Bonding to cable tray

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edavis2293

Member
Location
Houston, Texas
It is my opinion, and several others, bonding is not required from cable tray to utilization equipment when using type TC-ER cable even in hazardous locations. The cable tray system is strictly a support system and is not being used as an equipment grounding conductor. If there is an NEC section that states a bonding jumper is required, I would appreciate you letting me know where that is. Thanks.
 

RUWired

Senior Member
Location
Pa.
I think 250.90 would cover the requirement to bond the cable tray to all equipment and each other reguardless of the wiring method in the tray.

Rck
 

RUWired

Senior Member
Location
Pa.
I read that and it says pretty much the same thing but it adds "that are to serve as grounding conductors" and thought that it could be argued that its not being used in that manner, although the metal tray qualifies as an egc.

Rick
 

edavis2293

Member
Location
Houston, Texas
I read that and it says pretty much the same thing but it adds "that are to serve as grounding conductors" and thought that it could be argued that its not being used in that manner, although the metal tray qualifies as an egc.

Rick
This is our arguement; it is not being used as an equipment grounding conductor, therefore, it doesn't require additional grounnding or bonding.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired) DINOSAUR
Would 392.7 not cover that ?

392.7 Grounding.
(A) Metallic Cable Trays. Metallic cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250.
 

RUWired

Senior Member
Location
Pa.
This is our arguement; it is not being used as an equipment grounding conductor, therefore, it doesn't require additional grounnding or bonding.


Thats why i quoted 250.90 for a coverall whether or not its being used as an EGC. It would still be required to be bonded to.

Rick
 

RUWired

Senior Member
Location
Pa.
Would 392.7 not cover that ?

392.7 Grounding.
(A) Metallic Cable Trays. Metallic cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250.


IMO 250.96 is debatable and part-4 would apply to raceways. Cable trays are more of a support system and would not be covered under part-4.

Rick
 

Smart $

Esteemed Member
Location
Ohio
IMO 250.96 is debatable and part-4 would apply to raceways. Cable trays are more of a support system and would not be covered under part-4.

Rick
See highlighting....
392.7 Grounding.
(A) Metallic Cable Trays. Metallic cable trays that support
electrical conductors shall be grounded as required for
conductor enclosures in accordance with 250.96 and Part
IV of Article 250.


250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor,
cable sheath, enclosures, frames, fittings, and other metal
non?current-carrying parts that are to serve as grounding
conductors, 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. Any nonconductive paint, enamel, or similar coating
shall be removed at threads, contact points, and contact
surfaces or be connected by means of fittings designed so
as to make such removal unnecessary.


250.86 Other Conductor Enclosures and Raceways. Except
as permitted by 250.112(I), metal enclosures and raceways
for other than service conductors shall be connected
to the equipment grounding conductor.
As for 250.86, if you don't bond the tray to the equipment, your tray will not be connected to the EGC... though on this one, I see it overlooked on occasion.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
It is my opinion, and several others, bonding is not required from cable tray to utilization equipment when using type TC-ER cable even in hazardous locations. ...
It would be my opinion that 501.30(A) and 502.30(A) require bonding of the cable tray to the equipment and to the supply grounding system.
 

tryinghard

Senior Member
Location
California
It is my opinion, and several others, bonding is not required from cable tray to utilization equipment when using type TC-ER cable even in hazardous locations. The cable tray system is strictly a support system and is not being used as an equipment grounding conductor. If there is an NEC section that states a bonding jumper is required, I would appreciate you letting me know where that is. Thanks.

If a short occurs to the tray will the specific OCPD operate? In my opinion 392.7, 250.96, & 250.4(A)(3)-(5) make this very clear that the tray requires bonding for effective ground fault path.
 
It is my opinion, and several others, bonding is not required from cable tray to utilization equipment when using type TC-ER cable even in hazardous locations. The cable tray system is strictly a support system and is not being used as an equipment grounding conductor. If there is an NEC section that states a bonding jumper is required, I would appreciate you letting me know where that is. Thanks.

In my view it is the engineers, designers and installers responsibility to determine IF the NEC provides sufficient protection. If they determine that the ungrounded tray COULD become energized, it is their responsibility to take appropriate measures regardless if according to their interpretation the NEC would NOT require such measures.

The NEC is minimum requirement and is being revised every 3 years. In some cases the revision corrects oversights, or clarifies language so the intent is clear.
 

dicklaxt

Senior Member
I have designed many miles of tray systems over the years,,,,,,,,,the parameters all engr companies I have worked for were very similar. All cable trays will be electrically continuous ,,,,,,,,,,,starting at the gear the tray is either terminated at the gear or bonded to the gear,all cable trays are bonded together side to side and vertically when more than one level every 80 to 100 feet,the tray system is tied to the plant ground system(grid) at 80 to 100 foot intervals on each side of the racks providing two paths to ground at these junctures.The drops from tray to motor were done with rigid conduit that was secured on the tray rail with an approved fitting maintaining ground continuity.All loose fitting boltups ie: expansion joints, hinges etc will have bonding jumpers across the joint.The trays system must be electrically continious not the trays themselves,in other words the power cables can jump across a gap from tray to tray as long as the trays were bonded together.These trays were bonded together for ground fault and safety.The gounded conductor routed with the feeders would be used for clearing the circuit.

The gounding in and around substations,control rooms as well as Lightning Protection is another breed of cats.

dick
 
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