Derating situation

[joeyww12000]

Heres the deal, I have conductors of 18awg and 14awg to be pulled in a 1 1/4" pvc conduit. These conductors will be feeding door locks for jail cell doors. Problem is they should have been in at least 4 seperate conduits for this application but we have what we have, there not in the slab and its to late. Anyway the total of the conductors is 24 14awg and 32 18awg, totalling 56 conductors in this 1 1/4" PVC conduit. Besides being hell to pull, how do I figure derating on this? Does the load being served have any impact? There isnt a constant load, only when doors open and close.

 

[Pierre C Belarge]

What is the source of supply for the 18 AWG conductors? (is it a Class 2 transformer)

What is the source of the supply for the 14 AWG conductors?


I am curious why you are installing the conductors of these particular sizes in the same raceway. I am thinking you have power and Class 2 conductors in the same raceway, which is not a permitted type of installation.


If you do not have Class 2 conductors mixed with power conductors, you can possibly use Exception #1 of 310.15(B)(2)(a). It all depends on what source(s) that are powering the conductors.

 

[iwire]

I agree with Pierre, it sounds like you are in for more trouble then derating.

 

[don_resqcapt19]

I don't think that derating applies to these conductors as it is my opinion that none of the conductors are covered by Articles 210, 215, 220 or 230. I also really doubt that the power supply is a Class 2 power supply.

 

[Minuteman]

Are the conductors rated the same? Are the 18's and 14's all THWN rated 600 volt?

 

[Minuteman]

300.3(c)(1)

 

[iwire]

Are the conductors rated the same? Are the 18's and 14's all THWN rated 600 volt?

That alone is not the only NEC section he may need to deal with.

 

[Minuteman]

Of course, I was only addressing the separate systems issue.

Sounds to me like he may need to increase the conductors size to some unrealistic value, as we do not know his amperages. Also, above 41 CCC's is 35%, but how many of his 56 wires are CCC's? We don't know.

The stark reality is, a change order should be issued to get him his other conduits in the slab.

 

[joeyww12000]

Thanks for the help guys. This is my first low volt installation and Im working with another electrician who has done a couple of installations now. This is the first job ever for our foreman and he's leaving it up to us, but he installed the conduit in the slab for what is now, our problem low volt installation. Im not up to date on any NEC for this low volt install, thats why Im asking, but looks like I need to get back to you after we have our next meeting, so I can ask more thorough questions. Thanks.