First time on Class 1 system

[joeyww12000]

I am helping install door lock control wiring in a jail. The conductors are Class 1,#14 and #18 stranded. How do I go about conduit fill for these types of conductors? The doors are controlled by PLC's and are 24v I think. Im just wondering how to go about fill since 360 of these conductors were put in a 3 inch conduit. They fit, but was it correct to do so? Just doesnt seem kosher to me. Nobody else seemed to care about finding out if they could do this and just did it. I want to know the correct way and how to calculate this. Thanks.

 

[bphgravity]

Following the rules outlined in Chapter 9, Tables 1, 4, and 5 would be an acceptable method.

 

[HotConductor]

Joey,

BPH is correct, however I know you are learning and you like to know details.

As soon as you know you're dealing with lv wiring look at Art. 725. In your case Class 1, look specifically at 725.3(A). This refers you to 300.17. Read the paragraph and then look at the FPN. Assuming they used EMT, look at 358.22 which directs you to Table 1, Chapter 9. This directs you to Annex C, Table C.1 for EMT. Look at THHN, 14 gauge wires, max. allowed in 3" is 364.

See how easy that was...LOL.

If you were asked this on a test though it would be a very complicated calculation.

 

[don_resqcapt19]

Having worked on these types of systems, I would strongly recommend that you look at quick pull or similar products from other suppliers. The bundles are custom as to wire size and color. When I did this kind of work we would use a bundle where wire colors matched the pigtails on the door locks and position switches. While buying the conductor this way costs about twice as much as buying single conductors, you more than make that up in reduced labor.

 

[joeyww12000]

Yeah this would be a great advantage since we are having to pull out 6 sets of doors at a time with 8 wires in each set.

 

[joeyww12000]

So you dont have to worry about derating or anything? You just go by the chart for number of conductors that can legally go in a 3" conduit?

 

[don_resqcapt19]

So you dont have to worry about derating or anything? You just go by the chart for number of conductors that can legally go in a 3" conduit?

It is my opinion that Exception 1 to 310.15(B)(2) applies and derating is not required for control conductors.

 

[HotConductor]

It is my opinion that Exception 1 to 310.15(B)(2) applies and derating is not required for control conductors.

Look at 725.51(A) & (B)

 

[don_resqcapt19]

Look at 725.51(A) & (B)

I forgot about that section. Thanks.
I would still expect that there would be no derating as I don't think you will find any continuous loads in excess of 10% of the conductors ampacity.