I need some help. In 1999 code, service is defined as "from the serving utility." Service equipment is defined as connected to the service conductors. If an owner has 12kv service and their own outdoor 12KV to 480V transformer, then the building does not have service entrance equipment in it and article 250-24, for building services, does not apply, right! At least this is what a site engineer is telling me. If someone else has run into this,does NFPA define a priviate transformer as a private serving utility, or do you need to somehow use the definitions for a separately derived system. The site's transformer for this building sets 700' away and this guy does not want to bond the neutral to the building grounding electrode, which will definitely cause someone to draw a pretty good spark from the elevated neutral voltage.
NEC Service Definition
- Thread starter nvcape
- Start date
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websparky
Senior Member
- Location
- Cleveland, Ohio
Re: NEC Service Definition
Tell him "nice try!". Then tell him to read the entire sentence.
- Location
- Illinois
- Occupation
- retired electrician
Re: NEC Service Definition
The grounding at the building would be per 250.32(B)(1) or (B)(2). If an EGC is run with the feeder conductors to the building, the neutral is not permitted to be bonded to the building grounding electrode system. If an EGC is not run with the feeders, then the neutral must be bonded. I don't understand why the neutral voltage would be elevated at the building without the bond. The voltage to earth from the neutral at the building would be equal to the voltage drop on the neutral conductor between the transformer and the building.
Don
The grounding at the building would be per 250.32(B)(1) or (B)(2). If an EGC is run with the feeder conductors to the building, the neutral is not permitted to be bonded to the building grounding electrode system. If an EGC is not run with the feeders, then the neutral must be bonded. I don't understand why the neutral voltage would be elevated at the building without the bond. The voltage to earth from the neutral at the building would be equal to the voltage drop on the neutral conductor between the transformer and the building.
Don
- Location
- Illinois
- Occupation
- retired electrician
Re: NEC Service Definition
Dave,
In my opinion this is not a service, it is a feeder. Look at the definition of premises wiring system. The premises wiring starts at the service point.
Don
Dave,
In my opinion this is not a service, it is a feeder. Look at the definition of premises wiring system. The premises wiring starts at the service point.
Don
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: NEC Service Definition
Don,
You're right. I just couldn't resist!
Sounds like a crazy idea to me!
I would also look at 250-30. Grounding Separately Derived Alternating-Current Systems.
Don,
You're right. I just couldn't resist!
Sounds like a crazy idea to me!
I would also look at 250-30. Grounding Separately Derived Alternating-Current Systems.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: NEC Service Definition
Say...... This sounds kind of familiar.... doesn't it?
Say...... This sounds kind of familiar.... doesn't it?
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: NEC Service Definition
"Service equipment is defined as connected to the service conductors."
Not quite.
Not true.
"Service equipment is defined as connected to the service conductors."
Not quite.
"....then the building does not have service entrance equipment in it.... "
Not true.
Re: NEC Service Definition
Thanks so far, I think Dave is the closest. The service entrance conductors are 12kv and the service disconnect is at least 1 mile away, it's a huge site. Service equipment is defined as being connected to the load end of the service conductors to a building or structure for the main cut off of the supply. This is at 12 KV. The only thing I can find is that 230 states that "A building served shall be supplied by only one SERVICE unless otherwise permitted. Service conductors and equipment extend from the utility to the "wiring of the premises served". Premisises wiring is defined as interior and exterior wiring from the utility OR transformer. Maybe this is the code writer's out? I should be happy, if it's not a service, then I don't need to supply a service disconnect!
Thanks so far, I think Dave is the closest. The service entrance conductors are 12kv and the service disconnect is at least 1 mile away, it's a huge site. Service equipment is defined as being connected to the load end of the service conductors to a building or structure for the main cut off of the supply. This is at 12 KV. The only thing I can find is that 230 states that "A building served shall be supplied by only one SERVICE unless otherwise permitted. Service conductors and equipment extend from the utility to the "wiring of the premises served". Premisises wiring is defined as interior and exterior wiring from the utility OR transformer. Maybe this is the code writer's out? I should be happy, if it's not a service, then I don't need to supply a service disconnect!
- Location
- Illinois
- Occupation
- retired electrician
Re: NEC Service Definition
This is not a service and you do not need a service disconnect, but you do need a building disconenct per 225.31 through .33. This is very common type of installation in for industrial and campus type installations. 240.21(C)(4) was added to the code just for this type of installation. Under codes prior to the addition of this section, if the transformer was customer owned, the secondary conductors were required to have overcurrent protection at the transformer. The code change permitted customer owned distribution to follow almost the same rules as a utility service.
The only difference here is the bonding issue. If the feeder raceway is non-metallic and no EGC is provided this installation would be idential to a utility service. If an EGC is provided the required bonding of the neutral conductor is permitted only at a single location.
Don
This is not a service and you do not need a service disconnect, but you do need a building disconenct per 225.31 through .33. This is very common type of installation in for industrial and campus type installations. 240.21(C)(4) was added to the code just for this type of installation. Under codes prior to the addition of this section, if the transformer was customer owned, the secondary conductors were required to have overcurrent protection at the transformer. The code change permitted customer owned distribution to follow almost the same rules as a utility service.
The only difference here is the bonding issue. If the feeder raceway is non-metallic and no EGC is provided this installation would be idential to a utility service. If an EGC is provided the required bonding of the neutral conductor is permitted only at a single location.
Don
Re: NEC Service Definition
Thanks Don, the issue becomes that the serving transformer is about 700 feet away and the site only wants a ground at the transformer and not to bond the neutral to the ground electrode. Without this bond, the neutral in that distance becomes a problem. If the building does not have "service disconnect," then article 250 requirements for the second ground and some other things are out the window. Do you agree with the definition of "service," that it is the conductors and EQUIPMENT from the utility to the premises and that "premises wiring" connects to the service point? Would the service point then be the service equipment?
Thanks Don, the issue becomes that the serving transformer is about 700 feet away and the site only wants a ground at the transformer and not to bond the neutral to the ground electrode. Without this bond, the neutral in that distance becomes a problem. If the building does not have "service disconnect," then article 250 requirements for the second ground and some other things are out the window. Do you agree with the definition of "service," that it is the conductors and EQUIPMENT from the utility to the premises and that "premises wiring" connects to the service point? Would the service point then be the service equipment?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: NEC Service Definition
In Wisconsin the secondary of all customer owned substations (MV to LV) must be treated as service entrance equipment and installed as such.
In Wisconsin the secondary of all customer owned substations (MV to LV) must be treated as service entrance equipment and installed as such.
charlie
Senior Member
- Location
- Indianapolis
Re: NEC Service Definition
CMP-4 made an attempt to make Article 225 look like Article 230 as much as possible. If you look at the feeder going to a separate building, the feeder is "service like" and is installed similar to service conductors. Follow closely the rules in Article 225 and you will have an installation that looks and smells like a building service.
CMP-4 made an attempt to make Article 225 look like Article 230 as much as possible. If you look at the feeder going to a separate building, the feeder is "service like" and is installed similar to service conductors. Follow closely the rules in Article 225 and you will have an installation that looks and smells like a building service.
Re: NEC Service Definition
I just got educated and thought I would pass this along. When you bond the neutral to the grounding electrode, the neutral, if it should somehow open or become a higher resistance, will leave the building system at an elevated voltage. While this will not be noticed inside the bonded building, should someone get ahold of a hose bib outside the building and the earth or sidewalk is at a different potential, they get polked. My response to the instructor was that under normal operation, without the neutral bonded, I have seen an electrician get knocked off a ladder from an unexpected spark.
I just got educated and thought I would pass this along. When you bond the neutral to the grounding electrode, the neutral, if it should somehow open or become a higher resistance, will leave the building system at an elevated voltage. While this will not be noticed inside the bonded building, should someone get ahold of a hose bib outside the building and the earth or sidewalk is at a different potential, they get polked. My response to the instructor was that under normal operation, without the neutral bonded, I have seen an electrician get knocked off a ladder from an unexpected spark.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: NEC Service Definition
I'm curious as to why or how this is a problem?
- Location
- Illinois
- Occupation
- retired electrician
Re: NEC Service Definition
nvcape,
Don
nvcape,
Was this neutral grounded at any point?
Don
Re: NEC Service Definition
Normally, this would not even be a thought, but set the transformer 700' away, don't bond the neutral, run an equipment ground, have fairly high neutral current ( plus harmonics) for an office and the neutral will have a small voltage, V=IR. The handbook states that the neutral connection to a grounding electrode is to limit voltage to ground imposed by lightning, line surges and high voltage crossovers, also to stabilize the voltage to ground.
The explaination I got for not wanting to bond the neutral at any building is that this will cause the building ground to be at an elevated voltage, especially if the neutral path's resistance increased, say, as a result of a poor connection or cable problem. Then if someone, outdoors, touched a hose bib, they might feel a tingle. How much current would conduct through them back through earth to the transformer ground, I'm not sure. Anyway, it's another view.
Normally, this would not even be a thought, but set the transformer 700' away, don't bond the neutral, run an equipment ground, have fairly high neutral current ( plus harmonics) for an office and the neutral will have a small voltage, V=IR. The handbook states that the neutral connection to a grounding electrode is to limit voltage to ground imposed by lightning, line surges and high voltage crossovers, also to stabilize the voltage to ground.
The explaination I got for not wanting to bond the neutral at any building is that this will cause the building ground to be at an elevated voltage, especially if the neutral path's resistance increased, say, as a result of a poor connection or cable problem. Then if someone, outdoors, touched a hose bib, they might feel a tingle. How much current would conduct through them back through earth to the transformer ground, I'm not sure. Anyway, it's another view.
- Location
- Illinois
- Occupation
- retired electrician
Re: NEC Service Definition
nvcape,
Yes, if XO is bonded at the transformer and not at the building end of a 700' feeder there will be a small voltage between the grounded conductor and earth and you can create a spark. I doubt that this voltage would be any where near high enough for a normal person to even feel, let alone knock him off a ladder. He may have been startled by the spark and fell off of the ladder, but I don't think that it would have physically knocked him off.
Don
nvcape,
Yes, if XO is bonded at the transformer and not at the building end of a 700' feeder there will be a small voltage between the grounded conductor and earth and you can create a spark. I doubt that this voltage would be any where near high enough for a normal person to even feel, let alone knock him off a ladder. He may have been startled by the spark and fell off of the ladder, but I don't think that it would have physically knocked him off.
The same thing will happen under the same conditions with a service. Does the engineer also refuse to bond the neutral at a service disconnect?
Don
Re: NEC Service Definition
Your right. No one got hurt or zapped. When I do something that is not quite standard, I start thinking of expert witnesses and lawyers 10 years down the road (Hot Coffee!). There's usually someone that has already had experence and willing share in this forum. Thanks.
Your right. No one got hurt or zapped. When I do something that is not quite standard, I start thinking of expert witnesses and lawyers 10 years down the road (Hot Coffee!). There's usually someone that has already had experence and willing share in this forum. Thanks.
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