ungrounded sub panel

[Don Hawley]

We frequently find sub panels in detached garages and sheds fed by 220v 3 wire feeds without a ground wire from the main breaker box. If the proper solution is to provide a separate ground rod and ground the sub panel; do we separate the grounds and isolate the neutral or bond the neutrals and grounds to the box as if it were a new primary panel?

[Jim Port]

With a 3 wire feeder the panel is again bonded like a service panel. There can be no metallic path between the two buildings.

[Derek Guridi]

To add to what Jim posted.

All detached structures with a 120/240V panel need a Grounding Electrode System-rods, pipe, etc-whether 3 wire or 4 wire.

3 wire feeders to detached structures for a 120/240 panel were last allowed under the 2005 NEC. 2008 and later installs require a 4 wire feeder.

Existing systems are grandfathered.

[Scott Patterson]

To add to what Jim posted.

All detached structures with a 120/240V panel need a Grounding Electrode System-rods, pipe, etc-whether 3 wire or 4 wire.

3 wire feeders to detached structures for a 120/240 panel were last allowed under the 2005 NEC. 2008 and later installs require a 4 wire feeder.

Existing systems are grandfathered.

Derek, can you cite a reliable source where it states this is "grandfathered"?

[Jerry Peck]

To add to what Jim posted.

All detached structures with a 120/240V panel need a Grounding Electrode System-rods, pipe, etc-whether 3 wire or 4 wire.

3 wire feeders to detached structures for a 120/240 panel were last allowed under the 2005 NEC. 2008 and later installs require a 4 wire feeder.

Existing systems are grandfathered.


Derek, can you cite a reliable source where it states this is "grandfathered"?

Scott,

It is "grandfathered in" by virtue of the fact that, when it was constructed, it was allowed.

Codes do not require retroactive compliance - that would be a horrendous undertaking ... to have to update every building every time there was a code change. Thus, legally existing buildings are allowed to remain as they legally existed at the time of construction ... i.e., existing building are "grandfathered in" as they were legally existing - such as three-wire feeders to a remote panel at a remote building (a detached garage for example).

Even the "retroactive" sections of the NEC (and there are a few) do not affect a legally existing system as it was constructed at the time. The "retroactive" sections of the NEC only affect "changes" which took place, have taken place, are are taking place: i.e., over-fusing Edison base fuses are required to have those safety-fuse adapters installed to prevent overfusing ... receptacles which are "replaced" in locations which now require GFCI protection but did not require GFCI 'back then' are now required to be GFCI protected - but a non-GFCI receptacle, original, in a now-required to have GFCI protection is allowed to remain ... non-grounding type two-prong receptacles are allowed to be remain, but when "replaced" ... we all now many instances where when something is "replaced" it needs to meet current code, but when still left "original as it was legally constructed" it is allowed to remain as it was and still is.

That is commonly called "grandfathered in", albeit the correct terminology would be "legally existing is allowed to remain as legally existing" (if it was never "legally existing", i.e., did not meet code at the time, then it needs to meet the current code when it is discovered that it was not "legally existing").

- - - Updated - - -

(continuing from my previous post)

From the IRC: (underlining is mine)
- R102.7 Existing structures.
- - The legal occupancy of any structure existing on the date of adoption of this code shall be permitted to continue without change, except as is specifically covered in this code, the International Property Maintenance Code or the International Fire Code, or as is deemed necessary by the building official for the general safety and welfare of the occupants and the public.

(The it kicks in some stuff about the Property Maintenance Code and Fire Code, but that is only applicable if so adopted.)

Basically, if it was legally existing ... it is permitted to remain so without changes.

[Jim Port]

Scott, there is a note in Article 215 IIRC, that says an existing 3 wire feeder can remain. New feeders under the 08 or later need to be 4 wires.

[Don Hawley]

What do you recommend we write in the HI report when we find this situation?

[Marc M]

Scott, there is a note in Article 215 IIRC, that says an existing 3 wire feeder can remain. New feeders under the 08 or later need to be 4 wires.

Hey jim, sorry to bug, but do you have the link to that article?

[Gunnar Alquist]

What do you recommend we write in the HI report when we find this situation?

Don,

The problem is in that note that Jim made about no metallic path. This would mean actually knowing if there was a metallic path back to the location of the service equipment. Buried piping, telephone cable, metal fence, whatever. Too often, we don't know. Better to make a note and defer.

What I do is note that grounding is currently required to go back to the service equipment and defer to an electrical contractor. Let the electrical contractor sort it out. If you notice a direct path, even better.

[Jerry Peck]

What I do is note that grounding is currently required to go back to the service equipment and defer to an electrical contractor. Let the electrical contractor sort it out. If you notice a direct path, even better.

I would state it differently because, by "defer" that gives you "no response option" when the electrical contractor says something you disagree with, so instead of "defer" I would state to have electrical contractor document that no metallic path is present between the two structures, or properly rewire if there is a metallic path between the two structures.

That presents the condition you found and the two proper options for that condition.

[Gunnar Alquist]

That presents the condition you found and the two proper options for that condition.

Fair enough. :thumb:

[Lorne Wolfe]

With a 3 wire feeder the panel is again bonded like a service panel. There can be no metallic path between the two buildings.

How can you have "no metallic path between the two buildings"? All 3 wires run directly between the two buildings. The neutral wire would be bonded to the main service panel in the house and also bonded to the sub panel in the outbuilding.

Lorne

[Rollie Meyers]

How can you have "no metallic path between the two buildings"? All 3 wires run directly between the two buildings. The neutral wire would be bonded to the main service panel in the house and also bonded to the sub panel in the outbuilding.

Lorne


The correct wording is no other metallic paths, or no continuous metallic paths bonded to the grounding systems in each building or structure involved. You do not want metallic water lines or similar items between the buildings.

[Jerry Peck]

The correct wording is no other metallic paths, or no continuous metallic paths bonded to the grounding systems in each building or structure involved. You do not want metallic water lines or similar items between the buildings.

Rollie,

Are you saying that the code says 'metallic paths bonded to the grounding systems'?

My recollection is no 'metallic paths' between the two buildings ... whether or not the metallic paths are bonded to anything.