gaelectric
Senior Member
- Location
- Highlands Ranch, CO
Why in the world did they change the nice clear table 310.15(B)(7) from the past code book to the 83% thing? At least they could have left the table in addition to the added verbiage.
Changes to 2014 310.15(B)(7)
- Thread starter gaelectric
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fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
to make it harder to use -- on purpose
to make it harder to use -- on purpose
Because electricians wiring non-residential buildings would come upon the table and use it, when it was reserved for only the conductors that supply the complete load of a residence. Electricians would also apply the table to partial residential loads such as a feeder to one of several subpanels.
to make it harder to use -- on purpose
Because electricians wiring non-residential buildings would come upon the table and use it, when it was reserved for only the conductors that supply the complete load of a residence. Electricians would also apply the table to partial residential loads such as a feeder to one of several subpanels.
- Location
- Illinois
- Occupation
- retired electrician
I don't think getting rid of the table will have any effect on those issues.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
On the contrary, I think that a good number of people who will have their eye caught by the old table will not read closely enough to find the new 83% reference in the text. Or at least will be forced to read it in context if they do.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
This was done to correct the issue of ampacity correction when required such as SE cable through insulation. Under the old rules there was no way to make adjustments as the text and table simply said to use a certain conductor for a given service size, regardless of possible required adjustments for conditions of use. By using a formula it now allows and if in fact may require ampacity adjustment for certain conditions.
For example, a 200 amp service (or feeder) will need an ampacity of 166 amps (200 X .83). That would be a 4/0 AL SE cable-just like previous editions. But now if that SE cable is buried in insulation it will need to be used at the 60 degree value per Art 338. That would in turn require a 250 AL SE cable. They have even included a new FPN to alert you to possible ampacity adjustments.
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