ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Elk’s Lodge 11th hour ritual chime clock
by lemahj - 09/26/23 10:24 AM
Strange breaker tip problem
by gfretwell - 09/25/23 08:13 PM
An impossible Support Violation
by gfretwell - 09/12/23 04:29 PM
How are you Jersey folks about the windmills?
by gfretwell - 09/08/23 02:21 PM
Having trouble logging in?
by Admin - 09/01/23 10:26 AM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 23 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Jun 2002
Posts: 186
M
mj Offline OP
Member
The average temp in my area in the summer is about 90- 105. as per sec, 310.16 table, if the temp exceeds 86 F ,a correction factor is required, as to derate the ampacity of the conductors. most of the electricians in my area do not apply the rules of 310.16 and 310.15(2)b tables. do you apply the rules of derating ?

Joined: Jun 2003
Posts: 1,143
D
Member
Wonder if your AHJ has allowed the non-derated temp to remain as the "accepted" one, since the temp is not year-round, and (hopefully) it gets cooler during the evening. I couldn't find anything specific for this during a (very) brief Code check.

You know the saying..."when in doubt, ask your AHJ"

Joined: Apr 2003
Posts: 362
Member
In my area I see seu/ser installed on commercial buildings. The conductors in the cable assembly are derated for residential. Inspectors seem to just let it slid?

Temp rating is only considered indoors?

Ob


Choose your customers, don't let them choose you.
Joined: Jan 2003
Posts: 4,391
I
Moderator
Obsaleet I do not follow your post.

SE is not restricted to dwelling units only.

As to the original question, I see the ambient temp derating issue as pretty much ignored.

If you ask an AHJ they should tell you that you must apply it.

In my area outside temps hit 100 F about once a year and temps in the 90s F are typical during August.

Say we have a 200 amp service that we choose 3/0 copper XHHW-2 (common for SE cable) for with a rating of 200 amps @ 75 C

Now if we have an ambient temp of 96 to 104 F that will be a .91 adjustment.

3/0 XHHW is rated 225 Amps @ 90 C

225 x .91 = 204.75 amps, still fine for the 200 amp service.

As a matter of fact any value above 175 amps and you could still protect the wire with a 200 amp breaker, as long as the derated ampacity was greater than the connected load.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Mar 2004
Posts: 32
S
Member
Keep in mind, in places with uncommon temperatures, that the equipment within the service itself is raited for certain temp. For instance, if lugs are not supplied with the switch gear, you must make sure they are rated the same temp as the switchgear... lugs come in several temperature ratings, and if they don't say, then they are asumed bye the AHJ to be the lowest rated. just something to add to the mix! Brian


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC + Exam Prep Study Guides Now Available!
 
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Scott35
Scott35
Anaheim, CA. USA
Posts: 2,722
Joined: October 2000
Top Posters(30 Days)
lemahj 1
Popular Topics(Views)
311,169 Are you busy
237,542 Re: Forum
221,306 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5