Ampacity Correction Code Test question

[samrmusso]

When I took the code test this it gave this question and we did not cover the steps to answer it very well in class. Can someone help me with the steps to answer these kind of questions?

Two 12-2 and two 14-2 romex are ran together. What does the ampacity need to be reduced to?

(There were multiple choice answers but I can not remember what they were)

Appreciate all your help.

 

[infinity]

Making some assumptions, that would be 8 CCC's so an adjustment to 70% of their ampacity is required. Take a look at Table 310.15(B)(3)(a).

 

[luckylerado]

.....What does the ampacity need to be reduced to?

It is important to know if it is in contact with insulation or is running through a hole that is to be sealed. Simply running together does not require an adjustment.

Have a look at 334.80.

 

[iwire]

I Simply running together does not require an adjustment.

If they run together for more than 24" derating would be required if the AHJ considers them bundled and most around here will.

 

[samrmusso]

When I took the code test this it gave this question and we did not cover the steps to answer it very well in class. Can someone help me with the steps to answer these kind of questions?

Two 12-2 and two 14-2 romex are ran together. What does the ampacity need to be reduced to?

(There were multiple choice answers but I can not remember what they were)

Appreciate all your help.

Been thinking about it some more and I don't believe there were any specifics about running through a whole or if insulated. Just the simplified question of

"Two 12-2 and two 14-2 romex are ran together. What does the ampacity need to be reduced to?

The answers were multiple choice and looked something like this:

A) Two 20 amp; two 15 amp
B) Two 16 amp; two 12 amp
C) Two 14 amp; two 10 amp
D) Two 15 amp; two 10 amp

:?
Again if anyone can show the steps it would be much appreciated.
God Bless

 

[kwired]

Been thinking about it some more and I don't believe there were any specifics about running through a whole or if insulated. Just the simplified question of

"Two 12-2 and two 14-2 romex are ran together. What does the ampacity need to be reduced to?

The answers were multiple choice and looked something like this:

A) Two 20 amp; two 15 amp
B) Two 16 amp; two 12 amp
C) Two 14 amp; two 10 amp
D) Two 15 amp; two 10 amp

:?
Again if anyone can show the steps it would be much appreciated.
God Bless

If adjustment is deemed necessary then you have 8 current carrying conductors.

310.15(B)(3)(A) adjustment factor to use is 70%

But if you have NM-B cable (which is required for new installations) you can make adjustments from the 90 C ampacity values -

so 12 AWG can be adjusted from 30 amps and 14 AWG can be adjusted from 25 amps per 90 C column.

this gives you 21 ampacity for the 12 and 17.5 for the 14.

Now the fact that 240.4(D) still limits us to 15 amps overcurrent protection on 14 AWG and 20 amps on 12 AWG there is no need to change conductor size as the adjusted ampacity of those conductors is still higher then the application calls for.

 

[charlie b]

The best of the available answers is "A." But once again, we have a test question that was written by someone who should not be writing test questions. The question asked what should the ampacity values be reduced to. Kwired gave the correct answers: 21 and 17.5. To be clear and explicit, the ampacity of the #12s is 21 amps. Separate from that issue, we are limited to protecting the #12s at 20 amps. So we will have a wire with an ampacity of 21 being protected by a 20 amp breaker. So I repeat, the question is badly written.