Thread: Neutral and ground separation not always required in remote panels.

I was talking with an experienced electrician today and would like some additional clarification. It was always my understanding that ground wires had to be separated from neutrals and bonded to panel in any remote distribution panels (aka sub panel). I was told by the electrician that it's only required when the downstream panel is located in the home, and that remote panels in any detached outbuilding do not require the grounds to be separated.

The photo is a remote panel in detached garage, it's fed from the home's main service panel.

Check out NEC 250.32, were under the 2011 edition in WI.

I think prior to the 2008 NEC you could wire this way, but it still had requirements. For example, If you had a switch in the home that turned a light on at the garage you had to separate. Same with the running of metal gas pipe to the garage for a heater, it's another metallic pathway.

The 2011 NEC requires separation with a couple exemptions: A single branch-circuit disconnect at the garage (with a ground), or a previous code edition compliant install, as long as other requirements are still being met, 250.32(B)(1) exceptions.

If this is a detached structure with no metal water pipes or phone/tv cables it was allowed. However, if that green ground heads back to the main panel, separating the two is a good idea.

I did a house the other day that had a remote distribution panel (sub panel) for an attached wing. This panel was fed by an insulated three conductor cable through the crawlspaces. Obviously, neutrals and grounds were combined in this remote panel. I called it out, said review with Electrical Contractor for safety, etc.

Home Owner asked me if there was any type of single conductor ground wire (solid/stranded/insulated or not) that could be run to this remote panel without being in conduit. I told him I didn't know.

In other words, is there a way to upgrade the feed to this remote panel, by adding a ground conductor and leaving the existing 3 conductor feed.

There is a lot of intellectual electrical fire power on this Forum, curious as to the answer.

Thanks, John P, North Carolina

Originally Posted by JOHN PAVAN

I did a house the other day that had a remote distribution panel (sub panel) for an attached wing. This panel was fed by an insulated three conductor cable through the crawlspaces. Obviously, neutrals and grounds were combined in this remote panel. I called it out, said review with Electrical Contractor for safety, etc.

Home Owner asked me if there was any type of single conductor ground wire (solid/stranded/insulated or not) that could be run to this remote panel without being in conduit. I told him I didn't know.

In other words, is there a way to upgrade the feed to this remote panel, by adding a ground conductor and leaving the existing 3 conductor feed.

Yes. As I read your description, the sub is fed through the crawlspace. No need for conductors in a crawl to be in conduit.

In regards to having a feeder to a sub panel in a detached building:
As far as I can recall - you were ( and still are) required to separate the grounded ( neutral) and the grounding ( ground) in a sub panel in a detached structure.
The part that has changed over the years is the requirement for the 4th conductor, the grounding conductor ( ground). You used to be able to pull the hots and neutrals only then drive a ground rod for the ground.
Now you pull the hots, neutral AND a ground plus drive the ground rod.

More information is needed.

We know:
- The remote panel is feeding an attached wing of the same structure.
- The cable feeding that remote panel is an " insulated three conductor cable"

What we do not know:
- Those three conductors in that cable ... all three conductors are insulated, or only two are insulated?
- If all three conductors are insulated, is there an outer uninsulated conductor wrapping the inner three insulated conductors, all within the same outer sheath?

The grounding conductor, if missing (i.e., if there are three insulated conductors *only* in that cable) is required to be in the same cable (within the same sheath), so, no, there is no easy way to correct that other than replacing the cable with a proper cable (three insulated conductors and one conductor for grounding which may be insulated or uninsulated).

One thing they could do is convert to 120 volts only for the remote panel.

But for someone to make such a fundamental error in choosing a 3-wire feeder makes me think that panel was installed by an amateur with no permit. Not good.

Originally Posted by Jerry Peck

The grounding conductor, if missing (i.e., if there are three insulated conductors *only* in that cable) is required to be in the same cable (within the same sheath), so, no, there is no easy way to correct that other than replacing the cable with a proper cable (three insulated conductors and one conductor for grounding which may be insulated or uninsulated).

Live and learn. This is why I like this forum. Didn't realize that. I thought that adding a grounding conductor would be no problem. You might ask for a variance from your local AHJ to allow a separate grounding conductor.

Regardless of the remote structures feed, a exterior light must be provided for at the entrance to the structure. If it is a garage, the garage door is not considered to be the entrance.

The only way you can use the primary grounding system is if the structure is connected to the same building as the man system.

If the structure is remote structure, and it is a single or Multiwire connection then you can e the same ground connection.

However, if you are feeding a panelboard, hen it must be a four wire feed and Neutral and ground must be isolated. The remote structure's grounding system is to protect the remote structure.

Also, if the grounds were to be connected together and if they were at different potentials you could end up with an unwanted ground loop current.

- - - Updated - - -

Regardless of the remote structures feed, a exterior light must be provided for at the entrance to the structure. If it a garage, the garage door is not considered to be the entrance.

The only way you can use the primary grounding system is if the structure is connected to the same building as the man system.

If the structure is remote structure, and it is a single or Multiwire connection then you can e the same ground connection.

However, if you are feeding a panelboard, hen it must be a four wire feed and Neutral and ground must be isolated. The remote structure's grounding system is to protect the remote structure.

Also, if the grounds were to be connected together and if they were at different potentials you could end up with an unwanted ground loop current.

The feeder has a ground so ground and neutral must be separate then.


Detached structures with no metallic paths back to the building were allowed a 3 ire feed up until recently.

Originally Posted by Mbrooke

The feeder has a ground so ground and neutral must be separate then.

I think you are referring to the photo is post #1, that question ended with post #3.

A new related question began with post #4 and there is, that I recall seeing, no photo for the recent question.

Yes, in the original post of the original question, there is a ground shown.

In newer construction, I often see a separate panel in a detached garage or other detached structures (workshops, etc.) that are feed from the main house service equipment. These remote panels have separate ground connections (ground rods) and sometimes the ground and neutral bus bars are separated and other times these are connected to a common bus.

So just for clarification on this thread:

1. Do panels in detached structures require separate ground rods? (fed from remote service panel)
2. Should the ground and neutral connections in these remote panels always be isolated?
3. Is there any situation where the ground and neutral connections for these remote type panels in detached structures should be common?

- - - Updated - - -

In newer construction, I often see a separate panel in a detached garage or other detached structures (workshops, etc.) that are feed from the main house service equipment. These remote panels have separate ground connections (ground rods) and sometimes the ground and neutral bus bars are separated and other times these are connected to a common bus.

So just for clarification on this thread:

1. Do panels in detached structures require separate ground rods? (fed from remote service panel)
2. Should the ground and neutral connections in these remote panels always be isolated?
3. Is there any situation where the ground and neutral connections for these remote type panels in detached structures should be common?

- - - Updated - - -

In newer construction, I often see a separate panel in a detached garage or other detached structures (workshops, etc.) that are feed from the main house service equipment. These remote panels have separate ground connections (ground rods) and sometimes the ground and neutral bus bars are separated and other times these are connected to a common bus.

So just for clarification on this thread:

1. Do panels in detached structures require separate ground rods? (fed from remote service panel)
2. Should the ground and neutral connections in these remote panels always be isolated?
3. Is there any situation where the ground and neutral connections for these remote type panels in detached structures should be common?

Originally Posted by Ken Amelin

In newer construction, I often see a separate panel in a detached garage or other detached structures (workshops, etc.) that are feed from the main house service equipment. These remote panels have separate ground connections (ground rods) and sometimes the ground and neutral bus bars are separated and other times these are connected to a common bus.

So just for clarification on this thread:

1. Do panels in detached structures require separate ground rods? (fed from remote service panel)
2. Should the ground and neutral connections in these remote panels always be isolated?
3. Is there any situation where the ground and neutral connections for these remote type panels in detached structures should be common?

1) Yes, detached structures requires separate grounding electrode systems (UFER, ground rods, etc.)

2) Yes, the neutral should be isolated from ground in those structures.

3) No, not that I can think of (maybe Jim P or someone else will post one that I am not remembering right now).