Grounding Overhead Cable Tray Outdoors

[livewire9]

Is it standard practice to ground both side rails of aluminum cable tray at support locations? I am designing cable tray that is carrying control cables from a new sub over to an old sub where there is an existing control house with available panel space. The cable tray is run vertically up to 25' from the new yard, over, and down into the old yard on custom steel structures.

Christopher Renedo, P.E.
ESC Engineers
Ft. Collins, CO

 

[7anoter4]

NEMA VE-2
4.8 BONDING TO BUILDING STEEL AND EARTH
"Metallic cable trays shall be bonded to building steel and earth as supplemental grounding for ground fault protection and signal grounding (“noise” prevention). The tray shall be bonded to building steel and earth, at least every 60 ft. This is only required when the cable tray system is not inherently bonded (connected) to building steel and earth through metallic support systems."

 

[waross]

The petro-chemical industry holds to more stringent codes. It is common to run a grounding conductor in the tray and bond it to one side rail every 40 or 50 feet. It is also regularly connected down to the ground grid. I don't have the specs for the exact footage at hand.
This despite the fact that the Canadian Electrical Code would not require any grounding cable as the trays are mounted on grounded steel supports.
Note: When more than one tray is run parallel it is common to install the runner cable in one tray only. At every connection to the side rail, daisy chain jumpers ground one side rail of each of the other parallel trays. A connection is generally taken down to the ground grid at this point also.
Expansion joints may have flexible jumpers across the joints on each side on one spec, and no jumpers on the next spec as long as the runner cable is connected and the daisy chain jumpers installed within a specified distance on each side of the expansion joints.
As an example: If the spec calls for grounding within 20 feet then the connections may be 40 feet apart but must be within 20 feet on each side of an expansion joint.
Typically the tray will be clamped tightly to the supports once, midway between expansion joints. All other connections will be guide type which will allow the tray to expand and contract towards the expansion joints. There is a clip on the market which will clamp in one orientation and guide if installed upside down.

Bill
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"Why not the best?"
Jimmy Carter

 

[livewire9]

Thanks for the feeback, gents! Very helpful.

Christopher Renedo, P.E.
ESC Engineers
Ft. Collins, CO