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rider89
 
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Default branch electric box question

wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to prohibit
using double #10's to get the amperage?
Reason is I have plenty of (free) #10 on hand and tube capacity is slightly
better with #10's.

thanks
bill

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rider89
 
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I guess derating would apply (6x 10ga THHN +8ga grounding) , in which case a
50a breaker may suffice?


bill


"rider89" wrote in message
.. .
wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to
prohibit using double #10's to get the amperage?
Reason is I have plenty of (free) #10 on hand and tube capacity is
slightly better with #10's.

thanks
bill


  #3   Report Post  
Doug Miller
 
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In article , "rider89" wrote:
wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to prohibit
using double #10's to get the amperage?


Yes, there is. Section 310-4 explicitly *permits* parallelling conductors of
size 1/0 or *larger*, and thus by implication prohibits it for smaller
conductors.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.
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rider89
 
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bummer..

thanks doug

bill

"Doug Miller" wrote in message
.. .
In article , "rider89"
wrote:
wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to
prohibit
using double #10's to get the amperage?


Yes, there is. Section 310-4 explicitly *permits* parallelling conductors
of
size 1/0 or *larger*, and thus by implication prohibits it for smaller
conductors.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.


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HorneTD
 
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rider89 wrote:
wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to
prohibit using double #10's to get the amperage?
Reason is I have plenty of (free) #10 on hand and tube capacity is
slightly better with #10's.

thanks
bill


310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and
larger, comprising each phase, neutral, or grounded circuit conductor,
shall be permitted to be connected in parallel (electrically joined at
both ends to form a single conductor). copyright 2002 National Fire
Protection Association.
--
Tom Horne


Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.


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Sasha
 
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Just wonder why parallel wires are permitted for #10 and lower and
prohibited for smaller wire sizes?

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rider89
 
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i would imagine that the theory is that smaller wire sizes are too easy to
tinker with regarding the clamping hardware at breakers, etc.
If one of the parallel wires became disconnected, there could be a severe
overload on the remaining conductor.
Bill

"Sasha" wrote in message
ups.com...
Just wonder why parallel wires are permitted for #10 and lower and
prohibited for smaller wire sizes?


  #8   Report Post  
Chris Lewis
 
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According to HorneTD :
rider89 wrote:
wanting to feed a branch box with a 60a breaker (#6 copper) thru EMT.

This may be a stupid question, but is there anything in the NEC to
prohibit using double #10's to get the amperage?
Reason is I have plenty of (free) #10 on hand and tube capacity is
slightly better with #10's.


310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and
larger, comprising each phase, neutral, or grounded circuit conductor,
shall be permitted to be connected in parallel (electrically joined at
both ends to form a single conductor).


Does it not also say that _each_ conductor must be the same size, and
each capable of carrying the full breaker current?

[Our code does.]

Which basically means you can parallel conductors to reduce end-to-end
resistance (voltage drop), but NOT to increase circuit ampacity.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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