You've hit upon a common area of confusion for electricians and homeowners alike! Let's break down the neutral-ground bonding issue, focusing on your specific scenario and the NEC's evolution.1. Was the above scenario acceptable around 1993?No. In the scenario you described, bonding the neutral and ground at the subpanel in the detached workshop in 1993 was a code violation.

Here's why: Single Point Bonding

The National Electrical Code (NEC) has consistently required that the neutral conductor (the grounded conductor) be bonded to the grounding system (the equipment grounding conductors and earth electrode) at

only one point in the electrical system. This is almost always at the main service panel. Separately Derived Systems

A subpanel in a detached building is not considered a separately derived system unless it's fed by a transformer or generator that creates a new neutral. Your 3-wire feed from the main panel does not create a separately derived system.

Purpose of Separating Neutrals and Grounds

The main reason for separating neutrals and grounds in subpanels is to prevent neutral current from flowing on the equipment grounding conductors. If you bond the neutral at the subpanel, you create a parallel path for neutral current back to the source (the main panel). This current on the grounding conductors can lead to: Nuisance tripping of GFCI breakers Increased risk of electric shock if the grounding conductors are compromised Electromagnetic interference

2. Have bonded neutral & grounds in a detached sub-panel ever been acceptable in the NEC and if yes, what year did that change?

The concept of bonding the neutral and ground only at the main service has been around for a very long time. While the exact wording and section numbers in the NEC have changed over the years, the underlying principle of single-point bonding at the service entrance has been consistent for many decades. It's highly unlikely it would have been permissible in 1923.

Key NEC Changes & Considerations



The main focus changed in 2008 to emphasize the use of 4 conductors for a feeder to an outbuilding: two hots, a neutral, and an equipment grounding conductor. Prior to that, there were provisions for using the neutral as an equipment grounding conductor, but only under very specific and limited circumstances, which would not apply to your scenario. Prior to 2008, specific exceptions allowed for using the neutral conductor as the equipment grounding conductor to supply existing outbuildings when there were no other continuous metallic paths between the buildings (and other conditions were met). This exception is what causes a lot of the confusion. However, the PVC conduit and the RJ11 phone line introduce a metallic path between the buildings, so the exception would not apply to your scenario. Farm Buildings

The NEC provides some allowances for farms, particularly regarding grounding electrode systems, but these are very specific to agricultural buildings and not applicable to a residential workshop. Since you stated it's not a farm, these rules don't apply.

Separately Derived Systems

As mentioned earlier, if the detached building had its own separately derived system (e.g., a generator with its own neutral and grounding electrode system), then bonding the neutral and ground would be required at that separately derived system. But this is not your case.

Why the Confusion? Misinterpretation of Exceptions

The exceptions for pre-2008 installations using the neutral as a grounding conductor are often misunderstood and misapplied.

Local Practices and "Grandfathering"

Some older installations may have been done according to local practices that didn't strictly adhere to the NEC. While these installations may have been "grandfathered in," they don't make the practice correct or safe.

Corrective Action

The scenario you described is not up to code and should be corrected:1.

Separate the Neutral and Ground

Remove the bonding jumper (the wire or strap connecting the neutral bar to the ground bar) in the subpanel at the workshop.2.

Verify a Proper Grounding Electrode System

Ensure that the detached workshop has a proper grounding electrode system (e.g., ground rod(s)) connected to the ground bar in the subpanel.3.

Ensure a 4-Wire Feed

You should be using a 4-wire feed (2 hots, 1 neutral, 1 ground) from the main panel to the subpanel.

In conclusion, bonding the neutral and ground at the subpanel in your detached workshop in 1993 was likely a code violation, and it remains a violation today. It's crucial to correct this to ensure the safety and proper functioning of your electrical system. Flag for review