Grounding Bushing.

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overamped

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Location
California
I'm installing a 800 amp 480 volt panel and it's being fed by three parallel runs of 250 MCM with a 1/0 ground in each of the three conduits. Do I need to use grounding bushings on the three conduits inside the breaker panel I am feeding? If so what table do I use to size it and does each conduit get it's own bonding wire?
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
I'm installing a 800 amp 480 volt panel and it's being fed by three parallel runs of 250 MCM with a 1/0 ground in each of the three conduits. Do I need to use grounding bushings on the three conduits inside the breaker panel I am feeding? If so what table do I use to size it and does each conduit get it's own bonding wire?

Check article 250 under bonding.... circuits over 250V :)
 

overamped

Member
Location
California
Check article 250 under bonding.... circuits over 250V :)

So do I need a bonding wire only if I use a concentric knock-out or is it considered a supply side bonding jumper and I either use one wire and size it based on 250-122 or three wires and size it based on 250-66.

Thank you for your reply by the way.
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
So do I need a bonding wire only if I use a concentric knock-out or is it considered a supply side bonding jumper and I either use one wire and size it based on 250-122 or three wires and size it based on 250-66.

Thank you for your reply by the way.

The bonding wire and the supply side Bonding jumper are two different animals...
 

ActionDave

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Location
Durango, CO, 10 h 20 min from the winged horses.
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Licensed Electrician
I'm installing a 800 amp 480 volt panel and it's being fed by three parallel runs of 250 MCM with a 1/0 ground in each of the three conduits. Do I need to use grounding bushings on the three conduits inside the breaker panel I am feeding? If so what table do I use to size it and does each conduit get it's own bonding wire?

So do I need a bonding wire only if I use a concentric knock-out or is it considered a supply side bonding jumper and I either use one wire and size it based on 250-122 or three wires and size it based on 250-66.....
Confusing stuff here. SSBJ is for services. Since you said 1/0 ground I'll guess it's an EGC and a feeder.

Quick and dirty rule for bonding jumpers is 250.66 for the Service or SDS and 250.122 for Feeders.
 

augie47

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Staff member
Location
Tennessee
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State Electrical Inspector (Retired)
Confusing stuff here. SSBJ is for services. Since you said 1/0 ground I'll guess it's an EGC and a feeder.

Quick and dirty rule for bonding jumpers is 250.66 for the Service or SDS and 250.122 for Feeders.

adding one step, and again assuming "ground" in this case means equipment grounding conductor on a feeder ( as opposed to serice grounded conductor),
250.97 will help clarify if a bonding jumper is needed. Unless you encounter concentric/eccentric one is normally not needed.
 

jtinge

Senior Member
Location
Hampton, VA
Occupation
Sr. Elec. Engr
Confusing stuff here. SSBJ is for services. Since you said 1/0 ground I'll guess it's an EGC and a feeder.

Quick and dirty rule for bonding jumpers is 250.66 for the Service or SDS and 250.122 for Feeders.


250.102 should be used for sizing grounded conductors and "bonding" jumpers. Supply side bonding jumpers can be used on services and SDS's. 250.66 is for sizing grounding electrode conductors.
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I'm installing a 800 amp 480 volt panel and it's being fed by three parallel runs of 250 MCM with a 1/0 ground in each of the three conduits. Do I need to use grounding bushings on the three conduits inside the breaker panel I am feeding? If so what table do I use to size it and does each conduit get it's own bonding wire?

If you use a metallic conduit then you do not need an EGC within each parallel raceway. If you choose to use a wire type EGC then it's sized according to 250.122 and 800 amps, which as you've stated is #1/0. If no concentric or eccentric KO's are encountered then bonding jumpers are not required even at 480 volts. If required they would be #1/0 also.
 
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