Grounding of 600 amp 3 phase power

[AC.MIO]

Our building has a 3 phase 600 amp main breaker with three 200 amp panles feeding off the load side of the 600 amp main. In the three 200 amp panels they have three phases and a nuetral run to them. The 200 amp panels do not have a ground wire or a ground bar and the neutral bar is insulated from the panel.
Should I be treating these 200 amp panles as subpanels or as main panels were the ground and neutral bars are tyed together. If so should I throw a ground bar in the 200 amp panels and bond it to the panel and the neutral bar or do I need to run a ground wire back to the 600 amp main andbond it tho the neutral in the 600 amp main

Currently where the 600 amp main is the neutral and ground are tyed together( the ground goes from the main nutral bar, a groundding busing and to the water piper and nothing else. Thanks.

 

[augie47]

Anything on the load side of the 600 amp main is a "sub-panel" and there should be no neutral (grounded)-grounding connection. {250.24(A)(5)}
If they are connected to the main with a properly installed metallic conduit system that can serve as the required equipmemt grounding conductor.
(250.118)

 

[AC.MIO]

Thanks !

Thanks !

Thanks for the info and advice.

 

[kwired]

If you have metallic raceways they are your equipment grounding conductor to the sub panels and to the circuits feed out of them. If you do have any "wire" equipment grounding conductors they can not land on the neutral in the sub panels but can at the service equipment.

 

[maghazadeh]

kwired
If you have metallic raceways they are your equipment grounding conductor to the sub panels and to the circuits feed out of them. If you do have any "wire" equipment grounding conductors they can not land on the neutral in the sub panels but can at the service equipment.

Just adding to commends and recommendations others made here, you need to check and make sure that metallic raceways are not attached to panel/sub-panel enclosures, and main service enclosure through centrifugal knock-outs. If they do and there is no ground bushing bonding the raceways to the boxes, then you need to do so in order to have your raceways to be consider as equipment grounding conductors.

 

[augie47]

Just adding to commends and recommendations others made here, you need to check and make sure that metallic raceways are not attached to panel/sub-panel enclosures, and main service enclosure through centrifugal knock-outs. If they do and there is no ground bushing bonding the raceways to the boxes, then you need to do so in order to have your raceways to be consider as equipment grounding conductors.

Not necessarily... dependent on voltage (250.97) and other factors.

 

[maghazadeh]

Originally Posted by augie47
Not necessarily... dependent on voltage (250.97) and other factors.

augie47,
I don't have a code book nearby, could you tell me what (250.97) says.
Thank you

 

[ActionDave]

250.97 Bonding for Over 250 Volts
For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).

Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall be
permitted:

(1) Threadless couplings and connectors for cables with metal sheaths

(2) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets

(3) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets

(4) Listed fittings