derate
- Thread starter wannabe
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- Windsor, CO NEC: 2017
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- Service Manager
Re: derate
Not sure what you need, hope that helped.
[ March 17, 2005, 12:20 AM: Message edited by: georgestolz ]
You derate by placing a lesser-rated breaker supplying the branch circuit.
Not sure what you need, hope that helped.
[ March 17, 2005, 12:20 AM: Message edited by: georgestolz ]
physis
Senior Member
Re: derate
Article 310 Conductors for General Wiring
Table 310.15(B)(2)(a) provides adjustment factors based on the number of current carrying conductors with reference to tables 310.16 through 310.19 .
In other words, you start with table 310.15(B)(2)(a) and find the adjustment factor you need to apply. Then you go to tables 310.16 through 310.19 (which ever applies) and find the conductor size you'll need after applying the adjustment factor.
In your case there are 12 current carrying conductors. Table 310.15(B)(2)(a) says the adjustment factor you need to apply is 50% for 10 to 20 current carrying conductors.
Your conductors will be in a raceway. Go to Table 310.16.
You need 20 amps at 50% ampacity. 10 AWG is 40 amps in the 90? C. column. 50% of that is 20 amps.
In your example you are correct. 6 twenty amp circuits in one conduit will require at least 10 AWG conductors.
[ March 17, 2005, 03:34 AM: Message edited by: physis ]
Article 310 Conductors for General Wiring
Table 310.15(B)(2)(a) provides adjustment factors based on the number of current carrying conductors with reference to tables 310.16 through 310.19 .
In other words, you start with table 310.15(B)(2)(a) and find the adjustment factor you need to apply. Then you go to tables 310.16 through 310.19 (which ever applies) and find the conductor size you'll need after applying the adjustment factor.
In your case there are 12 current carrying conductors. Table 310.15(B)(2)(a) says the adjustment factor you need to apply is 50% for 10 to 20 current carrying conductors.
Your conductors will be in a raceway. Go to Table 310.16.
You need 20 amps at 50% ampacity. 10 AWG is 40 amps in the 90? C. column. 50% of that is 20 amps.
In your example you are correct. 6 twenty amp circuits in one conduit will require at least 10 AWG conductors.
[ March 17, 2005, 03:34 AM: Message edited by: physis ]
- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: derate
Nicely put, Sam. Have an Irish brew on me.
Nicely put, Sam. Have an Irish brew on me.
al hildenbrand
Senior Member
- Location
- Minnesota
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- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: derate
Erin go Bragh!
Erin go Bragh!
bphgravity
Senior Member
- Location
- Florida
Re: derate
How did you come up with 12 current-carrying conductors?
How did you come up with 12 current-carrying conductors?
Re: derate
The process above is correct but I think Bryan is trying to get to the point that you can combine the neutrals and only have (8) current carrying conductors (6 hots and 2 neutrals) in which case 70% of 30A (#12 THHN 90 Deg C Column) is 21A. So a #12 THHN is acceptable.
-Ed
The process above is correct but I think Bryan is trying to get to the point that you can combine the neutrals and only have (8) current carrying conductors (6 hots and 2 neutrals) in which case 70% of 30A (#12 THHN 90 Deg C Column) is 21A. So a #12 THHN is acceptable.
-Ed
bphgravity
Senior Member
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- Florida
Re: derate
It is my understanding that if these were 3 multiwire branch circuits, there would be only 6 current-carrying conductors.
It is my understanding that if these were 3 multiwire branch circuits, there would be only 6 current-carrying conductors.
sparkync
Senior Member
- Location
- North Carolina
Re: derate
I'm glad to get a clearer light on this subject myself. Been trying, but seemed to be getting run around answers. Thanks again
I'm glad to get a clearer light on this subject myself. Been trying, but seemed to be getting run around answers. Thanks again
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