In the 2005 NEC page 70-96 250.24(A)(3)....I look in the definition section on what the code means of the phrase "dual fed service" ...what I have here is a back up generator and service feeder from my local utility would these be considered as dual feed to my system....??? if not then I pose this question ....this back up generator the neutrals are not part of the transfer switch so it is not a separately derived system....my question is at the service I have a cold water and ufer ground and at the generator I have a ground rod and ufer ground can i connect these grounds to common point??? like my equipment ground at the generator .If so where is this in the 2005 code...... thank you
Definition of "Dual Fed Service"
- Thread starter msilva
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Re: Definition of "Dual Fed Service"
Since the neutrals are not switched at the transfer switch (I think that means you have a 3 pole transfer switch), yes you should connect the grounding systems together. The neutral-ground bonding should be at the utility service. Any neutral to ground bonds in the generator should be removed.
A dual-fed service would be two separate sets of service entrance conductors.
Steve
Since the neutrals are not switched at the transfer switch (I think that means you have a 3 pole transfer switch), yes you should connect the grounding systems together. The neutral-ground bonding should be at the utility service. Any neutral to ground bonds in the generator should be removed.
A dual-fed service would be two separate sets of service entrance conductors.
Steve
Re: Definition of "Dual Fed Service"
A dual fed service is one that is set up for CLOSED SEQUENCE transfer from one power source to another. This involves paralleling the 2 power sources while transferring from one source to another.
An example is a switchboard that is designed to be fed by 1 or 2 transformers depending on load growth. If you only have high load for a few months a year you can save on the no load losses of the second transformer by deenergizing it.
Another example is a switchboard that is fed by 2 services for reliability purposes and there is a way to temporarily parallel the 2 services when switching from 1 to another.
A third example is a switchboard that parallels a service and a generator, what is known as cogeneration. This is one of the oldest uses because back before World War 2 most large users had to contribute generation to the grid. In fact, some urban utilities such as Ohio Edison's predecessor originally had no generation of their own and bought all of their power from the factories.
A dual fed service is one that is set up for CLOSED SEQUENCE transfer from one power source to another. This involves paralleling the 2 power sources while transferring from one source to another.
An example is a switchboard that is designed to be fed by 1 or 2 transformers depending on load growth. If you only have high load for a few months a year you can save on the no load losses of the second transformer by deenergizing it.
Another example is a switchboard that is fed by 2 services for reliability purposes and there is a way to temporarily parallel the 2 services when switching from 1 to another.
A third example is a switchboard that parallels a service and a generator, what is known as cogeneration. This is one of the oldest uses because back before World War 2 most large users had to contribute generation to the grid. In fact, some urban utilities such as Ohio Edison's predecessor originally had no generation of their own and bought all of their power from the factories.
john m. caloggero
Senior Member
Re: Definition of "Dual Fed Service"
Your installation is considered a separately derived system. You haven't provided sufficient information to be provided with specifics, however, my concern is that if the neutral at the generator is grounded to a metal water pipe that is the same as the one that the service is grounded to, then the water pipe and any metallic raceways will be in parallel with the neutral conductor, thereby allowing neutral current to flow on the piping and conduit.
Your installation is considered a separately derived system. You haven't provided sufficient information to be provided with specifics, however, my concern is that if the neutral at the generator is grounded to a metal water pipe that is the same as the one that the service is grounded to, then the water pipe and any metallic raceways will be in parallel with the neutral conductor, thereby allowing neutral current to flow on the piping and conduit.
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