Distribution Sub-panel

[Don Horn]

The "main" is a single breaker, at or near the meter base, and the distribution panel is some 30 feet away in the home. The only thing running from the "main" 200 amp breaker to the distribution panel is the main electrical service cable (sometimes in conduit but most often not). NOTE: The distribution sub-panel may or may not have a main breaker -- most do not. Am I correct to require the neutral and the ground to be bonded at the main breaker box only -- NOT the distribution sub-panel?

[Jim Port]

The bond should only apply at the service panel.

[Don Horn]

The bond should only apply at the service panel. --- The one by the meter base??

[Jim Port]

The service should be at the first means of disconnect after the meter.

[Jerry Peck]

The neutral is only bonded to ground at the "service equipment", and the service equipment is the panel which has the first disconnecting means. Anything after that is not "service equipment".

In your description, yes, that is the first panel with the "main" (main service disconnect) in it.

From that panel to the other panel the conductors are feeder conductors (not service entrance conductors).

Service entrance conductors are allowed have neutral and ground connected, even allowed to use one conductor for both, neutral conductor doesn't even require insulation (often has it, depending on the type of service entrance conductors).

Feeders are required to have an insulated neutral conductor (when a neutral is needed, a '240 volt only' feeder doesn't need a neutral, a '120 volt/240 volt' feeder needs the neutral) ... and ... a grounding conductor.

[Don Horn]

The neutral is only bonded to ground at the "service equipment", and the service equipment is the panel which has the first disconnecting means. Anything after that is not "service equipment".

In your description, yes, that is the first panel with the "main" (main service disconnect) in it.

From that panel to the other panel the conductors are feeder conductors (not service entrance conductors).

Service entrance conductors are allowed have neutral and ground connected, even allowed to use one conductor for both, neutral conductor doesn't even require insulation (often has it, depending on the type of service entrance conductors).

Feeders are required to have an insulated neutral conductor (when a neutral is needed, a '240 volt only' feeder doesn't need a neutral, a '120 volt/240 volt' feeder needs the neutral) ... and ... a grounding conductor.

Thank you -- that is helpful.

[Jim Hintz]

The "main" is a single breaker, at or near the meter base, and the distribution panel is some 30 feet away in the home. The only thing running from the "main" 200 amp breaker to the distribution panel is the main electrical service cable (sometimes in conduit but most often not). NOTE: The distribution sub-panel may or may not have a main breaker -- most do not. Am I correct to require the neutral and the ground to be bonded at the main breaker box only -- NOT the distribution sub-panel?

Just to provide an example: If you ever inspect the "Electrical Panel" inside a Manufactured Home or a Condo - they are 99.9% of the time a "Remote" Panel / "sub" Panel (Sorry Jerry)... The "Main Disconnect" is at the Service Entrance / Power Meter where "Bonding" can occur. When a Manufactured Home site is being prepped, the workers need power so there is usually a pole with a meter and a means of disconnect...With condos, the meters are usually in a group at the end of the building with a main breaker for each unit beneath them.....

[Don Horn]

Thank you. Yes, I have inspected several manufactured homes (75% Clayton in this area) and they are all wired with the inside distribution panel treated as a sub-panel. I talked with the local code inspector and learned IF the service from the "main" to the distribution "sub-panel" is run in EMT (any metal conduit) with grounding bushings properly installed at each end, a "3-wire" surface is allowed between the "main" and the sub-panel.

[Jerry Peck]

I talked with the local code inspector and learned IF the service from the "main" to the distribution "sub-panel" is run in EMT (any metal conduit) with grounding bushings properly installed at each end, a "3-wire" surface is allowed between the "main" and the sub-panel.

That's because what you described is a "4-wire" installation - the EMT with grounding bushings is "the" "grounding conductor" ... aka ... the 4th wire ... oops ... the 4th CONDUCTOR. :)

[Don Horn]

I'm thinking the use of EMT and grounding bushings just extended the size of the "main panel" to include the conduit run. Not really (technically?) a 4 conductor installation.

[ROBERT YOUNG]

That's because what you described is a "4-wire" installation - the EMT with grounding bushings is "the" "grounding conductor" ... aka ... the 4th wire ... oops ... the 4th CONDUCTOR. :)
I think Elizabeth would do well reading that post. "the 4th wire ... oops ... the 4th CONDUCTOR."

[Jerry Peck]

I'm thinking the use of EMT and grounding bushings just extended the size of the "main panel" to include the conduit run.

Nope. :)


Not really (technically?) a 4 conductor installation.

Yeppers, it is "technically" the 4th conductor of the "feeder conductors" which "feeds" the next panel downstream.

The feeder conductors are required to have: insulated ungrounded conductors (the 'hot' 'wires'); insulated neutral conductor (the 'neutral' 'wire' ... if and only if the feeder conductors are supplying a 120 volt / 240 volt load or panel ... the 'neutral' is not required if the load or panel the feeders supply is only 240v); and an equipment grounding conductor (which may be insulated or uninsulated, and the metal EMT in your description is that "equipment grounding conductor" ... that '4th wire').

The "service equipment" is, and remains, where that first disconnect is, the "service equipment" is within that enclosure which contains that first disconnect which shuts off, "de-energizes" the service to the structure beyond that first disconnect.

It can get more complicated in that up to 6 main service disconnects are allowed ... with conditions ...

... and even a 7th main service disconnect is allowed if there is a fire pump (don't want to shut off the fire pump when disconnecting power to the building during a fire, you want that fire pump to run until it burns itself up, if that be the case, better to allow the fire pump to burn itself up if it can run long enough to save the occupants and the building - actually, it really isn't even about saving "the building", it is about saving "the occupants").

- - - Updated - - -


I think Elizabeth would do well reading that post. "the 4th wire ... oops ... the 4th CONDUCTOR."

I'm going to have to pull a permit to 're-conductor' my house instead of 're-wire' it and see what the building department says.
:peep: