#12 AWG on 25 amp OPD - 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 05-12-2010, 09:17 PM   #1
Les Voltage
 
Join Date: Nov 2009
Location: MS
Posts: 907
Default #12 AWG on 25 amp OPD

I cant remember the reason I was able to use a 25 amp OCPD with #12 on a motor. I think it was because of the start up amps it pulled that made it use a 25 amp.

Any help? My boss told me today " There are no circumstances where #12 should be on any OCPD larger than 20 amps"

Would love to get a free lunch.

Last edited by Voltech; 05-12-2010 at 09:24 PM.
Voltech 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 05-12-2010, 09:19 PM   #2
child please.....
 
NolaTigaBait's Avatar
 
Join Date: Oct 2008
Location: Hack City, USA aka New Orleans
Posts: 5,311
Rewards Points: 14
Default

Yeah, for a motor you can size ocp at 250% of the flc.
NolaTigaBait is offline   Reply With Quote
Old 05-12-2010, 09:20 PM   #3
Wire Ninja
 
MDShunk's Avatar
 
Join Date: Jan 2007
Location: Beautiful Cumberland Valley, in PA
Posts: 20,984
Rewards Points: 6,421
Default

Quote:
Originally Posted by Voltech View Post
I cant remember the reason I was able to use a 25 amp OPD with #12 on a motor. I think it was because of the start up amps it pulled that made it use a 25 amp.

Any help? My boss told me today " There are no circumstances where #12 should be on any OPD larger than 20 amps"

Would love to get a free lunch.
Air conditioning equipment and motor loads are two instances where he is wrong.
__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.
MDShunk is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 05-12-2010, 09:21 PM   #4
NJ-IEC
 
Magnettica's Avatar
 
Join Date: Jan 2007
Location: New Jersey
Posts: 14,387
Rewards Points: 424
Default

Tell your boss you would like a free lunch.

A/C branch circuits can be #12 THHN with 40 amp OCPD if the nameplate data says so.
__________________
Replies based on NEC 2014
Magnettica is offline   Reply With Quote
Old 05-12-2010, 09:21 PM   #5
Wire Ninja
 
MDShunk's Avatar
 
Join Date: Jan 2007
Location: Beautiful Cumberland Valley, in PA
Posts: 20,984
Rewards Points: 6,421
Default

I should say, however, that if that #12 terminates at a receptacle outlet, your boss is right. If it goes to (certain) equipment directly, then he is wrong in certain cases.
__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.
MDShunk is offline   Reply With Quote
Old 05-12-2010, 09:45 PM   #6
Senior Member
 
sparks134's Avatar
 
Join Date: Jan 2009
Location: Pittsburgh, PA
Posts: 1,118
Rewards Points: 500
Default

Tell your boss to look at table 240.4 G... Tell your boss buy you want

steak for lunch!!!
__________________
Its not just a job, it's a career!!!
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
sparks134 is offline   Reply With Quote
Old 05-12-2010, 10:20 PM   #7
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 21,255
Rewards Points: 1,498
Default

Table 310.16 shows that #12 wire is good for 25 amps at 75C. Thus using article 240.4(D & G) by the asterisk at the bottom of the table, we are not only allowed to use #12 with a 25 amp breaker but we can use #12 at 25 amps and use a 45 amp breaker.
__________________
They say I shot a man named Gray and took his wife to Italy
She inherited a million bucks and when she died it came to me
I can't help it if I'm lucky
Dennis Alwon is online now   Reply With Quote
Old 05-12-2010, 10:25 PM   #8
Les Voltage
 
Join Date: Nov 2009
Location: MS
Posts: 907
Default

Quote:
Originally Posted by sparks134 View Post
Tell your boss to look at table 240.4 G... Tell your boss buy you want



steak for lunch!!!
I wont hit him up for a steak, but I wont settle for fast food

He has an open policy in the shop. Prove him wrong and he will buy you lunch. Its a win win situation for him IMO
Voltech is offline   Reply With Quote
Old 05-13-2010, 02:54 AM   #9
Senior Member
 
JohnR's Avatar
 
Join Date: Apr 2010
Location: here
Posts: 2,416
Default

Quote:
Originally Posted by Voltech View Post
I wont hit him up for a steak, but I wont settle for fast food

He has an open policy in the shop. Prove him wrong and he will buy you lunch. Its a win win situation for him IMO

Sounds like a pretty good boss to me. He hiring?
__________________
Signed out.
JohnR is offline   Reply With Quote
Old 05-13-2010, 07:00 AM   #10
Senior Member
 
Join Date: Jul 2007
Location: FL
Posts: 925
Rewards Points: 976
Default

Here is an example of a #12 on a 45 amp breaker.

A branch circuit to a 3 HP 230 V single phase motor; all parts are listed for 75 deg C.

(Hint; articles 240.6, 310.16, 430.22(A), tables 430.52, and 430.148)
  • Table 430.148 gives a 3HP motor a full load current of 17 amps
  • 430.22(A) requires conductors be sized at 125% of full load current
  • 17 x 125% = 21.25 amps
  • Table 310.16, #12 THHN 75 deg C column = 25 amps
  • Table 430.52 allows up to 250% for the inverse time breaker
  • 17 x 250% = 42.5 amps
  • 240.4 states we can go UP to the next STANDARD size breaker
  • 240.6 would let us go up to a 45 amp breaker
  • Answer 45 amp breaker.
Roger

Roger is offline   Reply With Quote
The Following User Says Thank You to Roger For This Useful Post:
Dennis Alwon (05-13-2010)
Old 05-13-2010, 08:17 AM   #11
Moderator

 
Dennis Alwon's Avatar
 
Join Date: May 2009
Location: Chapel Hill, NC
Posts: 21,255
Rewards Points: 1,498
Default

Very nice Roger. I almost posted something similar along with my post above but I was too slack.
__________________
They say I shot a man named Gray and took his wife to Italy
She inherited a million bucks and when she died it came to me
I can't help it if I'm lucky
Dennis Alwon is online now   Reply With Quote
The Following User Says Thank You to Dennis Alwon For This Useful Post:
Roger (05-13-2010)
Old 05-14-2010, 08:13 AM   #12
Proud Navy Veteran
 
Greg's Avatar
 
Join Date: Aug 2007
Location: St. Cloud, Fl
Posts: 1,429
Rewards Points: 592
Default

The reason why you can a breaker larger than 20 on a 12 wire is because a motor circuit is the best protected circuit out there. You have overloads protecting the motor should the motor go into a fault condition, the O.L.'s will release before the breaker trips. This because of how they are sized according to code.
__________________
Memorial Day: All gave some but some gave all.
Take the time to tell a Veteran Thank You, You owe him/her at least that much. After all Freedom is not Free.
Greg is offline   Reply With Quote
Old 05-15-2010, 01:00 AM   #13
Les Voltage
 
Join Date: Nov 2009
Location: MS
Posts: 907
Default

This Back fired on me today...Went to the seafood buffet got stuffed..Then got sent out to lay out a slab. I was not worth a ***.. I sounded like my 5 year old.."my belly hurts"
Voltech is offline   Reply With Quote
Reply


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



All times are GMT -4. The time now is 11:12 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com