Service Neutral
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Ed MacLaren
Senior Member
Re: Service Neutral
Why would the (Multiple Grounded) Neutral have to be "disconnected" in the particular system under discussion, and not in others?
The neutral conductor, in virtually every single phase three-wire and three phase four-wire service in North America, is not switched or overcurrent protected.
In my house, my workplace, and in most building services that I have seen, the multiple grounded utility neutral extends un-switched, and un-fused, all the way to the load devices.
Why do we not hear more about the problem you describe?
Ed
Bennie, I have asked this question before, but have never recieved an answer. I will try again.
Why would the (Multiple Grounded) Neutral have to be "disconnected" in the particular system under discussion, and not in others?
The neutral conductor, in virtually every single phase three-wire and three phase four-wire service in North America, is not switched or overcurrent protected.
In my house, my workplace, and in most building services that I have seen, the multiple grounded utility neutral extends un-switched, and un-fused, all the way to the load devices.
Why do we not hear more about the problem you describe?
Ed
Ed MacLaren
Senior Member
Re: Service Neutral
How would they perform their intended function of clearing line-to-enclosure faults by providing a low impedance current path, if they weren't connected to "anything that will constitute a complete circuit"?
Ed
[ March 13, 2004, 12:03 PM: Message edited by: Ed MacLaren ]
You made this statement with regard to equipment bonding (grounding) conductors.
How would they perform their intended function of clearing line-to-enclosure faults by providing a low impedance current path, if they weren't connected to "anything that will constitute a complete circuit"?
Ed
[ March 13, 2004, 12:03 PM: Message edited by: Ed MacLaren ]
Re: Service Neutral
Most of these incidents are wrote off as equipment breakdown on the premises. Some are called "Acts of God" from lightning strikes. Equipment may be rated for fault current when fault is on the premises, but the equipment will not withstand a high to low fault.
Most winding to winding faults are contained by the MGN connection at the distribution transformer.
Utilities will not discuss this phenomenon due to litigation.
The reason the neutral should be disconnected from the premises system is more important when the back up system is for emergency purposes. A utility fault can destroy the emergency system.
When no emergency exists, the neutral disconnecting is not as important.
Disconnecting the neutral is an extra precaution for maintaining critical power continuity.
Most of these incidents are wrote off as equipment breakdown on the premises. Some are called "Acts of God" from lightning strikes. Equipment may be rated for fault current when fault is on the premises, but the equipment will not withstand a high to low fault.
Most winding to winding faults are contained by the MGN connection at the distribution transformer.
Utilities will not discuss this phenomenon due to litigation.
The reason the neutral should be disconnected from the premises system is more important when the back up system is for emergency purposes. A utility fault can destroy the emergency system.
When no emergency exists, the neutral disconnecting is not as important.
Disconnecting the neutral is an extra precaution for maintaining critical power continuity.
- Location
- Illinois
- Occupation
- retired electrician
Re: Service Neutral
Bennie,
If the service has a grounded conductor, there is no code compliant way to isolate the two systems. The EGCs of each system are requried to be connected to any common enclosure like a transformer case or a transfer switch.
Don
Bennie,
If the service has a grounded conductor, there is no code compliant way to isolate the two systems. The EGCs of each system are requried to be connected to any common enclosure like a transformer case or a transfer switch.
Don
Re: Service Neutral
For a premises wiring system to be separate from the utility system, the transfer switch must be the service switch. It will switch between the utility system and the local generator system.
A generator, after the service switch, can never be a separate system, anymore than a transformer.
A separately derived system is the entire premises wiring system, not just parts of the system.
I will drop this topic, it goes no where. The code panel does not research the true meaning of a separately derived system, instead, they change the definition to match their perception.
Instead of playing the game according to the rules, they change the rules to match their game.
For a premises wiring system to be separate from the utility system, the transfer switch must be the service switch. It will switch between the utility system and the local generator system.
A generator, after the service switch, can never be a separate system, anymore than a transformer.
A separately derived system is the entire premises wiring system, not just parts of the system.
I will drop this topic, it goes no where. The code panel does not research the true meaning of a separately derived system, instead, they change the definition to match their perception.
Instead of playing the game according to the rules, they change the rules to match their game.
Ed MacLaren
Senior Member
Re: Service Neutral
In our local hospital, the generators pick up approximately 1/3 of the total load. The critical loads are supplied from a separate switchgear, and they must be operated from the generators for 30 minutes each week.
Ed
As Bob pointed out earlier in this thread, stand-by generators rarely pick up the total building load.
In our local hospital, the generators pick up approximately 1/3 of the total load. The critical loads are supplied from a separate switchgear, and they must be operated from the generators for 30 minutes each week.
Ed
- Location
- Massachusetts
Re: Service Neutral
Bennie all of that is your opinion and that is great.
It is not the opinion of the NFPA, the NEC is their code book and they can make the rules as they see fit.
I read your posts and try to understand the point you are so set in making.
What is the 'real' problem you see, not just the definition discrepancy you see, but the safety problem?
I do not have the years in that you do, but I see what we do as working great, the company I work for installs 100s of NEC defined SDS each year, I do not see any of these having problems.
What am I missing?
Bennie all of that is your opinion and that is great.
It is not the opinion of the NFPA, the NEC is their code book and they can make the rules as they see fit.
I read your posts and try to understand the point you are so set in making.
What is the 'real' problem you see, not just the definition discrepancy you see, but the safety problem?
I do not have the years in that you do, but I see what we do as working great, the company I work for installs 100s of NEC defined SDS each year, I do not see any of these having problems.
What am I missing?
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Service Neutral
Bennie,
You said;
As to your challenge: Your turn.
Bennie,
You said;
The statements that have been supplied here, for the most part, ARE proven methods of safe electrical installation practices and ARE documented in the NEC.
As to your challenge: Your turn.
- Location
- Massachusetts
Re: Service Neutral
[ March 13, 2004, 08:26 PM: Message edited by: iwire ]
Bennie what part of my post suggests I do not want to discuss Service Neutrals?
[ March 13, 2004, 08:26 PM: Message edited by: iwire ]
Re: Service Neutral
My point is; To understand the details of proper equipement grounding, the equipment has to have a proper technical term.
A major part of grounding revolves around the definition of a separately derived system. I go by the NEC definition, not the contrived definition in the handbook and Soares grounding book.
My point is; To understand the details of proper equipement grounding, the equipment has to have a proper technical term.
A major part of grounding revolves around the definition of a separately derived system. I go by the NEC definition, not the contrived definition in the handbook and Soares grounding book.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Service Neutral
Bennie,
I love the way you ignor the specific questions that are asked about your theories!
Let's see if this is something that you can ignor!
Bennie,
I love the way you ignor the specific questions that are asked about your theories!
Let's see if this is something that you can ignor!
Is this more to your liking?
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Service Neutral
Huh?
The other one and this one from the 2002 NEC are different.
Huh?
The other one and this one from the 2002 NEC are different.
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Service Neutral
Since the second one is from the 2002 NEC, I thought you would like the first definition I posted?
Since the second one is from the 2002 NEC, I thought you would like the first definition I posted?
Re: Service Neutral
I like the NEC definition. If this definition were rewritten, I would write;
AC premises wiring system with no direct external connection.
This will eliminate a transformer, and include a generator if supplying entire premises wiring load, as a separately derived system.
I like the NEC definition. If this definition were rewritten, I would write;
AC premises wiring system with no direct external connection.
This will eliminate a transformer, and include a generator if supplying entire premises wiring load, as a separately derived system.
- Location
- Massachusetts
Re: Service Neutral
Why?
Why?
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