Grounding Conductor with HRG

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kevinjrr

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Here's the scenario.

2500KVA XFMR to 3000A main circuit breaker (MCB). Secondary voltage is 480VAC.
8-750MCM/PH on the secondary in conduit
High Resistance Grounding system employed and wired similar to Exhibit 250.21

Without the HRG (please verify), NEC 250.102(C)(2) indicates that the supply side bonding jumper should be:

#2/0 in each raceway OR
12.5% x 8 x 750MCM or a single 750MCM to bond the eight raceways per NEC Table 250.102(C)(1), note 1
Bonding cable routes from the xfmr XO to the main CB ground bus

With the HRG, there doesn't appear to be a need for a supply side bonding jumper as the XO will not be bonded to ground. Per Exhibit 250.21, it doesn't show a bonding conductor from the transformer to the MCB enclosure, but not certain if this illustration is considered "code".

Does the code require me to run a non-current carrying conductor from the xfmr to MCB?
 
Using an HIG system does not rescind the requirement to bond the transformer's non-current-carrying metal parts. An SSBJ is used to do that.

Also see 250.36(E). A conductor can be both the EBJ and SSBJ.
 
Smart $ said:
Using an HIG system does not rescind the requirement to bond the transformer's non-current-carrying metal parts. An SSBJ is used to do that.

Also see 250.36(E). A conductor can be both the EBJ and SSBJ.
Click to expand...

So, should we run a grounding conductor in each raceway (conduit) and bond to transformer case ground?
 
kevinjrr said:
So, should we run a grounding conductor in each raceway (conduit) and bond to transformer case ground?
Click to expand...
If not a service transformer, i.e. ahead of the service disconnecting means, yes.

If it is a service transformer, you could possibly get away with just running a single EBJ outside the conduits. See 250.36(G).
 
In general, other than the connection to earth, (solid, none or resistive) the grounding and bonding rules are the same no matter what type of earth connection is used.
 
Not trying to step on your toes, but let me restate that in a manner that I understand better...

"In general, the bonding and grounding electrode system rules are the same no matter the type of system grounding: solid, none, or resistive."
 
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Smart $ said:
Not trying to step on your toes, but let me restate that in a manner that I understand better...

"In general, the bonding and grounding electrode system rules are the same no matter the type of system grounding: solid, none, or resistive."
Click to expand...
I thought the general rule when writing about code stuff was to make it more confusing:)
 
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