I'm looking at a detached garage a previous electrician fed from the house with 2-2-4 aluminum SER (two hots and a neutral), 60A breaker, 40 feet underground in PVC.

This installation violates NEC 250.33 and 250.142(1). A detached structure requires a 4-wire feeder (two hots, neutral, and equipment grounding conductor) per 250.33(A) and 250.142(1). The existing 2-2-4 SER lacks an equipment grounding conductor.

Immediate issues:

• Bonding screw must be removed (250.142(1) prohibits bonding at the subpanel)
• No ground rod installed (250.33(A) requires grounding electrode system)
• SER cable not rated for direct burial (though it's in PVC, which is acceptable)

Options:

1. Replace feeder with 2-2-2-4 aluminum XHHW in the existing PVC (add equipment grounding conductor)
2. Run separate ground back to house (impractical given existing installation)

Code compliance requires:

• Remove bonding screw at garage panel
• Install ground rod(s) at garage (250.53)
• Add equipment grounding conductor
• Separate neutral and ground bars

Tell the owner this needs a proper 4-wire upgrade. The existing 3-wire setup is unsafe and non-compliant. You cannot legally sign off on the existing installation. Recommend pulling a permit for the feeder replacement and new circuits together.

If budget is a concern, at minimum install a ground rod and remove the bonding screw, but this still won't meet code requirements for a proper EGC.

Do not sign off. This installation has multiple code violations and safety hazards.

Critical Issues:

1. Missing Equipment Grounding Conductor (EGC): 2023 NEC 250.32(A) requires an EGC with all feeders to detached structures. SER cable's bare neutral is not an EGC. You have no ground-fault path back to the house.
2. Improper Bonding: NEC 250.32(B)(1) requires the garage panel to be isolated (bonding screw removed) because you lack an EGC. With the screw installed, neutral current flows on the building's metal parts and earth—a shock/fire hazard.
3. Missing Grounding Electrode System: NEC 250.32(A) requires ground rod(s) at the detached structure. None installed.
4. Undersized Conductor: #4 AL SER is rated 65A (75°C, NEC Table 310.16), but NEC 240.4(B) allows 60A OCPD only if ampacity ≥ 60A. You're at the limit with zero margin; voltage drop over 40' (~3.5% at 60A) is excessive per NEC 210.19(A) FPN.

Required Corrections (Minimum):

• Pull 2-2-4-6 AL SER (adds #6 EGC) or install a separate #10 CU / #8 AL EGC in the PVC (NEC 250.118, 250.122).
• Remove bonding screw in garage panel; install isolated neutral bar.
• Drive two 8-ft ground rods (or one with 25Ω test) at garage, bond to panel ground bar (NEC 250.52, 250.53).
• Re-feed with 60A breaker; verify voltage drop <3% (upsize to 1-1-1-3 AL if needed).

Bottom line: This needs a permit, inspection, and likely a trench re-open. Refuse the sign-off. Document the defects in writing to the owner.