Paralell conductors to feed a piece of equipment

[infinity]

Type AC has no 'wire' grounding conductor to worry about.

There is nothing in 250.122 about increasing the size of the armor.

That's where I was going with this. I consider the AC cable armor to be similar to EMT, RMC, IMC, etc. when using it as an EGC in parallel. Regular old MC cable would be a different, MC-AP would be the same as AC or the other metallic raceways that qualify as an EGC.

 

[iwire]

That's where I was going with this.

I figured.

I consider the AC cable armor to be similar to EMT, RMC, IMC, etc. when using it as an EGC in parallel. Regular old MC cable would be a dirfferent, MC-AP would be the same as AC or the other metallic raceways that qualify as an EGC.

I agree.

 

[DARUSA]

Type AC has no 'wire' grounding conductor to worry about.

There is nothing in 250.122 about increasing the size of the armor.

Iwire in this tread you have a different opinion!!!
http://forums.mikeholt.com/showthread.php/87290-MC-Cable-in-parallel/page2

More like My point.
The code does not prohibit this installation but i dont know how we can meet the grounding requirements.

 

[infinity]

The code does not prohibit this installation but i dont know how we can meet the grounding requirements.

Statement sounds like a contradiction to me.

 

[LarryFine]

Statement sounds like a contradiction to me.

In our business, dealing with the NEC? Perish the thought!

 

[DARUSA]

Statement sounds like a contradiction to me.

If you were an inspector,will you approve a 800 amp panel with 4 sets of AC cable 3/0- 4 wires in parallel? I thing the code didn't mention it because parallel rules refers to conductors in parallel not cables assemblies in parallel.

 

[infinity]

If you were an inspector,will you approve a 800 amp panel with 4 sets of AC cable 3/0- 4 wires in parallel? I thing the code didn't mention it because parallel rules refers to conductors in parallel not cables assemblies in parallel.

Yup, it may not be the best design, but unless someone can provide me with a code reference that says it's not permitted I see nothing wrong with what you've proposed.

 

[iwire]

Iwire in this tread you have a different opinion!!!
http://forums.mikeholt.com/showthread.php/87290-MC-Cable-in-parallel/page2

That thread you linked to is about MC cable not AC cable.

The code does not prohibit this installation but i dont know how we can meet the grounding requirements.

Of course we can.

 

[iwire]

If you were an inspector,will you approve a 800 amp panel with 4 sets of AC cable 3/0- 4 wires in parallel?

Yes, just like I would approve an 800 amp panel using four sets of 3/0s in 2" EMT using the EMT as the equipment grounding means.

I thing the code didn't mention it because parallel rules refers to conductors in parallel not cables assemblies in parallel.

The code clearly talks about both.

 

[DARUSA]

That thread you linked to is about MC cable not AC cable.




Of course we can.

Original post is for AC and MC.

 

[DARUSA]

Yes, just like I would approve an 800 amp panel using four sets of 3/0s in 2" EMT using the EMT as the equipment grounding means.





The code clearly talks about both.

The fault in a 200amp feeder is not the same as the 800 amp.
For this reason, table 250.122 require different size of ground wire!!!!
Now do we know if 3/0 AC cable (200 amp) is texted for the same amount of fault that can occur in a 800 amp feeder?

 

[infinity]

The fault in a 200amp feeder is not the same as the 800 amp.
For this reason, table 250.122 require different size of ground wire!!!!
Now do we know if 3/0 AC cable (200 amp) is texted for the same amount of fault that can occur in a 800 amp feeder?

Isn't it possible that the parallel jackets of the cable (their EGC's) would be sufficient to carry the fault current? Same as is permitted by 250.102(C)?

 

[iwire]

The fault in a 200amp feeder is not the same as the 800 amp.

I agree the 800 amp feeder will likely have a higher instantaneous trip setting than a 200 amp feeder.

For this reason, table 250.122 require different size of ground wire!!!!

Yes

Now do we know if 3/0 AC cable (200 amp) is tested for the same amount of fault that can occur in a 800 amp feeder?

I don't know that.

And I don't have to know that anymore than I would have to know that a 2" EMT can take an 800 amp fault in my example I gave above.

Why don't I need to know that?

Because 250.118 tells us that type AC cable can be used as an EGC.

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing
the circuit conductors shall be one or more or a combination
of the following:

(8) Armor of Type AC cable as provided in 320.108.

320.108 Equipment Grounding Conductor. Type AC
cable shall provide an adequate path for fault current as
required by 250.4(A)(5) or (B)(4) to act as an equipment
grounding conductor.

Now unless you can show me a code section that changes the above for AC cable when used in parallel I will consider the question settled.

 

[iwire]

Isn't it possible that the parallel jackets of the cable (their EGC's) would be sufficient to carry the fault current?

Or even a single jacket?

 

[petersonra]

One could even argue that if the jacket of the cable were an adequate EGC, that in a parallel cabling arrangement that if there were an EGC inside the cable that one might be in violation of the code for hooking it up, while leaving it in the jacket but not hooked up would be legal. What a bizarre situation.

OTOH, I don't recall if the code says every EGC involved has to meet the requirements. Maybe only one of them has to.