts on the other. Figuring it was a POCO problem, he went back out to the temp panel, and that's when he noticed the coil of 14-2 had started to smoke and melt its insulation from the induced voltage on the magnetic field he had created.

This happened when this guy was really green and didn't know what the heck he was doing. It definitely wasn't me though.......just some guy I know. :roll:

 

[iMuse97]

I worked with a guy one time that was hot checking a house with a roll of 14-2 from the temp power to the service. The two were pretty close together so he just used a whole roll and unrolled a couple of feet off of each side to attach to the power pole and service.

After turning the breakers on, half the lights in the house were exceptionally bright, and the other half were really dim. Taking out his meter, he measured 160 volts on one leg, and 70 volts on the other. Figuring it was a POCO problem, he went back out to the temp panel, and that's when he noticed the coil of 14-2 had started to smoke and melt its insulation from the induced voltage on the magnetic field he had created.

This happened when this guy was really green and didn't know what the heck he was doing. It definitely wasn't me though.......just some guy I know. :roll:

Practical field-tested evidence! :grin: I always wanted to set up something like that in the apprenticeship school for the students to see. Not a bad idea (under a controlled situation). Of course, he was probably overloading the wire, too. OOooo!! Not good.

 

[RH1]

I worked with a guy one time that was hot checking a house with a roll of 14-2 from the temp power to the service. The two were pretty close together so he just used a whole roll and unrolled a couple of feet off of each side to attach to the power pole and service.

After turning the breakers on, half the lights in the house were exceptionally bright, and the other half were really dim. Taking out his meter, he measured 160 volts on one leg, and 70 volts on the other. Figuring it was a POCO problem, he went back out to the temp panel, and that's when he noticed the coil of 14-2 had started to smoke and melt its insulation from the induced voltage on the magnetic field he had created.

This happened when this guy was really green and didn't know what the heck he was doing. It definitely wasn't me though.......just some guy I know. :roll:

I don't understand how you connect an entire panel to 14-2 and get different voltages on each bus of the panel. I'm assuming both phases were connected to the hot and the neutral to the white. Were you feeding with 240 and the ground was your neutral?

 

[iwire]

that's when he noticed the coil of 14-2 had started to smoke and melt its insulation from the induced voltage on the magnetic field he had created.

I don't think it created any 'field' as you had two condutors canceling each other out.

I do think it could have been just a heat issue as you had so much bundled cable.

 

[skeshesh]

It's not a code violation but could be a violation of specs or utilization instructions. Also I'm sure the military has documents that set criteria for how work shall be performed.

As far as the coiled up cable heating issues, wow yet again I get great information from the forum's experienced members. I'm honestly considering taking some courses at a trade school or something like that since what is taught at most 4-year uni's is simply not enough for proper engineering, which is really sad they could easily have at least one course that deals with the realities in the field.

 

[kevinkk]

My understanding is when cable is coiled, especially large gauge service cord with more than one conductor under one jacket the cord will heat up due to magnetic field generated this effect is increased when the load per phase is out of balance. I cannot find a written ref. to this or a code section to site.

My field experience with temp power was to always figure 8 cable slack. A few benefits are that air space is created between the loops when they cross, it does not add twists to the cable when pull out of the figure 8 and it looks good.

 

[Johnmcca]

When I was in college, in the TV studio (1960's vintage equipment) we did the figure 8 coiling of the cable so it would pay out without kinking. If there was another reason we were never told.

 

[iwire]

My understanding is when cable is coiled, especially large gauge service cord with more than one conductor under one jacket the cord will heat up due to magnetic field generated this effect is increased when the load per phase is out of balance.

It is my understanding that even if 'out balance' all the current going one way matches all the current going the other way, there would be no magnetic field created.

With large gauge service cord comes large currents and often people choose to push the ampacity of these cords 'because they are temp' IMO this is where you get heating from.

My field experience with temp power was to always figure 8 cable slack. A few benefits are that air space is created between the loops when they cross, it does not add twists to the cable when pull out of the figure 8 and it looks good.

I agree.