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Single family home built in 1987. Question is regarding the as-built: Is it grandfathered and does not be updated?

There is no neutral-ground bond in the 100A breaker equipped main service disconnect located outside next to the meter box. Only the ground cable to the service panel and a cable to a ground rod are present on a box bonded terminal bar in this box. The neutral just goes thru the service disconnect box, not terminated to anything, going on into the separate meter box.

There is a neutral-ground bond in the garage main lug 20 space service panel, consisting of a #6 copper wire between separate neutral and ground bars.

There is a 2-2-2-4 service entrance cable run from the disconnect box to a service panel in the garage, not in conduit.

Since there is only 1 neutral-ground bonding point the intent of NEC code that no neutral current can flow in the grounding system under normal conditions is satisfied. It just is not bonded where the 2008 and later NEC book says.

My question is since this pre-dates 2008 NEC and there is no new electrical work happening is this grandfathered? Any safety concern?

Addressing the questions in comments:

  • The meter, outdoor box w 100 main breaker, and the 20 space main lug breaker box are all on or in the same building, a single family residence.

  • The metal outdoor box is unlocked and has a 100 Amp 2-pole breaker. That is the means of service disconnect as well as the protective device for the entrance cable. It is located outside adjacent to the outdoor service meter box.

  • The inside box is a main lug 20 space 2-pole load center with separate ground bar and neutral bar. It is located in the residence's garage.

  • The connecting cable is a 2-2-2-4 copper conductor entrance cable, not in conduit. Approximately a 50' wire run inside walls and across attic.

  • The outside box has an AC Disconnect label on its door.

FreeMan
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evolvingpowercat
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1 Answers1

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Pictures would be helpful here; Based on the information alone:

  • Not all AHJ play by the same rules as to what the term "grandfathered" means. But, generally speaking, it should be considered grandfathered-in based on the NEC at the time of construction.

  • Most inspectors aren't going to force you to move the bond even when performing new electrical work unless that work is upstream of the bond or involves replacing the neutral or ground bus.

  • "Any safety concern?" is a VERY ambiguous question. Grounding is a way more complicated topic than even the NEC implies. Speaking very generally: No, it is not a safety concern in optimal circumstances. However, it is far less safe than the bond being made at the main service disconnect both for the occupant and for any electricians who don't promptly cross their t's and dot their i's.

A side note about lightning: You should, however, consider installing a whole house surge protector in your interior panel. Lightning strikes that happen to occur at a position nearly equidistant from your bond to the service transformer gap are going to cause a very short range high-frequency EMP in your indoor panel. It will likely travel down whichever branch has the lowest impedance, using it as an antenna, and fry any electronics along its way.

Chuck Terry
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