Two switchboards

[hhsting]

I have two service laterals from one utility transformer. One goes to swbd #1 and second goes to swbd #2.

In swbd #1 I have gnd bus and neutral bus, main bonding jumper, from neutral bar GECs to bldg steel, underground metal pipe, gnd rods.

Just so I can tie all building GE together, can I tie another GEC from swb#1 neutral bar and tie to Gnd bus of swbd #2 that has main bonding jumper? Code allows that? Or I need main bus bar outside with conductors going to GE and one conductor going to Swbd #1 and second conductor going to swbd #2?

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[petersonra]

I have two service laterals from one utility transformer. One goes to swbd #1 and second goes to swbd #2.

In swbd #1 I have gnd bus and neutral bus, main bonding jumper, from neutral bar GECs to bldg steel, underground metal pipe, gnd rods.

Just so I can tie all building GE together, can I tie another GEC from swb#1 neutral bar and tie to Gnd bus of swbd #2 that has main bonding jumper? Code allows that? Or I need main bus bar outside with conductors going to GE and one conductor going to Swbd #1 and second conductor going to swbd #2?

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IIRC, you can tie it to the first swbd ground bus if it is a ground bar that is at least 1" x 2".

 

[electrofelon]

Are these switchboards grouped? Are you sure they are service laterals off the transformer? Something doesn't seem right.

 

[hhsting]

Are these switchboards grouped? Are you sure they are service laterals off the transformer? Something doesn't seem right.

Its brand new building so I can see it. I have two sets of service conductors from one utility transformer: one goes to building swbd #1 and other swbd #2. Swbd #2 has building ats/controller fire pump load and breakers to other motor load related to fire pump so no both are not grouped in one location.

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[augie47]

The way I read 250.64(D), it is not allowed. A grounding electrode conductor must be brought from each service disconnect and terminated to the grounding electrodes or a common grounding electrode conductor sized for both disconnects or a bar as specified in 250.64(D)(1) and reference by petersonra above.
Removal of 1 switchboard can not interrupt the path of the other to the grounding electrode system.

 

[hhsting]

The way I read 250.64(D), it is not allowed. A grounding electrode conductor must be brought from each service disconnect and terminated to the grounding electrodes or a common grounding electrode conductor sized for both disconnects or a bar as specified in 250.64(D)(1) and reference by petersonra above.
Removal of 1 switchboard can not interrupt the path of the other to the grounding electrode system.

I dont think 250.64(D) applies. 250.64(D) which says if a building is supplied by a service with two or more disconnecting. So if you have one service with muiltiple service disconnect then 250.64(D) applies.

I have two services from one utility transformer.

 

[augie47]

As I read 230.2 what you have is considered one service.

 

[hhsting]

As I read 230.2 what you have is considered one service.

Ah 230.2 you mean when it says 1/0 AWG and larger running to same location and connected together at their supply end but not connected together at their load end considered one service.

 

[augie47]

Yes. and if you want to consider it as (2) services, to me, 250.64(F) would require the electrode conductor be run directly to the electrodes or the previously described "plate"

 

[hhsting]

Ah 230.2 you mean when it says 1/0 AWG and larger running to same location and connected together at their supply end but not connected together at their load end considered one service.

Yes. and if you wantt o consider it as (2) services, to me, 250.64(F) would require the electrode conductor be run directly to the electrodes or the previously described "plate"

Ok 230.2 says for the purpose of 230.40 exception no.2 only, ungrounded sets of conductors 1/0 awg and larger, running to the same location and connected at their supply end but not connected together at their load end shall be considered one service.

See for the purpose of 230.40 exception no. 2 in their.

Is that an extension of 230.40 exception no.2 i.e an addition to or is that implying if i have two to six disconnect grouped but not connected at load end but connected at supply end with 1/0awg or larger is one service? My swbd are not grouped.

 

[augie47]

Ok 230.2 says for the purpose of 230.40 exception no.2 only, ungrounded sets of conductors 1/0 awg and larger, running to the same location and connected at their supply end but not connected together at their load end shall be considered one service.

See for the purpose of 230.40 exception no. 2 in their.

Is that an extension of 230.40 exception no.2 i.e an addition to or is that implying if i have two to six disconnect grouped but not connected at load end but connected at supply end with 1/0awg or larger is one service? My swbd are not grouped.

OK, go back to post 9.. two services...

 

[hhsting]

Yes. and if you want to consider it as (2) services, to me, 250.64(F) would require the electrode conductor be run directly to the electrodes or the previously described "plate"

The plate in my case is the neutral bar in swbd #1. 250.64(F) does not say it cannot be the same busbar as in the switchboard so as long as the neutral busbar in swbd #1 is 0.25 in x 2 in wide and in accessible location. Switchboard neutral bus bar is accessible.

I dont see anywhere else in code above cannot be done. No?

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[augie47]

I find that to be a real "stretch" of the "common buss" wording but obviously we are of a different opinion.
You have mine in that is it's a violation.
Perhaps there will be more Forum input.

 

[david]

The plate in my case is the neutral bar in swbd #1. 250.64(F) does not say it cannot be the same busbar as in the switchboard so as long as the neutral busbar in swbd #1 is 0.25 in x 2 in wide and in accessible location. Switchboard neutral bus bar is accessible.

I dont see anywhere else in code above cannot be done. No?

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why don't you just go from 2nd service to building steel. And use building steel to bond any other electrodes that are part of the grounding electrode system. If these two laterals supplied two grouped service disconnects the NEC stipulates a tap to a common grounding electrode conductor.

If you do not do this for grouped disconnects why would you do this for two separate service disconnects

 

[hhsting]

why don't you just go from 2nd service to building steel. And use building steel to bond any other electrodes that are part of the grounding electrode system. If these two laterals supplied two grouped service disconnects the NEC stipulates a tap to a common grounding electrode conductor.

If you do not do this for grouped disconnects why would you do this for two separate service disconnects

If I had decision to make I would get busbar separate outside of swbd and have one GEC from swbd #1 , one GEC to swbd #2 to outside busbar and then have bonding jumpers from the busbar to GE.

But I am being questioned as to the installation of neutral bar as common bus in swbd #1 by the owners where is it in NEC code violation. Its accessible and bonding jumpers are going to GE and GEC come from swbd #2 to swbd #1 neutral bar. It complies per nec 250.64(F)(3) so as long as neutral bar in swbd #1 is 0.25 in by 2 in.

 

[david]

If I had decision to make I would get busbar separate outside of swbd and have one GEC from swbd #1 , one GEC to swbd #2 to outside busbar and then have bonding jumpers from the busbar to GE.

But I am being questioned as to the installation of neutral bar as common bus in swbd #1 by the owners where is it in NEC code violation. Its accessible and bonding jumpers are going to GE and GEC come from swbd #2 to swbd #1 neutral bar. It complies per nec 250.64(F)(3) so as long as neutral bar in swbd #1 is 0.25 in by 2 in.

Well from an authority prospective the plate is not an equipment ground or neutral bar in a panel nor a bar inside a dry transformer. I do not see the issue of providing a bonding plate/bar in the electric room provided for this purpose.

An authority at times needs to make this call

 

[hhsting]

Well from an authority prospective the plate is not an equipment ground or neutral bar in a panel nor a bar inside a dry transformer. I do not see the issue of providing a bonding plate/bar in the electric room provided for this purpose.

An authority at times needs to make this call

What providing bonding plate/bar in fire pump room instead of electric room?

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[david]

What providing bonding plate/bar in fire pump room instead of electric room?

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The assumption was #1 service was the larger service bonding jumpers from a plate at #1 location would be sized also correct for #2 service

 

[hhsting]

The assumption was #1 service was the larger service bonding jumpers from a plate at #1 location would be sized also correct for #2 service

I mean separate busbar out of service equipments per nec 250.64(f)(3) in accessible location in fire pump room location of swbd #2 instead of electric room.

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[Wire-Smith]

250.6 Objectionable Current. (A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non–current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current

two neutral to ground bonds on one electrical system(the same transformer)at two separated areas connected by conductive paths, i think this is your real problem.