Tray continuous ground conductor

[EngSnow]

Our contractor installed a multiconductor cable in a tray. I was told per NEC, we have to increase size of existing bare tray grounding cable because it's smaller than our newly installed cable equipment ground. Is that correct? Each cable in this tray has its own equipment ground.

 

[7anoter4]

I am afraid the cable tray has to withstand the presumed short-circuit current. See NEC 2014 Art.250.96 A) Metal raceways, cable trays,etc.... ...with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them.

 

[EngSnow]

Per 250.96(A): " Cable trays.....that are to serve as equipment grounding conductors...". The cable tray in question is NOT to serve as equipment grounding conductor. Is there any other reference in the code that addresses this issue?

 

[7anoter4]

I agree the cable tray does not have to be bonded but only connected to equipment grounding conductor. If this cable tray contains service cables it has to be grounded as per 250.80 Service Raceways and Enclosures.
250.86 Other Conductor Enclosures and Raceways means that any cable tray has to be connected to the equipment grounding conductor -excepting [see the 4 required exceptions for pos.1 exceptions and 2 or 3- if any ].
In this case only part of the ground fault current will flow through the cable tray. If you can appreciate how much will be this part you may verify if the cable tray will withstand this.
From our experience in power stations-we prefer to comply the code like all the current will flow through cable tray only.

 

[EngSnow]

7anoter4, thanks for your reply. I still do not see the cable tray connection to grounding conductor requirement. This section you refer to (250.86) is for enclosures and raceways (conduits), not cable tray.