Grounding an aluminum heater assembly

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CaliforniaMike

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Hello,
I recently was asked to look at a heating assembly that is used in a production plant. The original request was to evaluate the strain relief and propose a new way to assemble the cable to increase the life of the cable. A quick look revealed that there is no ground wire to the assembly. This is a 115 VAC heated core that pulls about 0.6 A nominal. Operators are in contact with the assembly while live...

My question relates to the proper way to attach a ground lead to the assembly. There are two halves; each will need to be grounded. However, they are thin. I am tempted to use a #10 stainless screw and a SS external lock washer. However, these are not listed parts. On top of this, the assembly body is aluminum. I am not sure where this assembly would fall under NEC. What are my options? Can anyone suggest a listed, but very compact grounding system for a device that only pulls 0.6 amps?

Thanks,

Mike
 
The actual heaters are UR listed. The aluminum assemblies that the heaters are siliconed to are custom made in their shops. The heating is a flexible silicone heater.
 
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If the heaters are screwed into a metal assembly, i don't see how they could get any more bonded.

This is a proper means of bonding in machines covered by NFPA79.

8.2.2.3.1 Machine members or structural parts of the electrical
equipment shall be permitted to be used in the equipment
grounding circuit provided that the cross-sectional area of
these parts is at least electrically equivalent to the minimum
cross-sectional area of the copper conductor required.
8.2.3 Continuity of the Equipment Grounding (Protective
Bonding) Circuit.
8.2.3.1 The continuity of the equipment grounding (protective
bonding) circuit shall be ensured by effective connections
through conductors or structural members.
8.2.3.2 Removing a device shall not interrupt the continuity
of the equipment grounding (protective) circuit.
8.2.3.3 Bonding of equipment with bolts or other identified
means shall be permitted where paint and dirt are removed
from the joint surfaces
Click to expand...
 
Oops.

Sorry if I was not clear. The assembly to which the heating element is mounted is not gounded and this is the central issue to my question.

The complete assembly is about the size of a hocky puck. It is aluminum and has a flexible electrical cable running to it so that it can be picked up and moved around within the limits of the length of the cable. Currently, the cable has hot and neutral (22 AWG), and two thermal couple wires. No ground. I was asked to look at the cable because this cable has a history or broken power conductors.

From your posting, it looks like 8.2.3.3 and 8.2.2.3.1 may point to my answer. By this standard, a tapped #10 SS, or, or probably smaller, screw would certainly have a larger cross sectional area than the equivelent current carrying conductor would warrent.

I suppose that I can then tie this into a ring terminal crimped to a #18 AWG (250.112E) ground wire and call it grounded.

This said, I am still a little unclear about the copper-lug-aluminum assembly interfaces. For larger stuff, I have always just used a CU-AL listed lug, noalox, proper torque, and moved on.

Thanks for the help, I spent most of my formative years on larger stuff and grounding for a 0.6 amp circuit is a bit of an outlier for me.

Mike
 
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