More than one place to derive a ground?

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jbmdux

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Location
Rhode Island
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Principal Project Engineer
I have a new house with a single phase service. I have an automatic transfer switch for my generator. The 200 amp breaker at the auto transfer switch is used as an emergency disconnect and a service disconnect.

There are 2 legs and a neutral from the meter trough that are brought into the auto transfer switch which has an integral 200 amp breaker on the normal supply. The generator connection has 4 conductors, L1 and L2 connected to the transfer switch, a neutral connected to the neutral bus in the ATS and a ground connected to a ground bus in the ATS (this ground is only a chassis ground for the generator). The neutral bus and ground bus are bonded here.

There are only 3 conductors from the ATS cabinet to the breaker panel in the house (about 140 feet away), L1, L2 and a neutral. There is no ground conductor.

There is no main breaker at the panel. At the panel there is a ground conductor run outside to 2 ground rods and the neutral bus is bonded to the ground bus in the panel via a bonding screw.

Questions:
What is the better method of connection, what I have or consider the ATS to be service entrance and have the ground derived there (add ground rod(s)) and consider the panel in the house a sub panel?
In that arrangement, I know I need a ground conductor (minimum #6) run to the panel with the high sides and the neutral and then separate the neutral and the ground in the panel.
If this is better, is it best to abandon the existing ground rods. I don't think I want to be the best ground in the neighborhood.

I will be adding a tap off the existing line (10 foot rule) for a shed. While scoping that out I realized there was no ground from the cabinet where the main breaker is to the breaker panel. This got me wondering.
 
jbmdux said:
There are only 3 conductors from the ATS cabinet to the breaker panel in the house (about 140 feet away), L1, L2 and a neutral. There is no ground conductor.
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Are these in the same structure? What is the wiring method to the panel?
 
jbmdux said:
I have a new house with a single phase service. I have an automatic transfer switch for my generator. The 200 amp breaker at the auto transfer switch is used as an emergency disconnect and a service disconnect.

There are 2 legs and a neutral from the meter trough that are brought into the auto transfer switch which has an integral 200 amp breaker on the normal supply. The generator connection has 4 conductors, L1 and L2 connected to the transfer switch, a neutral connected to the neutral bus in the ATS and a ground connected to a ground bus in the ATS (this ground is only a chassis ground for the generator). The neutral bus and ground bus are bonded here.

There are only 3 conductors from the ATS cabinet to the breaker panel in the house (about 140 feet away), L1, L2 and a neutral. There is no ground conductor.

There is no main breaker at the panel. At the panel there is a ground conductor run outside to 2 ground rods and the neutral bus is bonded to the ground bus in the panel via a bonding screw.
Click to expand...
If there are not more than 6 mains it may be compliant with older verions of the NEC. Presuming these are two different structures 140 feet apart,
jbmdux said:
Questions:
What is the better method of connection, what I have or consider the ATS to be service entrance and have the ground derived there (add ground rod(s)) and consider the panel in the house a sub panel?
Click to expand...
The ATS is your service disconnect, what you have is a non-compliant new feeder or a existing feeder that complied with a older version of the code.
jbmdux said:
In that arrangement, I know I need a ground conductor (minimum #6) run to the panel with the high sides and the neutral and then separate the neutral and the ground in the panel.
If this is better, is it best to abandon the existing ground rods.
Click to expand...
Each building or structure needs a Grounding Electrode System (GES), if its a old 3-wire feeder or a service you attach it to the neutral in the first disconnect.
jbmdux said:
I will be adding a tap off the existing line (10 foot rule) for a shed. While scoping that out I realized there was no ground from the cabinet where the main breaker is to the breaker panel. This got me wondering.
Click to expand...
The neutral was allowed to serve as both a ground and a neutral in older codes provided that there was not a parallel metallic path like a water or CATV line for example.
 
It sounds to me like the 200A breaker in the ATS is the service disconnect. The grounding electrode conductor to the ground rods should be run from the ATS, not from the downstream subpanel. Possibly the GEC could be terminated upstream of the ATS but with a generator I think it's better at the ATS.

A separate, more serious issue is that an EGC needs to be run from the ATS to the panel.
 
jbmdux said:
the ATS is on a pedestal with the meter about 140 feet from the house.
Click to expand...
Then keep the grounding at the house, and the ATS should be grounded too if isn't already.

The 3-wire feeder you describe might have been code compliant if installed before the 2005 code was in effect. (I think that's the year, iirc.) However nowadays a separate ground wire is required between the ATS and the house. I think infinity is asking about the wiring method in the hope you have a raceway that an EGC can be pulled through.
 
jaggedben said:
Then keep the grounding at the house, and the ATS should be grounded too if isn't already.

The 3-wire feeder you describe might have been code compliant if installed before the 2005 code was in effect. (I think that's the year, iirc.) However nowadays a separate ground wire is required between the ATS and the house. I think infinity is asking about the wiring method in the hope you have a raceway that an EGC can be pulled through.
Click to expand...
This is in Rhode Island and we are still on the 2020 code.
I answered infinity. It is in conduit.
 
If there no metallic paths between structures I would not recommend pulling in a EGC, unless there's like pool in-between, its no different than the Multi Grounded Neutral MGN utility system.
At the same structure I would end the MGN system at the first disconnect whatever you choose to call it.
 
WD40 said:
If there no metallic paths between structures I would not recommend pulling in a EGC, unless there's like pool in-between, its no different than the Multi Grounded Neutral MGN utility system.
At the same structure I would end the MGN system at the first disconnect whatever you choose to call it.
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I am aligned. I wish I could have included the SLD. If I had you would see there is only one disconnect and that is the 200 amp breaker that is part of the ATS. Look up the generac ATS schematic. I will find and post a link when at my computer.
 
jbmdux said:
I have a new house with a single phase service. I have an automatic transfer switch for my generator. The 200 amp breaker at the auto transfer switch is used as an emergency disconnect and a service disconnect.
Click to expand...
Are you doing the work yourself, or do you have an electrician?
 
Then I'm sorry, but we aren't allowed per Forum rules to help with your project unless you are an electrician, or this is part of your job. We have had to deny other engineers on DIY so we try to be consistent.
Hope you understand!
 
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