Two switchboards

[Wire-Smith]

I think utility around here do give another transformer if for fire pump and thats my case.

So what if you have two separate utiltiy transformers? Would this still happen?

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Yes, because utility secondary is likely grounded to the multipoint grounded utility neutral and then you are likely going to bond again at premises.
Not a concern to me if main bonds are physically close with a good local bond between them, or you use a premises isolation transformer on any of the services with neutral loads, before any neutral load on the system. And bond that isolation transformer secondary only at the transformer.

 

[Wire-Smith]

Yes, because utility secondary is likely grounded to the multipoint grounded utility neutral and then you are likely going to bond again at premises.
Not a concern to me if main bonds are physically close with a good local bond between them, or you use a premises isolation transformer on any of the services with neutral loads, before any neutral load on the system. And bond that isolation transformer secondary only at the transformer.

Edit
Change last sentence to " only at one location."

 

[hhsting]

Edit
Change last sentence to " only at one location."

Ok what about I have something like the attached sketch? Top is exterior view bottom is actual wiring of two service disconnects. It has local bond and swbd as close as possible.

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[Wire-Smith]

Ok what about I have something like the attached sketch? Top is exterior view bottom is actual wiring of two service disconnects. It has local bond and swbd as close as possible.

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Looks good to me, I obviously don't know how far apart the panels are or what non current carrying metal equipment is in between them, but if they are close there would likely be no problems and therefore arguably no code violation

 

[Wire-Smith]

About GEC though, I should add SWB2 GEC should be as short as practical to the actual grounding electrode system

 

[electrofelon]

Wire-Smith,

In my opinion, you are overly concerned about the (potential) objectionable current issue. We have buildings with separate services (or sets of SEC feeding non grouped disconnects) all the time. What current is objectionable is non rigorously defined and no one really seems to worry about it too much as it is usually unavoidable. Actually, I would think the further apart the disconnects are the better.

Regarding the bonding, I think how it is done depends on if 250.64(D) applies to disconnects for separate services, which IMO isnt really clear. If it does, you answer is one of the options in (D). IF not , just treat them separately, keeping in mind 250.50.

 

[Wire-Smith]

Wire-Smith,

In my opinion, you are overly concerned about the (potential) objectionable current issue. We have buildings with separate services (or sets of SEC feeding non grouped disconnects) all the time. What current is objectionable is non rigorously defined and no one really seems to worry about it too much as it is usually unavoidable. Actually, I would think the further apart the disconnects are the better.

Regarding the bonding, I think how it is done depends on if 250.64(D) applies to disconnects for separate services, which IMO isnt really clear. If it does, you answer is one of the options in (D). IF not , just treat them separately, keeping in mind 250.50.

i believe there will likely never be a problem. but my first hand experience of seeing sparking grounded non current carrying parts because of the installations you are describing and hearing stories of people getting shocked from those installations effects my view. although its not likely to be a problem, i believe we should design for everything to fail safe and operate safe and the installation you are describing does not clearly satisfy that. i believe i have presented options that contradict your statement of the current being unavoidable.

i believe its possible the OPs original design is compliant if there is little to no neutral current on the electrical system. otherwise i believe it is a clear violation of the NEC and rightfully so.

you say objectionable current is non rigorously defined, i disagree in a few ways. first off just because something is non rigorously defined does not mean the code section is invalid, i would argue you therefore must error on the side of caution, not overlook the section. second


ob·jec·tion·a·ble

[əbˈjekSH(ə)nəb(ə)l]

ADJECTIVE

• arousing distaste or opposition; unpleasant or offensive.

objectionable current is the best language i can think of for that section, it's any current you really don't want, you say non rigorously defined, i say subjective but also that the NEC is not for untrained people or to be used as a design manual, it is a minimum standard for safety. in some instances 20 amps on normally non-current carrying equipment is fine(and code compliant), in others 1 amp could be disastrous. i think people need to consider the possible problems, again the NEC is not a design manual or for the untrained, it's a minimum standard. and the NEC is for practical safeguarding and i don't see how requiring the main bonding connections to be physically close is impractical when you look from the practical view that a utility such as electricity is a privilege not a right or necessity more important than the risk of losing life to be able to use. grouping them together is not hard, it costs more, if you want electricity or want to make money off installing electrical equipment in most of the states you are supposed to install things if erroring, on the side of caution. you don't have the right to have an electrical system you have the privilege of having one that is beyond any reasonable argument, safe, and will not on its own harm someone. if there's no danger in circulating current in the OPs situation then i agree its compliant, but i do not take his omission of details on that subject as a determinant in that question. instead of investigating if it is safe i would take the easier route and error on side of caution for the minimal extra cost, keeping in mind its all for only having something as beneficial/desired but not absolutely needed like electricity that kills 440 people in u.s. by residential fires alone every year, causes nearly 34,000 u.s. residential fires alone every year, killed more than 300 and injured more than 4,000 on the job each year in the u.s. alone every year between 2003 and 2007.

Report highlights

Fires involving electrical failure or malfunction:

• 
  [*=left]Between 2010 and 2014, U.S. municipal fire departments responded to an average of 45,210 home structure fires involving electrical failure or malfunction. These fires caused annual averages of 420 civilian deaths, 1,370 civilian injuries, and $1.4 billion in direct property damage.
  [*=left]Non-home structure fires involving some type of electrical failure or malfunction accounted for an estimated annual average of 12 civilian deaths, 210 civilian injuries, and $614 million in direct property damage during this same period.

Fires involving electrical distribution or lighting equipment:

• 
  [*=left]U.S. fire departments responded to an estimated annual average of 31,960 non-confined home structure fires involving electrical distribution or lighting equipment in 2010-2014.
  [*=left]An estimated annual average of 14,760 non-confined and non-home fires involving electrical distribution and lighting equipment resulted in 20 civilian deaths, 190 civilian injuries, and $659 million in direct property damage each year

https://www.nfpa.org/News-and-Research/Data-research-and-tools/Electrical/Electrical



yeah, i'm concerned, but more of what i am trying to convey is in my opinion it is practical(when you consider what we are dealing with) to at least group them if you are going to have two bonds like that.



to your thought of them being at greater distances, my response is what i already said in this post that it is situation specific and my responses to the OP were of the mindset of "i wouldn't waste my time trying to figure out if there are absolutely no likely scenarios of this causing a problem, i would just group them(or the other options i presented". how would the enclosures being bolted and directly bonded together with their enclosures directly bonded to the main bonding connections pose a hazard? or are you considering them being just relatively close like say 10' apart, in that case i think if there is a big bonding jumper between them and no recognizable hazards for circulating current on the other metal in the area between them, like say a gas line or a jacuzzi, etc., i might think its okay but i would personally want them pretty much bolted together, being on opposite sides of a wall and a big bonding jumper between them would probably be okay i think depending on any other possible contributing factor or hazard. you saying "the further apart the better" makes me think you might actually recognize a possible hazard.


i will say i believe your view is more inline with what i would consider the more standard/prevalent view in the industry. but that doesn't change mine and i stand by what i have said. but am interested if you have anything else to add.

thanks​

its a privilege not a right, and very dangerous, i say we build with that in mind and if we are going to error, error on the side of caution. that's why i have posted what i have, not because i believe someone will likely die or the place will likely burn down, but because i think those things are plausible to happen and easily avoidable with the recommendations i provided.

 

[hhsting]

i believe there will likely never be a problem. but my first hand experience of seeing sparking grounded non current carrying parts because of the installations you are describing and hearing stories of people getting shocked from those installations effects my view. although its not likely to be a problem, i believe we should design for everything to fail safe and operate safe and the installation you are describing does not clearly satisfy that. i believe i have presented options that contradict your statement of the current being unavoidable.

i believe its possible the OPs original design is compliant if there is little to no neutral current on the electrical system. otherwise i believe it is a clear violation of the NEC and rightfully so.

you say objectionable current is non rigorously defined, i disagree in a few ways. first off just because something is non rigorously defined does not mean the code section is invalid, i would argue you therefore must error on the side of caution, not overlook the section. second


ob·jec·tion·a·ble

[əbˈjekSH(ə)nəb(ə)l]

ADJECTIVE

• arousing distaste or opposition; unpleasant or offensive.

objectionable current is the best language i can think of for that section, it's any current you really don't want, you say non rigorously defined, i say subjective but also that the NEC is not for untrained people or to be used as a design manual, it is a minimum standard for safety. in some instances 20 amps on normally non-current carrying equipment is fine(and code compliant), in others 1 amp could be disastrous. i think people need to consider the possible problems, again the NEC is not a design manual or for the untrained, it's a minimum standard. and the NEC is for practical safeguarding and i don't see how requiring the main bonding connections to be physically close is impractical when you look from the practical view that a utility such as electricity is a privilege not a right or necessity more important than the risk of losing life to be able to use. grouping them together is not hard, it costs more, if you want electricity or want to make money off installing electrical equipment in most of the states you are supposed to install things if erroring, on the side of caution. you don't have the right to have an electrical system you have the privilege of having one that is beyond any reasonable argument, safe, and will not on its own harm someone. if there's no danger in circulating current in the OPs situation then i agree its compliant, but i do not take his omission of details on that subject as a determinant in that question. instead of investigating if it is safe i would take the easier route and error on side of caution for the minimal extra cost, keeping in mind its all for only having something as beneficial/desired but not absolutely needed like electricity that kills 440 people in u.s. by residential fires alone every year, causes nearly 34,000 u.s. residential fires alone every year, killed more than 300 and injured more than 4,000 on the job each year in the u.s. alone every year between 2003 and 2007.

https://www.nfpa.org/News-and-Research/Data-research-and-tools/Electrical/Electrical



yeah, i'm concerned, but more of what i am trying to convey is in my opinion it is practical(when you consider what we are dealing with) to at least group them if you are going to have two bonds like that.



to your thought of them being at greater distances, my response is what i already said in this post that it is situation specific and my responses to the OP were of the mindset of "i wouldn't waste my time trying to figure out if there are absolutely no likely scenarios of this causing a problem, i would just group them(or the other options i presented". how would the enclosures being bolted and directly bonded together with their enclosures directly bonded to the main bonding connections pose a hazard? or are you considering them being just relatively close like say 10' apart, in that case i think if there is a big bonding jumper between them and no recognizable hazards for circulating current on the other metal in the area between them, like say a gas line or a jacuzzi, etc., i might think its okay but i would personally want them pretty much bolted together, being on opposite sides of a wall and a big bonding jumper between them would probably be okay i think depending on any other possible contributing factor or hazard. you saying "the further apart the better" makes me think you might actually recognize a possible hazard.


i will say i believe your view is more inline with what i would consider the more standard/prevalent view in the industry. but that doesn't change mine and i stand by what i have said. but am interested if you have anything else to add.

thanks​

its a privilege not a right, and very dangerous, i say we build with that in mind and if we are going to error, error on the side of caution. that's why i have posted what i have, not because i believe someone will likely die or the place will likely burn down, but because i think those things are plausible to happen and easily avoidable with the recommendations i provided.

Swbd #1 is for fire pump its fire pump ats controller breaker all in one. Yes that swbd will not have much neutral current balanced three phase motor load.
However swbd #2 will have neutral load its for bldg.

Are you allowed to have swbd #1for fire pump ats controller and bkr group 10 feet outside of swbd #2 exterior of bldg taken out of fire pump room?

Also vice versa are you allowed to group swbd #2 in fire pump room with swbd #1 230.2 exception would be one service fire pump is served by one service same as bldg?

Perhaps can get close as possible but group?

As far as gas pipes yes bldg would have gas pipe and if metal bond to GES.

 

[electrofelon]

i will say i believe your view is more inline with what i would consider the more standard/prevalent view in the industry. but that doesn't change mine and i stand by what i have said. but am interested if you have anything else to add.

Yes it definitely is, and in fact I sort of agree with you that the objectionable current issue is typically ignored or not enforced. For example consider a self contained meter socket that is bonded by the grounded conductor (and is not unbondable). Then put a service disconnect next two it with the two connected by a metal raceway. There will obviously be current flowing on the raceway. Pretty much anyone will call that "unavoidable" but IMO an inspector is within his rights to make you change the raceway to nonmetallic.

That said, I am not too worried about such objectionable current.

 

[lordofthisworld]

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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Is it just one service though? I thought code states you can’t have 2 services for exception for special conditions?

 

[Wire-Smith]

Yes it definitely is, and in fact I sort of agree with you that the objectionable current issue is typically ignored or not enforced. For example consider a self contained meter socket that is bonded by the grounded conductor (and is not unbondable). Then put a service disconnect next two it with the two connected by a metal raceway. There will obviously be current flowing on the raceway. Pretty much anyone will call that "unavoidable" but IMO an inspector is within his rights to make you change the raceway to nonmetallic.

That said, I am not too worried about such objectionable current.

i'm not trying to get into a pi***ng match, i hope you don't take this that way. i view a short conduit between a meter and a disconnect like in the scenario i believe you are describing as a very unlikely source of objectionable current. i say that because i see no harm that is plausible to come from that, i see it as a current path, but i see no danger. i think where our views part ways is the word objectionable, if it's not plausible to cause an issue it's not objectionable its just current in my opinion, if it is plausible to cause a problem then its objectionable current. what do you think?

thanks

 

[lordofthisworld]

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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IMHO, u would have to treat them as separate services, each would have it’s own GEC.

 

[electrofelon]

i'm not trying to get into a pi***ng match, i hope you don't take this that way. i view a short conduit between a meter and a disconnect like in the scenario i believe you are describing as a very unlikely source of objectionable current. i say that because i see no harm that is plausible to come from that, i see it as a current path, but i see no danger. i think where our views part ways is the word objectionable, if it's not plausible to cause an issue it's not objectionable its just current in my opinion, if it is plausible to cause a problem then its objectionable current. what do you think?

thanks

I am not really sure how objectionable current should be further defined honestly. A building with a single service and a metallic municipal water system will have current continuously flowing on a bare GEC (potentially running all the way thru the building) and/or building steel. That's a result of our (mostly) MGN distribution system and feeding multiple buildings from one transformer. I dont really like the idea of that, but it doesnt seem to be much of a problem. I guess I dont see the two services situation as being much different.

 

[Wire-Smith]

I am not really sure how objectionable current should be further defined honestly. A building with a single service and a metallic municipal water system will have current continuously flowing on a bare GEC (potentially running all the way thru the building) and/or building steel. That's a result of our (mostly) MGN distribution system and feeding multiple buildings from one transformer. I dont really like the idea of that, but it doesnt seem to be much of a problem. I guess I dont see the two services situation as being much different.

i completely agree with everything you said here. i think where our minds differ is " it doesn't seem to be much of a problem" i agree, but i don't think that means we shouldn't attempt to do something about it especially if its easy(i know subjective again) and just because its not on the news every night about fires or electrocutions caused by this, does not mean it doesn't happen, many accidents causes are not very well known, even if they sound like they are in the report. i think i must say again, no i do not think this is a problem to scream from the roof tops about, but in my opinion that doesn't mean it shouldn't be considered. i split atoms over everything, not in a painful or worried way, just naturally, don't take my long posts on this piddly issue as me thinking it is something major, there are much bigger issues in the industry. my desire for this conversation is as much for me to casually learn and think about my work with others as it is to try to point out a possible problem.


thanks

 

[electrofelon]

Is it just one service though? I thought code states you can’t have 2 services for exception for special conditions?

Whether a fire pump is on a second service or fed off the same service by an additional set of service entrance conductors is complicated and a bit sticky IMO. First, note that 230.40 doesnt seem to have an exception for it. Perhaps they intend it to fall under exception #2 but if so, it would have to be grouped since #2 says they have to be grouped and besides 230.72(A) exceptions doesnt cover 230.40 exception #2. It could fall under exception #1 or #4, but that only works for multi occupancy buildings.

So, I am not saying this is their intent, but the way I read it:
1. A fire pump fed from a 2nd service cant be grouped with the normal service (230.72(B))
2. IF it is fed off the same service, it has to be grouped in a single occupancy building or in a multiple occupancy building is allowed to not be grouped (230.72(A) exception)

:?:

 

[hhsting]

Nobody mentioned nec 250.58. Would not apply here?

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[Wire-Smith]

Nobody mentioned nec 250.58. Would not apply here?

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read the second paragraph of that

yes it applies


all grounding electrodes at a structure need bonded together, although i'm not sure what your getting at.

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used. Exception: Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete.

 

[hhsting]

250.58 Common Grounding Electrode not 250.50 Grounding Electrode System

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[hhsting]

Whether a fire pump is on a second service or fed off the same service by an additional set of service entrance conductors is complicated and a bit sticky IMO. First, note that 230.40 doesnt seem to have an exception for it. Perhaps they intend it to fall under exception #2 but if so, it would have to be grouped since #2 says they have to be grouped and besides 230.72(A) exceptions doesnt cover 230.40 exception #2. It could fall under exception #1 or #4, but that only works for multi occupancy buildings.

So, I am not saying this is their intent, but the way I read it:
1. A fire pump fed from a 2nd service cant be grouped with the normal service (230.72(B))
2. IF it is fed off the same service, it has to be grouped in a single occupancy building or in a multiple occupancy building is allowed to not be grouped (230.72(A) exception)

:?:

If you read closely nec 2017 handbook 230.72(b) commentary water pump is not same as fire pump of Article 695.



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[hhsting]

Looks good to me, I obviously don't know how far apart the panels are or what non current carrying metal equipment is in between them, but if they are close there would likely be no problems and therefore arguably no code violation

See attached sketch distance marked X is 22 feet. Its 22 feet from Swbd 1 to Swbd #2.

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