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#161994 04/11/07 11:58 AM
Joined: Nov 2002
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RSmike Offline OP
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Is running a shielded twisted pair communications cable (CAN-bus operating at 5-24vdc) along with a SO cord 18/3 (operating at 3A - 120VAC) inside the same liquid tight flexible nonmetallic conduit (LFNC) a legal installation with respect to NPFA70-2005? With respect to NPFA79-2007?

Put on your thinking caps gentlemen,

RSLater,
RSmike

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RSmike #162001 04/11/07 05:05 PM
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SO Cord can not be installed in a raceway.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
iwire #162011 04/11/07 07:05 PM
Joined: Oct 2006
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Unless all conductors, not cables, are rated for the maximum voltage in use within the raceway, then this type of installation isn't permitted. My question would be how these circuits are separated at the ends of the liquid-tight since any approved enclosure would have separate high and low-voltage compartments?

I'd go with the shielded communications cable routed outside of the liquid-tight and run THHN, etc. inside.


---Ed---

"But the guy at Home Depot said it would work."
EV607797 #162012 04/11/07 07:14 PM
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JBD Offline
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Originally Posted by EV607797
My question would be how these circuits are separated at the ends of the liquid-tight since any approved enclosure would have separate high and low-voltage compartments?


There are many industrial enclosures which contain PLCs and/or drives that use CANBUS for communications that do not have separated LV compartments.

This sounds like a Class 1 or Class 2 application although <24V communications circuits are not always "power limited".

Last edited by JBD; 04/11/07 07:17 PM.
JBD #162021 04/11/07 09:55 PM
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Communications wiring and Power wiring are not permitted in the same raceway I don't care what the insulation ratings are. Article 800 Section 800.133 NFPA70 2005 Edition.


George Little
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RSmike Offline OP
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Unless I missed it I also don't see NPFA70 allowing this or it's not specifically stated.

However, I read NPFA79 13.1.3 as allowing this; comments?

RSLater,
RSmike


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JBD Offline
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Originally Posted by George Little
Communications wiring and Power wiring are not permitted in the same raceway I don't care what the insulation ratings are. Article 800 Section 800.133 NFPA70 2005 Edition.


Here we go with terminology.

CAN bus is normally used for interconnecting automation devices which is is probably a 725 remote-control and signalling application. 725.55(D) and 725.55(E) have provisions for mixing Class 2 and Class 3 circuits with other wiring.

Article 800 is for "central station systems" like telephones. However, 830 address networks so 830.133(A)(1)(d) Excpt #1 may be applicable.


JBD #162038 04/12/07 10:11 AM
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RSmike Offline OP
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725.55(D)(2)a - makes me a happy person.

What about SO cord in LFNC? Why is this not allowed? It terminates so well into the operator interface terminal device I'm powering. THHN is cheaper so I'll probably do that.

RSthanks,
RSmike

RSmike #162047 04/12/07 11:58 AM
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George isn't class 1 OK in the raceway with the circuit(s) it controls?
I agree class 2/3 is not.
I suppose the real question is whether CanBus is a class 1 compliant wiring method


Greg Fretwell
Joined: Jan 2004
Posts: 1,507
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Greg- The original post only said Communication cable which put me in Article 800. I don't really know what CanBus is and maybe you are correct. Don't sound to me like 725 is even involved. Maybe I don't know what I'm talking about. The Scope of 800 is Communication Circuits and so that's where I went. Straighten this old man out smile


George Little
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