confusion about sizing bonding jumper

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zyhml

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I am very pleasent to find this wonderful forum, by those old topics i learned so much knowledge. but there are still some question confued me. would you give me a hand? Your reply is very appreciated.
The question are : 1, how to size the bonding jumper of cable tray and conduit if i don't use it as EGC(i just bonding all cable tray section and those conduit connected to the cable tray, i'm confused if it is EGC when i bonding conduit to the cable tray), all equipments have their own EGC cable respectively) according to NEC code, may i use the minimum size 14AWG as bonding, if not, what could i take into account?
2, how to size the cable bonding the cable tray to grouding, i think it as EGC cable and choose the size according to table 250.102 by the maximum phase conductor in the cable tray, is it right?
3, if the HV panel and the transformer are in different location i means two different building in plant and i run the HV cable which belongs to clients to transformer room by cable tray, it means in the transformer room two different voltage level cable tray exist, shall i connect these two tray to the same gronding, if so, how to size the grounding cable to the HV cable tray.
4, if outdoor oil tank exists and i design a static-electrical discharge gronding system for it, the power panle feed by power cable with egc conductor is in this area, shall i connect the dedicated grounding system to the PE of panel?
 
zyhml said:
1 ...may i use the minimum size 14AWG as bonding, if not, what could i take into account?
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I would say no, you must size the bonding jumper for the cable tray according to the highest rated OCPD likely to energize the tray. So if you have a 30A circuit in the tray, a #10 EGC would be required.
250.96(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 effectively 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.
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2, how to size the cable bonding the cable tray to grouding, i think it as EGC cable and choose the size according to table 250.102 by the maximum phase conductor in the cable tray, is it right?
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I would agree.

I do not understand your questions 3 and 4, sorry, hope I helped somewhat.
 
thanks a lot!:)
1, 'serve as grounding conductors' in 250.96, i still confused what does it mean. is there situation where cable tray don't serve as grounding conductor?

3, question 3 is related to question 2, if we size bonding jumper according to 250.102, in situation i mentioned there are high voltage cable tray such as 10KV and 240V level cable tray in the same room, first do we need grounding the HV cable tray? second how to size the grounding cable?

4, i want to know do i need bonding the dedicated grounding system for oild tank and the power grounding from utility?

thanks again! :)
 
Is this aluminum ladder type tray?
You say it won't be used as the EGC so you just need bonding. Why aren't the splice plates bonding it?

Your bonding jumpers are sized from 250.102 and used only when you have mechanically discontinuous segments (usually limited to 6 feet). 392.6(A)

Trying to understand about the conduit. They have conduit clamps U.L. listed for bonding conduit to the tray. I usually see bonding bushings spec'd for rigid take-offs.
 
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