Okay, let's break this down. You've identified a serious issue, and it's good you're seeking guidance. This setup presents several safety hazards related to grounding and bonding. Here's a comprehensive assessment and recommendations, focusing on safety and compliance

Here's a breakdown of the problems:
Subpanel #2 (Older Section)

This is the most critical issue. Using only three wires (two hots and a neutral) to feed a subpanel from the main house panel (your first subpanel) is

not compliant with current codes and was likely never compliant when installed in the 1980s (with some rare exceptions for ranges and dryers). Connecting the neutral and ground at this subpanel creates a parallel neutral path, which is extremely dangerous. Here's why: Neutral Current on Ground

Neutral current, which should only flow on the neutral conductor, will now also flow on the grounding conductor. This can energize metal parts of the electrical system (enclosures, conduit, etc.), creating a shock hazard.

False Sense of Security

If a ground fault occurs, the neutral current on the grounding conductors can make it difficult for overcurrent protection (breakers) to trip quickly, delaying the disconnection of the circuit.

Electromagnetic Interference (EMI)

Neutral current on the grounding system can generate EMI, potentially affecting sensitive electronic equipment.

Subpanel #3 (Detached Building)

While you have ground rods at this panel and have separated the neutral and ground, the problem is it is being fed by the 2nd subpanel using an improper 3-wire feed. The ground rods provide a local ground potential, but they aren't an adequate grounding path back to the main service. The ground fault current can not properly flow through the earth back to the source, preventing the breaker from tripping in a fault condition.

Code References (NEC - National Electrical Code - Consult your local electrical codes as they may differ)



NEC 250.32

This section outlines the grounding and bonding requirements for outbuildings (detached structures). It generally requires a grounding electrode system (ground rods) and a grounding conductor run with the circuit conductors from the main building to the outbuilding.

NEC 250.6

This section says you can't intentionally use the earth as an effective fault current path.

NEC 300.3(B)

All conductors of the circuit, including the grounding conductors, must be installed in the same raceway or cable.

NEC 250.24(A)(5)

For systems supplied by a service, the grounded conductor shall not be connected to normally non-current-carrying metal parts of equipment on the load side of the service disconnecting means

Here's what you NEED to do


Correcting Subpanel #2 (Older Section)

This is the highest priority.

Best Solution (and Required by Code): Run a separate grounding conductor (equipment grounding conductor, EGC) from the first subpanel (the main house panel) to this second subpanel. This is required by code and is the safest approach. This conductor must be sized appropriately according to NEC Table 250.122 based on the size of the circuit breaker protecting the feeder. STOP: Do NOT Connect the Neutral to Ground

After running the ground wire, completely disconnect the neutral from the ground at the subpanel. The neutral should be isolated on its own bus bar.

Inspect & Repair

Carefully inspect the existing wiring for any damage or deterioration and repair as needed.2.

Correcting Subpanel #3 (Detached Building)



Dependency on #2

The correction for this subpanel is directly dependent on how you corrected Subpanel #2.

Scenario 1: Subpanel #2 is properly grounded

If you ran a separate ground wire to the 2nd subpanel and disconnected the neutral from ground, you also need to run a 4-wire cable (two hots, neutral, and ground) from the second subpanel to this third subpanel. You'll then use the grounding conductor in that cable to connect to the ground bar, which is connected to your ground rods. The neutral remains isolated from ground.

Scenario 2: You still have a 3-wire feed to subpanel #2: This isn't an option. You can not properly or safely supply a detached building using a 3 wire feed.

Alternatives and Considerations (and why they're generally not acceptable)



"Bootleg Ground"

This is where you jumper the ground and neutral together at the receptacle in the older subpanel, which can be very dangerous.

Important Safety Precautions



De-energize the Circuit

Always turn off the power at the breaker before working on any electrical wiring. Double-check with a non-contact voltage tester to ensure the circuit is dead.

Lockout/Tagout

Use a lockout/tagout device on the breaker to prevent someone from accidentally turning the power back on while you're working.

Proper Tools

Use insulated tools designed for electrical work.

Personal Protective Equipment (PPE)

Wear safety glasses and insulated gloves.

Professional Assistance

If you are unsure about any part of this process, hire a qualified and licensed electrician*. Electrical work can be dangerous, and mistakes can have serious consequences.

In summary, the 3-wire feeds to your subpanels are hazardous and need to be corrected. The best and safest approach is to run a separate ground wire from the main house panel to the 2nd subpanel. The earth and ground rods can not be used as the primary path for fault current. You need a properly sized equipment grounding conductor.

Good luck, and stay safe! Flag for review