80 percenyt Conduit fill ?

[james_mcquade]

Hi everyone,

I designed a control system for a company in which i stated (2) conduits to an operator control panel.
The system is 24 volts dc and all conductors are less than 1 amp.
#1 had (90) #14 THHN conductors including spares and a 2" rigid conduit.
#2 had (4) instrumentation cables of approx. 1/4" diameter and a 1 1/4" rigid conduit.

the budget was tight so i did my best to keep the system cheap, but i had to design it correctly.

i went back today as the final debug of the system was being done and found that
conduit #1 was run with (87) #14 thhn wires run in a 1 1/4" rigid conduit not the 2" i specified.
conduit #2 was also 1 1/4" as specified.

Ok, i admit that many contractors would probably pull 90 wires in a 1 1/2" conduit and be ok with it,
but 87 wires in a 1 1/4" conduit.

when i asked the electrical contractor how he got around the conduit fill rule, he said that because
the system was 24 volts and less than 1 amp, he could use 80% of the fill for the conduit.
He did not cite book, chapter & verse but would be happy to for a fee.

My question is, have i missed something that would allow him to use 80% of the fill capacity?
If so, please tell me the code.

Thanks in advance,
James

 

[xformer]

Look at 344.22

 

[james_mcquade]

Thanks for the reply, i thought i was correct.
If i am still wrong, please jump in with details.

Oh, by the way, i just got off the phone with the same customer.
He has now added even more sensors to his system and has ran out of wires.
I had 20% spares and he now needs 20 more.
He forgot about a machine process that was off to the side.

regards,
james

 

[infinity]

How are these conductors classified? If they covered under Article 725 is it possible that the 40% fill might not apply? Here's what is says for Class 1 conductors:

725.51 Number of Conductors in Cable Trays and Raceway, and Derating.
(A) Class 1 Circuit Conductors. Where only Class 1 circuit conductors are in a raceway, the number of conductors shall be determined in accordance with 300.17. The derating factors given in 310.15(B)(2)(a) shall apply only if such conductors carry continuous loads in excess of 10 percent of the ampacity of each conductor.

 

[erickench]

How are these conductors classified? If they covered under Article 725 is it possible that the 40% fill might not apply? Here's what is says for Class 1 conductors:

If they're 24 volts DC then they may not be class 1. They could be class 2. Look at NEC table 11(B) in chapter 9. As for the conduit fill I think the contractor is pulling your leg on this one. NEC 300.17 applies to all Class 1,2, & 3 conductors as per NEC 725.3(A). But if there is an inspection authority and he's willing to accept the installation as is then there shouldn't be any problem.

 

[stevenj76]

Careful with the 80%... if it has to be fire-caulked, max is 60%.