I still at times have trouble deciding on the correct wire size and breaker size for panels and other installations. What is the best way to re-learn this. I often come up with different sizes than one of my co workers. Not always, just sometimes and I would like to eliminate that. Thank You, Steve Wiese.
Sizing conductors and breakers.
- Thread starter steve61
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Start with the size of the load. So if you need to install a 100 amp panel then go from there. You'll need a 100 amp feeder, look up the conductor size in 310.16. You already know that you need a 100 amp OCPD.
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
Do you have an example of a time when you and your coworker got a different wire / breaker size?
Are you both starting with the same load?
Are you both starting with the same load?
solarken
NABCEP PVIP
- Location
- Hudson, OH, USA
- Occupation
- Solar Design and Installation Professional
If referring to dwelling units, there is a difference in sizing between main load centers and sub-panels, so maybe some of the differences are due to the nuance. In most cases Service conductors can be sized per 310.12 at 83% of the service rating, where a subpanel cannot.
That's correct. It is based on "load diversity"...if you look at the house as a whole, the load will vary enough to allow some latitude in conductor sizing. That load diversity might not be present in a subpanel.