Ground rods at separate building/garage/storage building.

[AGreen]

Are ground rods required at a separate building which is fed by a two pole breaker at a building near by? The new separate building is being fed by two ungrounded conductors, grounded conductor, and equipment grounding conductor. This goes into a small two space panel/disconnect. From there the two individual breakers feed lights and receptacles.

2020 NEC 250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuits(s)
Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non-current-carrying metal parts of equipment.

After reading this exception, my point of view says that a ground rod would not be required. Any input is appreciated!

Thank you

 

[tom baker]

Do you inspect electrical as part of your job or is this a personal project?
You do not have a multi wire branch circuit, you have a feeder to the new separate building.

 

[romex jockey]

Are ground rods required at a separate building which is fed by a two pole breaker at a building near by? The new separate building is being fed by two ungrounded conductors, grounded conductor, and equipment grounding conductor. This goes into a small two space panel/disconnect. From there the two individual breakers feed lights and receptacles.

2020 NEC 250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuits(s)
Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non-current-carrying metal parts of equipment.

After reading this exception, my point of view says that a ground rod would not be required. Any input is appreciated!

Thank you

pretty much GEC's follow OCPD's re> 250.32 (B)

~RJ~

 

[roger]

Feeder or Multi Wire Branch Circuit is the key and by the discription it appears to be a feeder and requires the GE's

Roger

 

[romex jockey]

Feeder or Multi Wire Branch Circuit is the key and by the discription it appears to be a feeder and requires the GE's

Roger

yes , but not always so Roger

old 250.32 B vs new 250.32 B

~RJ~

 

[infinity]

This goes into a small two space panel/disconnect. From there the two individual breakers feed lights and receptacles.

What size OCPD is at the other building? Sounds like you could make it a MWBC and a disconnecting means at the other end and not a feeder but with the two CB's at the other end it is a feeder by definition. Change the CB's to a multi-pole switch and you can avoid the GEC.

 

[Dennis Alwon]

yes , but not always so Roger

old 250.32 B vs new 250.32 B

~RJ~

A ground rod was required then also but the op mentioned 2020...

 

[Dennis Alwon]

Are ground rods required at a separate building which is fed by a two pole breaker at a building near by? The new separate building is being fed by two ungrounded conductors, grounded conductor, and equipment grounding conductor. This goes into a small two space panel/disconnect. From there the two individual breakers feed lights and receptacles.

2020 NEC 250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuits(s)
Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non-current-carrying metal parts of equipment.

After reading this exception, my point of view says that a ground rod would not be required. Any input is appreciated!

Thank you

A multiwire branch circuit would not terminate in a panel. A feeder terminates in a panel therefore a ground rod or some grounding electrode, is necessary and the grounding electrode conductor would connect only to the equipment grounding conductor.

 

[wwhitney]

I agree the grounding electrode system is required by 250.32.

But I'm a bit unclear on what purpose it actually serves. What is a scenario in which its presence actually enhances safety?

Thanks,
Wayne

 

[Dennis Alwon]

I agree the grounding electrode system is required by 250.32.

But I'm a bit unclear on what purpose it actually serves. What is a scenario in which its presence actually enhances safety?

Thanks,
Wayne

I agree especially since it is only connected to the equipment grounding conductor and not the grounded conductor. I don't see how it can deal with surges as it would back at the main structure

 

[romex jockey]

I agree the grounding electrode system is required by 250.32.

But I'm a bit unclear on what purpose it actually serves. What is a scenario in which its presence actually enhances safety?

Thanks,
Wayne

a fair Q Wayne

in the old days we could do a 3 wire, MBJ in detached structure , now it's all 4 wire, save for a sole branch circuit

if you think on it, a 3 wire scenario is what the poco does every day, even structures mere feet apart

~RJ~

 

[LarryFine]

But I'm a bit unclear on what purpose it actually serves. What is a scenario in which its presence actually enhances safety?

Same as at a service.

 

[don_resqcapt19]

a fair Q Wayne

in the old days we could do a 3 wire, MBJ in detached structure , now it's all 4 wire, save for a sole branch circuit

if you think on it, a 3 wire scenario is what the poco does every day, even structures mere feet apart

~RJ~

But the electrons behave differently depending on who owns them

 

[Dennis Alwon]

Same as at a service.

A bit different as the neutral and grounding are connected together to the rod. At the structure the ground rod is only connected to the equipment grounding conductor. That won't help with surges or spikes, IMO

 

[tom baker]

I agree the grounding electrode system is required by 250.32.

But I'm a bit unclear on what purpose it actually serves. What is a scenario in which its presence actually enhances safety?

Thanks,
Wayne

The intent is lighting and high voltage surge protection, for a 30A or 3000 amp feeder. For a branch circuit, you typically won't have a lot of electrical useage.
Its for the same reason we install a GES for a service.
Rules have been in the code for a long time. We could debate the safety issue, but grounding dates back to the beginning of the code.
So drive 2 and go home, as they say

 

[wwhitney]

The intent is lighting and high voltage surge protection.

OK, so if I consider a lightning strike at various distances from the house and from the outbuilding, which scenario gives greater safety from the ground rods at the outbuilding, vs just relying on the ground rods at the service? I think there may be a scenario here that does give a benefit.

Likewise, unless the high voltage lines are running between the house and the outbuilding, how do ground rods at the outbuilding help? This one I don't see at all.

I'm not arguing for or against the requirement, I'm just trying to understand if it's just historical practice, or if there's a technical benefit I'm missing.

Cheers, Wayne

 

[tom baker]

RE: High voltage lines, the reason goes back to 240.4 performance requirements for grounding and bonding. Its the same rules for services as for separate buildings. Probably more important for services than separate buildings, but there could be a separate building fed by overhead power for a long distance. IMO a lot of Art 250 rules were worked out 100+ years ago and that input from research may be lost.
So perhaps some history and some technical benefit
Whats really important is understand the difference between grounding (ground rods) and bonding (4th green wire) at a separate building and the ground rod won't clear a fault. Many including myself, way back, didn't install ground rods at a feeder as there were 4 wires....

 

[AGreen]

Thank you everyone for the information! It has helped me better understand the situation at hand!