Have question about the grounded conductor in conduit or cable tray. Circuit is 4-500 kcmil per phase conductors and a grounded conductor feeding from a Substation switchboard to a MCC. Looking for the size and number of grounds required for installing in 4 conduits or installing in cable tray.
Ground conductor (not EGC) size for parallel conductors in conduit or cable tray
- Thread starter tedbayr
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
What size is required for the install? are you looking for the minimum size req.
kwired
Electron manager
- Location
- NE Nebraska
This is no different than sizing the grounded conductor for circuits without parallel conductors. The grounded conductor has to be able to carry any load imposed on it but can not be any smaller than the necessary equipment grounding conductor for the same circuit, or the grounding electrode conductor for service conductors, but can not be smaller than 1/0 AWG if it is part of a set of parallel conductors.
See 210.19(A)(1), 215.2(A)(2), 250.24, 310.10(H).
See 210.19(A)(1), 215.2(A)(2), 250.24, 310.10(H).
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
In my opinion, according to NEC Art.250.24(C)(2) Parallel Conductors in Two or More Raceways "the grounded conductor shall also be installed in parallel".
So, if there are 4 conduits each one has to be provided with a grounding conductor.
Art.310.10(H)(6) indicates for Equipment Bonding Jumpers art. 250.102 and here in(C) it is stated the size of the grounding conductor in each raceway "shall be based on the size of the ungrounded supply conductors in each raceway"
that means for 1*500 mcm will be 1/0 [copper].
If they run in the same cable tray[same raceway] a grounding conductor according to NEC Table 250.66 [for more than 1100 mcm copper has to be minimum 3/0].
However, art.250.24(C) Grounded Conductor Brought to Service Equipment.(1) Sizing for a Single Raceway. states: "in the same time not less than 12.5% of total mcm" [4*500=2000 mcm] it is 250 MCM.
So, if there are 4 conduits each one has to be provided with a grounding conductor.
Art.310.10(H)(6) indicates for Equipment Bonding Jumpers art. 250.102 and here in(C) it is stated the size of the grounding conductor in each raceway "shall be based on the size of the ungrounded supply conductors in each raceway"
that means for 1*500 mcm will be 1/0 [copper].
If they run in the same cable tray[same raceway] a grounding conductor according to NEC Table 250.66 [for more than 1100 mcm copper has to be minimum 3/0].
However, art.250.24(C) Grounded Conductor Brought to Service Equipment.(1) Sizing for a Single Raceway. states: "in the same time not less than 12.5% of total mcm" [4*500=2000 mcm] it is 250 MCM.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
So these are service entrance conductors?
Julius Right
Senior Member
- Occupation
- Electrical Engineer Power Station Physical Design Retired
In my opinion, as in o.p. is stated :"from Substation[utility, I guess]Switchboard:angel: to MCC[premises wiring?] then it could be "service" ,isn't it?:?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I doubt we will ever know as the op posted and never returned. I suspected it was a service for the reasons stated above.
- Status