[RE-wrenches] Temperature Compensation calcs for wire

[RE Ellison]

Don’t we have to use the more restrictive one?

 

Bob Ellison

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of William
Miller
Sent: Wednesday, January 22, 2014 7:32 PM
To: RE-wrenches
Subject: [RE-wrenches] Temperature Compensation calcs for wire

 

Friends:

 

I try to be rigorous in application of NEC codes to everything I do,
including wire sizing.  I understand that even though I am using conductors
rated at 90°C, the breakers I use have terminals rated at 75°C so when
deriving the values for ampacity for a given gauge from the tables, I have
to use the 75°C column.

 

What is not clear, however, is which column I use when applying temperature
derating.  Table 315(B)(2)(b) has a column for 75 and a column for 90.  I am
using 90° wire.  The values for 90° are much more generous than the 75°
values and I would like to use them.  Which is correct?

 

As always, thanks to everyone on this list for all of the help and advice.

 

William

 

 

Gradient Cap

Lic 773985

millersolar.com <http://www.millersolar.com/> 

805-438-5600

 

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