AWM cables in NFPA 79 and NEC

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lukefeil

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Lake Orion, Michigan
Hello Everyone!

I stumbled across a little code questions that gets me through the NEC and the NFPA79. On an industrial HVAC system for a climate control testing chamber the supplier used AWM style cable (not dual rated). This cable is installed in bundles around the machine, fastened with cable ties and used for low voltage control signals only.

I believe these cables should be run in a raceway. The supplier believes as low voltage they're excempt from NEC. Here my current problem:

1) I know that NEC applies to all wiring, independent of voltage
2) Article 725 incudes some excemption for "low voltage" wiring in regards to Article 300
3) But 725.46 tells me that Class I has to comply with Part I of Article 300 (which is <1000V so basically the excemption from Article 300 is void) and with the wirig methods from chapter 3
-> AWM style cable is generally not permitted, as it is not an NEC described wiring method.

Now we are leaving NEC and go to NFPA 79.

1) in 2007 all AWM style cable was banished from industrial machines, as the AWM cable should only be used inside a listed equipment
2) in 2018 the AWM style cable was re-introduced in 12.9.2, and it's use permitted under certain conditions
3) 12.9.2(3) tells us that AWM style cable can be used if it complies with Section 12.2 through 12.6 (and some modifications)
4) without verifying the stranding, gauges, etc. I look at 12.6.4.3 that tells me that the cables need to be installed according to chapter 13
5) Chapter 13, section 13.1.6 "Cables" simply says that "exposed cables installed along the structure of the equipment or system or i the chases of the mcahinery shalle be peritted and shall be installed to closely follow the surface and structral members of the machiner"

The last point (5) gives me my big headache - it generally states that cables are permitted in exposed installation. Knowing that NEC applies independent of NFPA 79, I guess the authors of NFPA 79 relied on the provisions in Chapter 3 of NEC to describe the individual requirements for each cable assembly type. But as I got AWM style cable it is not referenced in NEC - so no further requirements.

Am I wrong (the supplier can install the AWM cable unprotected around the machine), right (the code has a flaw) or do I oversee something?

Best Regards,
lukefeil
 
most AWM wire is also listed as MTW.

AWM is still allowed by NFPA79. See 12.9.2.

the NEC is an installation standard, not a machine standard. if the wiring is part of the machine it can't be part of the installation.
 
lukefeil said:
Hi Bob,

Thank you for your reply, but I talk about a multi conductor cable, also I mentioned that it has no dual rating...

Best regards,
lukefeil
Click to expand...

I am not sure such a device even qualifies as something that would be covered by NFPA79.

Are you claiming the device is not listed and thus the exemption for using AWM does not apply?

12.9.2 Appliance wiring material (AWM) shall be permitted
under any of the following conditions:
(1) Where part of an assembly that has been identified for the
intended use
(2) Where the AWM has been identified for use with approved
equipment and is used in accordance with the
equipment manufacturer’s instructions
Click to expand...

It seems to me that merely by using it the equipment manufacturer has identified it as appropriate.
 
Hi Bob,

The "device" is a complete machine with industrial control panels, motors, sensors, ...

It is not listed and the AWM cable is used for the field interconnection between panels and sensors.

In my code reference I check for point (3) which permits use under certain circumstances.

Best regards,
Lukefeil
 
lukefeil said:
Hi Bob,

The "device" is a complete machine with industrial control panels, motors, sensors, ...

It is not listed and the AWM cable is used for the field interconnection between panels and sensors.

In my code reference I check for point (3) which permits use under certain circumstances.

Best regards,
Lukefeil
Click to expand...

I still don't know that NFPA79 is the appropriate standard for this piece of equipment.

1.1* Scope.
1.1.1 The provisions of this standard shall apply to the
electrical/electronic equipment, apparatus, or systems of industrial
machines operating from a nominal voltage of 600
volts or less, and commencing at the point of connection of
the supply circuit conductors to the electrical equipment of
the machine.
Click to expand...

Is this an industrial machine? I am not sure how you would shoehorn it into this defintion of what an industrial machine is.

3.3.54 Industrial Machinery (Machine). A power-driven machine
(or a group of machines working together in a coordinated
manner), not portable by hand while working, that is used
to process material by cutting; forming; pressure; electrical, thermal,
or optical techniques; lamination; or a combination of these
processes. It can include associated equipment used to transfer
material or tooling, including fixtures, to assemble/disassemble,
to inspect or test, or to package. [The associated electrical equipment,
including the logic controller(s) and associated software
or logic together with the machine actuators and sensors, are
considered as part of the industrial machine.
Click to expand...

On an industrial HVAC system for a climate control testing chamber
Click to expand...

I don't see how a climate control testing chamber or an HVAC system qualifies as an industrial machine. What material is being processed?
 
Hi Bob,

I would count this in the "test "category, as this is one station in the whole process.
Anyway, turns out the cable has CL3R/CMG rating, which directs me to Article 725.

Thank you for your involvement!

Best regards,
Lukefeil
 
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