# Insulating Bushing 300.4(F)



## swimmer (Mar 19, 2011)

I thought that there was a conduit size, above wich insulating bushings are required but when I read 300.4(F), it looks like this bushing is required for 4AWG non-grounded conductor regardless of conduit size.

So if I have a quantity of 60 #12 THHN wires in a 2" rigid conduit, an insulating bushing is not required.

Am I understanding this correctly?

Thanks


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## BBQ (Nov 16, 2010)

swimmer said:


> I thought that there was a conduit size, above wich insulating bushings are required but when I read 300.4(F), it looks like this bushing is required for 4AWG non-grounded conductor regardless of conduit size.
> 
> So if I have a quantity of 60 #12 THHN wires in a 2" rigid conduit, an insulating bushing is not required.
> 
> ...


You have it right, not required. 

But they are cheap and will not hurt.

Edit, rigid needs bushings, listen to Awd dawg


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## Awg-Dawg (Jan 23, 2007)

swimmer said:


> i thought that there was a conduit size, above wich insulating bushings are required but when i read 300.4(f), it looks like this bushing is required for 4awg non-grounded conductor regardless of conduit size.
> 
> So if i have a quantity of 60 #12 thhn wires in a 2" rigid conduit, an insulating bushing is not required.
> 
> ...


 

344.46


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## bruce6670 (Apr 27, 2010)

In the 2011 NEC it's 300.4 G. 

The purpose of the bushing is to protect the insulation of the heavier conductors. I guess the # 12 conductors don't have enough weight to really hurt the insulation. If it was me, I'd put the bushing on anyway. Even if it's just overkill.


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## bruce6670 (Apr 27, 2010)

Awg-Dawg said:


> 344.46



I wonder why there's a difference between conduit types. Is rigid more likely to damage conductors ?


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## Awg-Dawg (Jan 23, 2007)

bruce6670 said:


> I wonder why there's a difference between conduit types. Is rigid more likely to damage conductors ?


 
Your guess is what I would think.


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## Bkessler (Feb 14, 2007)

bruce6670 said:


> I wonder why there's a difference between conduit types. Is rigid more likely to damage conductors ?


I've cut myself on fresh rigid threads, and I've seen carelessness with a reamer where the end of the GRC gets pretty sharp too.


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## bruce6670 (Apr 27, 2010)

Bkessler said:


> I've cut myself on fresh rigid threads, and I've seen carelessness with a reamer where the end of the GRC gets pretty sharp too.


Good point.


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## wildleg (Apr 12, 2009)

Bkessler said:


> I've cut myself on fresh rigid threads, and I've seen carelessness with a reamer where the end of the GRC gets pretty sharp too.


if there's a connector on it, how does the wire ever rub against that sharp edge ?


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## jmsmith (Sep 10, 2011)

wildleg said:


> if there's a connector on it, how does the wire ever rub against that sharp edge ?


I have seen cases where rigid has been "over-reamed". This made the wall so thin on the end that the last thread will actually split and try to curl back into the coupling. This will slit wire insulation better than a utility knife in some cases. It is also hard to find in long runs-believe me!


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## chicken steve (Mar 22, 2011)

thou shalt bushing.....

~CS~


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