Ampacity derating - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Forum > General Electrical Discussion


Reply
 
Thread Tools Display Modes
Old 02-16-2015, 01:07 PM   #1
Senior Member
 
Join Date: Nov 2008
Location: tn
Posts: 586
Rewards Points: 588
Default Ampacity derating

Having a brain spasm, code not close by. We have 9 ccc in a pipe #10 and If I recall correctly we can derate from 40amp. This would put it at .70 X 40=28 amps. Can we still go with the 30 amp breaker because of the next size higher even though the adjustments puts us at 28 amps? Can't recall all the rules for this. Not sure how the inspector would see this install.

The other pipes got at least 12 ccc. So # 8 is being used because I am sure that it jumps to .50 reduction.
brother is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 02-16-2015, 01:30 PM   #2
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 21,444
Rewards Points: 1,830
Default

Yes #10 is good for 40 amps at 90C so with 70% you would be good at 28 amps. As long as the calculated load is not greater than 28 amps then you can use a 30 amp overcurrent protective device per 240.4(B)

12 current carrying conductor would require 50% reduction so 8 awg at 90C is 55 amps-- brings you to 27.5 at 50%. Next size applies again

Last edited by Dennis Alwon; 02-16-2015 at 01:32 PM.
Dennis Alwon is online now   Reply With Quote
Old 02-16-2015, 01:34 PM   #3
Member
 
Join Date: Jan 2015
Location: canada
Posts: 35
Rewards Points: 70
Default

In Canada we must use 75 degrees on everything except meter sockets
dave91 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 02-16-2015, 01:52 PM   #4
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 21,444
Rewards Points: 1,830
Default

Quote:
Originally Posted by dave91 View Post
In Canada we must use 75 degrees on everything except meter sockets
We must use 75C also but we can use 90C for derating. I believe you can also.

As long as the final overcurrent protective device is not greater than the weakest link- usually 75C you are okay.

If you use nm then you must use the 60 C rating in the NEC
Dennis Alwon is online now   Reply With Quote
The Following 2 Users Say Thank You to Dennis Alwon For This Useful Post:
51360 (02-16-2015), daveEM (02-16-2015)
Old 02-16-2015, 01:52 PM   #5
Senior Member
 
Join Date: Jan 2011
Location: canada
Posts: 1,483
Rewards Points: 2,080
Default

in canada for derating we can use 90C column but must not exceed 75
C column for final ampacity similar to nec
oliquir is online now   Reply With Quote
Old 02-16-2015, 02:23 PM   #6
Light Bender
 
eddy current's Avatar
 
Join Date: Feb 2009
Location: Canada
Posts: 5,398
Rewards Points: 7,830
Default

Quote:
Originally Posted by oliquir View Post
in canada for derating we can use 90C column but must not exceed 75
C column for final ampacity similar to nec
Can you quote the rule in the cec that says that?
eddy current is offline   Reply With Quote
The Following User Says Thank You to eddy current For This Useful Post:
51360 (02-16-2015)
Old 02-16-2015, 02:44 PM   #7
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 21,444
Rewards Points: 1,830
Default

Quote:
Originally Posted by oliquir View Post
in canada for derating we can use 90C column but must not exceed 75
C column for final ampacity similar to nec
That was my understanding but you will have to help with the code section.
Dennis Alwon is online now   Reply With Quote
Old 02-16-2015, 02:45 PM   #8
Member
 
Join Date: Jan 2015
Location: canada
Posts: 35
Rewards Points: 70
Default

If we take rule 4-006 (1) into consideration we would use 75 degrees and we would only use 90 degrees if we use subrule (2)
dave91 is offline   Reply With Quote
Old 02-16-2015, 03:14 PM   #9
Member
 
Join Date: Jan 2015
Location: canada
Posts: 35
Rewards Points: 70
Default

Google " BC module Derating " it says to derate using 90 degrees
dave91 is offline   Reply With Quote
The Following User Says Thank You to dave91 For This Useful Post:
sparky970 (02-17-2015)
Old 02-16-2015, 04:30 PM   #10
Senior Member
 
Join Date: Nov 2008
Location: tn
Posts: 586
Rewards Points: 588
Default

Thanks. co worker says apparently we cannot upsize because they are receptacles. is this true? Can't recall of the top of my head.
brother is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wire Ampacity Derating. Terminal temp rating vs Wire temp Rating Carultch NEC Code Forum 6 05-14-2013 12:36 AM
ampacity AFOREMA1 NEC Code Forum 2 05-10-2011 01:24 PM
Derating feeder ampacity in sunshine Shorty Circuit Commercial Electrical Forum 13 04-01-2011 09:32 PM
ampacity yetti NEC Code Forum 17 02-28-2011 03:43 AM
Ampacity Derating switchleg Residential Electrical Forum 35 11-23-2009 11:20 PM


All times are GMT -4. The time now is 03:56 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com