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 Search this Thread Display Modes
Old 02-16-2008, 01:13 AM   #1
Member
 
Join Date: Feb 2008
Posts: 39
Rewards Points: 25
Default inverse breakers

seems to be alot of questions about these specialty bbreakers where can i find them in the code book

john salyards 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!

Old 02-16-2008, 01:45 AM   #2
Registered Member
 
Join Date: Feb 2008
Location: Atlanta, Ga/Hamilton, Al
Posts: 4,868
Rewards Points: 2,000
Default

Quote:
Originally Posted by john salyards View Post
seems to be alot of questions about these specialty bbreakers where can i find them in the code book
They are defined in article 100. They are mentioned in the motor over current table. Other overcurrent protection articles can be found in 240. But overall, the code doesn't say much about them. They would be specified in a set of plans, more than a code article.

But if you don't know, an inverse-time breaker is one whose trip time is inversely proportional to the amount of overcurrent. That is, the larger the overcurrent, the faster it trips. As opposed to instantaneous-trip.

You want inverse-time on circuits that expect to have a slight overload for a short period of time, like motor circuits.

InPhase277

InPhase277 is offline   Reply With Quote
Old 02-16-2008, 07:44 AM   #3
Senior Member
 
brian john's Avatar
 
Join Date: Mar 2007
Location: Leesburg, VA
Posts: 25,141
Rewards Points: 2,000
Default

All molded case circuit breakers are INVERSE TIME circuit breakers (OK 99% of them). All this means is the higher the current the faster the CB trips.

Circuit breakers utilized in typical branch circuit wiring are thermal magnetic devices. That is thermal is the long time/overload portion, higher the current the faster the circuit breaker operates for over loads.

For thermal Such as a 20 am CB may carry 300% (60 amp) for 30 seconds
200% (40 amps) for 90 seconds
110% (22 amps) for days
All times are estimates/guesses as I do not have time curves available at this time, (there are in the office).

For Instantaneous Instantaneous occurs at multiples above 400% typically and operates on the same principle, the higher the current the faster the CB trips.

Inverse only CBs are normally part of a motor control stater or motor control center where the thermal (long time/overload) protects the motor against overloads, the inverse time is for fault protection and is sized to permit the motor to start (starting currents are typically 4-6 times). Inverse CBs have settings from 4-12 times normally that is for a 20 amp CB 80 to 240 amps.
brian john is offline   Reply With Quote
The Following User Says Thank You to brian john For This Useful Post:
Dennis Alwon (03-17-2011)
Old 10-06-2009, 01:04 PM   #4
Junior Member
 
Join Date: Oct 2009
Location: Isreal
Posts: 1
Rewards Points: 10
Default

What is the smallest-size fixturewire permitted in the NEC is ........AWG?
Esakoh is offline   Reply With Quote
Old 10-06-2009, 01:39 PM   #5
Senior Member
 
Join Date: May 2007
Location: SC.
Posts: 9,431
Rewards Points: 2,194
Default

Quote:
Originally Posted by brian john View Post
All molded case circuit breakers are INVERSE TIME circuit breakers (OK 99% of them). All this means is the higher the current the faster the CB trips.

Circuit breakers utilized in typical branch circuit wiring are thermal magnetic devices. That is thermal is the long time/overload portion, higher the current the faster the circuit breaker operates for over loads.

For thermal Such as a 20 am CB may carry 300% (60 amp) for 30 seconds
200% (40 amps) for 90 seconds
110% (22 amps) for days
All times are estimates/guesses as I do not have time curves available at this time, (there are in the office).

For Instantaneous Instantaneous occurs at multiples above 400% typically and operates on the same principle, the higher the current the faster the CB trips.

Inverse only CBs are normally part of a motor control stater or motor control center where the thermal (long time/overload) protects the motor against overloads, the inverse time is for fault protection and is sized to permit the motor to start (starting currents are typically 4-6 times). Inverse CBs have settings from 4-12 times normally that is for a 20 amp CB 80 to 240 amps.
Yep, I have Table 430-152 Inverse Time Breaker marked "regular breaker". So as to not be confused.
John Valdes is offline   Reply With Quote
Old 03-17-2011, 06:40 AM   #6
Junior Member
 
Join Date: Mar 2011
Location: Indonesia
Posts: 1
Rewards Points: 10
Default

found these explanation from google. Clear & usefull,
Thanks !!

bee77 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Arc Fault breakers waco General Electrical Discussion 2 11-13-2008 05:17 AM
Breakers popping skrappi69 General Electrical Discussion 26 12-10-2007 09:35 PM
Breakers not tripping guschash General Electrical Discussion 7 08-27-2007 10:59 AM
Backstabbed breakers. MDShunk General Electrical Discussion 8 08-14-2007 06:09 PM
dc fuses/breakers ILSS NEC Code Forum 1 07-19-2007 11:40 AM


All times are GMT -4. The time now is 07:51 PM.


Copyright 2006-2014 Escalate Media LP. All Rights Reserved
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com