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
Calling all Non-US members!! (Non-US only)
by aussie240
Yesterday at 02:39 AM
Photo Upload Tutorial
by DanK
12/06/16 11:35 PM
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
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
sparkyinak 7
Trumpy 6
Who's Online
0 registered (), 218 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#79433 - 12/21/01 04:12 PM 25 amp breakers
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
Is it legal to use a 25 amp breaker with # 12 wire? if not, why do they make them?
_________________________
The Golden Rule - "The man with the gold makes the rule"

Top
2014 / 2011 NEC & Related Books and Study Guides
#79434 - 12/21/01 05:56 PM Re: 25 amp breakers
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
Yes, and it is also possible to use a 25 amp breaker on #14 wire. I am currently doing an installation with #12 wire on a 40 amp breaker.

The usual reason for this is that motor loads may have a breaker that does not correspond to the normal wire size/breaker combination. The breaker in this instance supplies short circuit & ground fault protection while the motor overload element provides the overcurrent protection. See all of 240.4

Tom
_________________________
Few things are harder to put up with than the annoyance of a good example.

Top
#79435 - 12/22/01 06:50 AM Re: 25 amp breakers
aldav53 Offline
Member

Registered: 08/22/01
Posts: 547
Loc: Chandler, AZ USA
Tom,
Thanks for replying-
What do you mean when you say the motor leads have a breaker? Are you talking about the auto overload shut-off built into the motor? How can it be legal with a new installation to put a 40 amp breaker using #12 wire, even though the motor leads are smaller. Am I wrong here?
_________________________
The Golden Rule - "The man with the gold makes the rule"

Top
#79436 - 12/22/01 07:16 AM Re: 25 amp breakers
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
Al,

Motor loads can have a very high inrush current when first turned on. A motor that only uses say, 10 amps can draw 60 or 100 for a short time when first turned on. So, it is sometimes necessary to use a larger breaker to allow the Motor to start, and the wire is basically sized to the running load of the motor.

Take a look at 430-52 and Table 430-152 in the 1999 NEC

Bill

Top
#79437 - 12/22/01 07:30 AM Re: 25 amp breakers
electure Offline

Member

Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
Please note that if not a motor or A/C load, the #12 is not legal. You would need to use #10

Top
#79438 - 12/22/01 07:41 AM Re: 25 amp breakers
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
Al,

Again, take a look at 240.4 and table 240.4(G). There are quite a few instances where the standard wire to breaker size relationship is not what you would normally expect.

Tom
_________________________
Few things are harder to put up with than the annoyance of a good example.

Top
#79439 - 12/22/01 10:51 AM Re: 25 amp breakers
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
One thing I have found a use for a 25 amp breaker is A/C, and for those units the Breakers are suppose to be HACR RATED, a lot of service revamps I do, that have air conditioning is to check the name-plate on the unit and it will tell you what size breaker to use and have found a lot of units that call for a 25 amp breaker.
When doing the revamp I find a lot of 30 amp breakers used inplace of the 25 amp breakers, thats about the only place I have ever used them.
The only people that have them on the shelf is the big Orange place, and they are usually Murray or basically a Siemens. I am sure every breaker manufactureer makes them just not a big demand for them.

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