The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm▓ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Texas_Ranger 8
Trumpy 8
sparkyinak 7
Who's Online
1 registered (sparkyinak), 220 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#77646 - 07/06/01 12:08 AM Use of 90 degree rated cable
tmon Offline
Member

Registered: 07/05/01
Posts: 29
In Mike Holts "Masters Electrician Prep Book", he refers to the 90 degree column in T310-16 and states that this column is used primarily for ampacity derating. Has anyone else read or heard this?

Top
2014 / 2011 NEC & Related Books and Study Guides
#77647 - 07/06/01 03:32 AM Re: Use of 90 degree rated cable
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Hi tmon,
yes , we are allowed to use the highest figure to start derating calc's from, i believe there was a code cycle to clear this up, but am at a loss this morning for an article...

Top
#77648 - 07/06/01 03:34 AM Re: Use of 90 degree rated cable
Glenn Offline
Member

Registered: 01/17/01
Posts: 78
It's always been that way.

Most earier Circuit Breakers ( small size ) were rated for 60┬║ terminations.

Now many are rated for 60/75┬║ terminations.

Usually only high voltage systems and bus work is the only items rated for 90┬║ terminations.

Look at the labeling within panels and on equipment terminal info.

Also NEC 110-14(c) must be followed. Although is has only been in the NEC the last few cycles, it has always been in 110-3(b) and the UL White book has had the info for many mnay years, usually with-in the first 8 pages of text.

Glenn

Top
#77649 - 07/07/01 04:50 AM Re: Use of 90 degree rated cable
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
thanks Glenn

Top
#77650 - 07/07/01 11:54 AM Re: Use of 90 degree rated cable
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
tmon,

Welcome to the group!!!

Just wanted to point out one of the more "simpler" points on using the 90 degree column for derating is the reason we can put upto 9 current carrying conductors [#12 THHN cu] in the same raceway, and still have them rated at 20 amp max.
What is being done here is the 30 amps maximum for #12 in the 90 degree column is used for the derating number - so for 9 current carrying conductors, 70% of 30 amps is 21 amps.

Scott SET.

 Quote:
Originally posted by tmon:
In Mike Holts "Masters Electrician Prep Book", he refers to the 90 degree column in T310-16 and states that this column is used primarily for ampacity derating. Has anyone else read or heard this?
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals