Neutral to Ground Connection

[blues]

I have a situation where I am installing a new genset.

The gen will be feed from an existing utility transformer to a new S.E. rated transfer switch & gen which will then feed an existing service panel. My question is if I make my N-G connection at the new CT cabinet do I need to disconnect the N-G at the main switchboard if it exist?

Thank You

 

[Strathead]

I have a situation where I am installing a new genset.

The gen will be feed from an existing utility transformer to a new S.E. rated transfer switch & gen which will then feed an existing service panel. My question is if I make my N-G connection at the new CT cabinet do I need to disconnect the N-G at the main switchboard if it exist?

Thank You

Much bigger issue than stated. For starters what is "G" is it a grounding electrode conductor, a bonding jumper to the metal cabinet, a grounding wire? Next, any bonding of the N-G needs to be done before or in the new S.E. rated transfer switch if the switch is, in fact the Service disconnecting means. And a generator will not "feed from an existing utility transformer." Sorry to be so picky but the wording is all important here.

 

[blues]

I understand what you are saying a gen is not feed from a xfmr. even though I stated it that way. Anyhow the N-G connection is made at the CT cabinet as shown per the attached PDF. My question remains does the N-G connection need to be remove from the existing MDP assuming one exist.

 

[Strathead]

I understand what you are saying a gen is not feed from a xfmr. even though I stated it that way. Anyhow the N-G connection is made at the CT cabinet as shown per the attached PDF. My question remains does the N-G connection need to be remove from the existing MDP assuming one exist.

Yes. As drawn the neutral and the ground bond will be removed at the panel and also at the transfer switch and the generator as long as the transfer switch is a 2 pole switch.

 

[publicgood]

Is this a 4-pole transfer switch? Is the generator intended to be separately derived? Does the generator feeder to the ATS contain a neutral?

 

[ActionDave]

Is this a 4-pole transfer switch? Is the generator intended to be separately derived? Does the generator feeder to the ATS contain a neutral?

The nature of the OPs question leads me to believe it is not an SDS.

 

[ActionDave]

I have a situation where I am installing a new genset.

The gen will be feed from an existing utility transformer to a new S.E. rated transfer switch & gen which will then feed an existing service panel. My question is if I make my N-G connection at the new CT cabinet do I need to disconnect the N-G at the main switchboard if it exist?

Thank You

Is there any chance you could put the transfer switch downstream of the existing service disconnect? That would save the effort of having to move the neutral/ground bond.

 

[publicgood]

The N-G happens at your first disconnecting means. Does the ATS have a breaker for the utility side?

 

[ActionDave]

The N-G happens at your first disconnecting means. Does the ATS have a breaker for the utility side?

It would have to to be a service rated transfer switch.

 

[kwired]

I have a situation where I am installing a new genset.

The gen will be feed from an existing utility transformer to a new S.E. rated transfer switch & gen which will then feed an existing service panel. My question is if I make my N-G connection at the new CT cabinet do I need to disconnect the N-G at the main switchboard if it exist?

Thank You

Bold part makes no sense. Perhaps you meant to say the "service" will be fed from an existing utility transformer?

CT cabinet is typically on supply side of service disconnecting means and shouldn't even really belong in the conversation of how to connect the generator.

If you have a service rated ATS, and it is installed as the service disconnecting means - it must have the grounded service conductor bonded and connected to the grounding electrode system - no bonding of the grounded conductor is allowed beyond this point - equipment grounding conductors must be run beyond this point.

Then comes whether or not your generator is a separately derived system or not. If not you don't bond the neutral in the generator and you run separate N and G to the generator. If is separately derived you must switch neutral with the transfer switch.

 

[publicgood]

If you have a service rated ATS, and it is installed as the service disconnecting means - it must have the grounded service conductor bonded and connected to the grounding electrode system

Yes

 

[kwired]

Originally Posted by kwired
If you have a service rated ATS, and it is installed as the service disconnecting means - it must have the grounded service conductor bonded and connected to the grounding electrode system

Yes

And if you are then supplying the existing service panel - it is no longer the service panel and you must separate neutrals and EGC's.

 

[ggunn]

Actually, it's pretty simple. Whichever way the transfer switch is thrown there shall be one and only one neutral to ground bond on the live circuitry supplying power to the loads.

 

[publicgood]

Actually, it's pretty simple. Whichever way the transfer switch is thrown there shall be one and only one neutral to ground bond on the live circuitry supplying power to the loads.

Not necessarily. As a 4-Pole switch, there may be N-G on each side if there is not a local disconnect at the generator.

 

[ActionDave]

Not necessarily. As a 4-Pole switch, there may be N-G on each side if there is not a local disconnect at the generator.

If wired correctly, be it a two, three, or four pole transfer switch, what ggun is saying is accurate.

 

[petersonra]

Not necessarily. As a 4-Pole switch, there may be N-G on each side if there is not a local disconnect at the generator.

the local disconnect has nothing to do with the N-G bond.

If the neutral is also switched, you could have a N-G bond on both line sides of the transfer switch but only one would be connected to the premises wiring system at a time since the transfer switch would also select the N-G bond to only the one that is switched on.

 

[petersonra]

I understand what you are saying a gen is not feed from a xfmr. even though I stated it that way. Anyhow the N-G connection is made at the CT cabinet as shown per the attached PDF. My question remains does the N-G connection need to be remove from the existing MDP assuming one exist.

This diagram is screwy.

It must be that one of the conduits on the top actually is fed from the meter and the other from the generator. If so the diagram shows the neutral and line conductors from the meter in separate conduits which I don't believe is allowed.

other than that, i think the diagram is Ok if the transfer switch is service rated and the generator does not have a N-G bond.

 

[ggunn]

the local disconnect has nothing to do with the N-G bond.

If the neutral is also switched, you could have a N-G bond on both line sides of the transfer switch but only one would be connected to the premises wiring system at a time since the transfer switch would also select the N-G bond to only the one that is switched on.

Bingo.