ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

Topic Options
Rate This Topic
#89645 - 10/12/04 01:32 PM Maximum Load on 15A
mustangelectric Offline
Member
Registered: 02/08/04
Posts: 494
Loc: Bentonville, AR
Is it not required to limit the load on a 15A breaker? I have a 11A load on a Condensing Unit that is being fed by a 15A brkr...I am thinking this is too small.

Any replies will be greatly appreciated.

regards

mustang
_________________________
Electricity has no respect for ignorance!
Top
2017 / 2014 NEC & Related Books and Study Guides
#89646 - 10/12/04 01:37 PM Re: Maximum Load on 15A
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
A 15 amp breaker is allowed to be loaded 100% up to 3 hours, longer than 3 hours the load may only be 80% which is 12 amps.

11 amps on a 15 amp breaker is fine.

However you said this is a condensing unit, the label should say what size overcurrent protection to use.



[This message has been edited by iwire (edited 10-12-2004).]
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts
Top
#89647 - 10/15/04 04:42 PM Re: Maximum Load on 15A
Steve T Offline
Member
Registered: 02/14/01
Posts: 306
Loc: Oak Park, IL, USA
The breaker for a condenser is only short-circuit protection which can be 175% of the rated load current or branch circuit selection current, whichever is greater. If that's not enough to allow the compressor to start then you can go up to 225%. 11x1.75=19.25 an 11X2.25=24.75.
Top
#89648 - 10/16/04 10:28 AM Re: Maximum Load on 15A
Ryan_J Offline
Moderator
Registered: 08/19/03
Posts: 1374
Loc: West Jordan, Utah, USA
Steve: I agree with Bob on this. I typically just apply
Quote:
440.22(C) Protective Device Rating Not to Exceed the Manufacturer’s Values. Where maximum protective device ratings shown on a manufacturer’s overload relay table for use with a motor controller are less than the rating or setting selected in accordance with 440.22(A) and (B), the protective device rating shall not exceed the manufacturer’s values marked on the equipment.


Not that the math is that difficult, but in my opinion, why go through it?
_________________________
Ryan Jackson,
Salt Lake City
Top
#89649 - 10/16/04 10:37 AM Re: Maximum Load on 15A
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
You can not "do the math" you must use the Manufacturer’s Values.

Anything higher than that and you have tossed out the UL listing.
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts
Top
#89650 - 10/16/04 10:52 AM Re: Maximum Load on 15A
Ryan_J Offline
Moderator
Registered: 08/19/03
Posts: 1374
Loc: West Jordan, Utah, USA
That too
_________________________
Ryan Jackson,
Salt Lake City
Top
#89651 - 10/16/04 02:04 PM Re: Maximum Load on 15A
SteveMc Offline
Member
Registered: 02/05/04
Posts: 62
Loc: Rock Hill, SC
#14 awg wire ok?
Top
#89652 - 10/17/04 10:11 AM Re: Maximum Load on 15A
Ryan_J Offline
Moderator
Registered: 08/19/03
Posts: 1374
Loc: West Jordan, Utah, USA
Absolutley #14 is OK. If the load is 11 amps, all you need is a conductor that satisfies the load. You can then put on the highest fuse or breaker allowed by the manufacturer and still be OK. For example, if the load was 11 amps and the nameplate says maximum OCPD is 40 amps, you may install a 40 amp breaker and run #14 for the circuit.

See 240.4(D) which points you to 240.4(G), then go to part IIIof article 440 for A/C units.

Quote:
III. Branch-Circuit Short-Circuit and Ground-Fault Protection
440.21 General.
The provisions of Part III specify devices intended to protect the branch-circuit conductors, control apparatus, and motors in circuits supplying hermetic refrigerant motor-compressors against overcurrent due to short circuits and grounds. They are in addition to or amendatory of the provisions of Article 240.
_________________________
Ryan Jackson,
Salt Lake City
Top

Member Spotlight
Member Since: 02/23/13
Posts: 204
New in the Gallery:
SE cable question
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box


Who's Online
0 registered (), 67 Guests and 10 Spiders online.
Key: Admin, Global Mod, Mod
 
New in the Gallery:
SE cable question
 
Top Posters (30 Days)
Admin 47
HotLine1 43
gfretwell 19
Ruben Rocha 12
Trumpy 9
 
Newest Members
KrmtFrg, Stack, Scotto, Freecrowder, clee512

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals