I was a home this morning and I ran into an unusual situation with a 4 conductor 120 VAC service supplying the garage. The height above grade was 8-1/2 to 9 feet. Since this a 4-conductor circuit, the neutrals and grounds are combined in the remote panel. My concern is the height above grade. I know the requirements for a service for the dwelling, but I have not run across anything for this situation regarding the height.
Looking for more definitive answer. I look at it being a safety concern not to mention the lack of drip loop at the dwelling.
I am curious about that too. Was it a 4-wire 120/240V feeder (H-H-N-G), and then only 3 of the wires were used for a 120V remote subpanel (H-N-G)?
The neutrals and grounds should not be connected if a ground wire is run with the feeder (or metal conduit is used that connect the two panels). Otherwise you could get current on that ground wire (parallel neutral path) … :shock:
There are basically 2 ways to do a remote subpanel (NEC 250.32 … see figures):
Connect the grounds between the service panel and remote subpanel (e.g. feeder ground wire or metal conduit connecting the panels). Then isolate the neutrals and grounds at the remote subpanel.
Do not connect the grounds between the service panel and remote subpanel (e.g. no feeder ground wire or metal conduit connecting the panels). Then the grounds and neutrals are connected at the remote subpanel.
And a separate earth ground (GES) is required for either remote subpanel option.
Yes, I should have noted there are limitations now if the latest NEC has been adopted. The change applies to all new buildings on the 2008 NEC I believe, which many areas haven’t even adopted yet. But even then there are still the two options for existing building systems where a remote building panel has been added. Home inspectors may find either option on inspections of existing buildings.
For an existing house I don’t think the second option (no ground with the feeder) is really a safety issue an inspector needs to comment on, even though it wouldn’t be permitted for all new construction under the latest NEC. My understanding is the change was made because you can have larger remote buildings where there is a remote subpanel without the ground on the feeder, and then another remote panel feeder is run with the ground … and then the two systems are somehow connected (e.g. both are bonded to building steel or metal water lines).