Originally Posted By: roconnor This post was automatically imported from our archived forum.
" to describe a panel that is downstream from what I think of as a Service Panel (has the main service disconnect) or a Distribution Panel (which does not have the main service disconnect). Those terms are pretty common, and I believe the NEC handbook also uses the term “sub panel”. I think the issue was use of the converse term, which is “Main Panel” … I agree that is a poor term to use.
jpope wrote:
I understand the requirement, I am left wondering about the exception ...
Could this exception be for a sub panel in a separate building equipped with a GES?
I agree with Greg that the answer is Yes, but with some clarifications. There are basically two (2) options for sub-panels in a separate building on the same property:
1) Run a feeder with hot, neutral, and ground wires to the remote sub-panel ... and keep the neutral and ground isolated (isolated neutral sub-panel).
2) Run a feeder with only hot and neutral wires to the remote sub-panel ... and connect the neutral and ground wires at that sub-panel (re-grounded sub-panel).
I think Option #2 is the exception to the isolated neutral rule you are referring to ... and that ONLY applies to a panel in a remote building with a separate feeder without a ground wire or metal conduit, and a connection to earth. Hope that helps ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)
[Both with a connection to earth (GES) ... see below]
-- Robert O'Connor, PE
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Originally Posted By: roconnor This post was automatically imported from our archived forum.
Greg Fretwell wrote:
Actually any building fed from another needs a grounding electrode system, unless it is just a single branch circuit.
Not sure how that applies. For a remote building (e.g. garage) I usually just see the regrounded subpanel with a separate earth connection (GES) ... but if there is only a single branch feeder to a remote building, couldn't that be installed without a separate GES if a ground wire is run with the feeder per NEC 250.32A-Exception. Where are ya going with that?
[Check that ... see below]
-- Robert O'Connor, PE
Eagle Engineering ?
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I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Greg Fretwell This post was automatically imported from our archived forum.
I am “going” to explain the difference between a branch circuit and a feeder. If there is a sub panel, or any other overcurrent device down stream is is not a branch circuit, it is a feeder.
250.32(A) ex only applies to a single branch circuit. If you have a panel in the remote building it is a feeder and you need a GES.
The exception is for a case where you run a single circuit out to the garage for lights and maybe a receptacle or two.
The "hold your nose" cheat is to run a 20a 240v 4 wire "single branch circuit" and split it into a 240/120v multiwire in the garage. That gives you the equivilent of 240v and two 120v circuits, all counted as "one branch circuit".
Originally Posted By: dvalley This post was automatically imported from our archived forum.
Quote:
The exception is for a case where you run a single circuit out to the garage for lights and maybe a receptacle or two.
makes my reporting a little different.
So if I see a feeder going to only one 20 amp breaker (single branch circuit) in a separate building, it's OK to see a missing GES as long as every neutral is floating.
If I see more than one breaker (multiple branch circuits), and the panel is not grounded with its own GES, then I would red flag it as I have been. Grounds and neutrals can be mixed in this situation.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Greg Fretwell wrote:
250.32(A) ex only applies to a single branch circuit. If you have a panel in the remote building it is a feeder and you need a GES.
Hmmmm ... I usually see the re-grounded sub-panel with a separate earth connection. Had thought that running a ground wire with the feeder was an option to installing the separate earth connection by considering the supply a branch circuit feeder (branch circuit off the service panel). But reading that again I think thats a stretch, and you are right that a separate earth connection (GES) would be required anyway for a remote isolated neutral sub-panel.
dvalley wrote:
If I see more than one breaker (multiple branch circuits), and the panel is not grounded with its own GES, then I would red flag it as I have been. Grounds and neutrals can be mixed in this situation.
Grounds and neutrals can not be mixed if it is an isolated neutral sub-panel (Option #1 in my prior post).
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: jmyers This post was automatically imported from our archived forum.
At 150 feet away from the building, I would hardly call that readily accessible. In the event I would have an emergency and the need to turn the power off would arise, I would probably have a heart attack having to run 150 feet to turn off the power.
I agree there is no stated distance in the NEC, however I would hardly call that readily accessible. It would also be subject to vandalism, stolen energy and most likely, a sizeable voltage drop given that distance. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)