lets say u are running 440 volt 3 phase equipment.now inside conduit u run 21 wires all thhn #12 stranded these wires are going to 440 volt 3 phase motors do they get derated just like any other wire and if you get to a j-box and cut them into u now have 42 wires in that box would u then use a different derating # or would u still stay with 21 article 310-8{a} hope this makes since to u guys

MAY THE SUN SHINE ON YOUR FACE IN THE MORNING AND YOU AWAKE WITH A SMILE

SORRY FOR THE MIX UP I am looking in article 310 and in the 96 code book on page 196 u have 8 Adjustment factors then u have {a} at that point it shows 21-30 wires if I have 21 then I would derate them to 45 percent.Now i go to a junction box i cut them into at that point I now hve 42 wires in the j-box would I derate those wires using 41 or more which would be 35 percent or even though I did cut them in the j-box it would still be 21 wires hope this helps

MAY THE SUN SHINE ON YOUR FACE IN THE MORNING AND YOU AWAKE WITH A SMILE

Re: Derating and adjustment factors#77311 05/20/0108:42 PM05/20/0108:42 PM

oh, ok,,, the 'pipe fill' bears derating, 30A(T310-16) x 45%(T310-15(b)(2))= 13.5A, so next 240-6 would be 15A

the 'jb' needs only to meet fill requirements. As the wires have been cut, instead of passing thru, i beleive your fill requirements are doubled. 21 x 2.25= 47+ cubes 42 x 2.25= 94.5 cubes

ok doc?

Re: Derating and adjustment factors#77312 05/21/0112:15 AM05/21/0112:15 AM

Table 310-16: #12 THHN cu @ 90 degrees = 30 amps. Table 310-15(b)(2)(a): Number of current carrying conductors: 21-30 = 45% Multiply 30 amps x .45 = 13.5 Amps

This is for 30 degrees C Ambient Temperature. If higher than 30 C, adjust maximum amperage of 310-16 [30 amps for #12 THHN cu] by the corection factor, then derate for 21-30 conductors. If the loads are LCL, then derate the maximum amperage [30 amps for #12 THHN cu] by 80%, making it 24 amps - then apply temperature corrections [if any], then finally derate for 21-30 current carrying conductors.

The conductors in the raceway [conduit] are the ones being derated. Box fill is another area.

Steve had already pointed out the corrected value of 13.5 amps - using 15 amp OCPD, so this message is just to explain how he came up with that figure.

Scott SET

Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!

Re: Derating and adjustment factors#77313 05/21/0105:52 AM05/21/0105:52 AM

Guys, Remember that with motor circuits the dreated ampacity of the conductors only has to equal 125% of the motor current as shown in Tables 430-147 through 430-150. It does not have to equal the rating of the branch circuit short-circuit and ground fault protection device. Don(resqcapt19)

Don(resqcapt19)

Re: Derating and adjustment factors#77315 05/21/0104:18 PM05/21/0104:18 PM

Another reminder that doesn't apply to this post, but seems to be a common oversight, you cannot round up to 15 amps if the conductors are part of a multi-outlet branch circuit that supplies receptacles for cord and plug connected portable loads.

Tom

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