Field guide: installing a subpanel, final inspection (edition 6)

Before you call for inspection

Final inspection on a subpanel is pass or fail on details most guys rush. The rough was clean, the feeders are pulled, breakers are in. Now the inspector walks up and starts opening covers. Every torque mark, every bonding screw, every handle tie is fair game.

Walk the job yourself first with a flashlight and a torque screwdriver. Pretend you are the AHJ and you are in a bad mood. If something looks wrong, it is wrong. Fix it before the truck with the county seal pulls up.

Pull the dead front and the main cover. Pull the weatherhead if it is outdoor rated. Inspectors do not want to wait while you chase screws.

Bonding and grounding at the subpanel

This is the number one callback on subpanels. The main bonding jumper or bonding screw in a remote panel must be removed per NEC 250.24(A)(5) and 408.40. Neutral and ground are isolated downstream of the service disconnect. If the green screw is still seated, you fail before the inspector opens a breaker.

Grounded (neutral) conductors land on the insulated neutral bar. Equipment grounding conductors land on the ground bar bonded to the enclosure. One conductor per terminal on the neutral bar, NEC 408.41. Grounds can double up if the manufacturer allows, check the label inside the can.

• Bonding screw removed and bagged inside the panel
• Neutrals and grounds on separate bars
• Separate EGC run with the feeder, not relying on conduit alone for a 4-wire feed
• Ground bar kit installed and bonded to the can
• GEC to local grounding electrode if required by the AHJ for a separate structure, NEC 250.32

Feeder, OCPD, and working space

Confirm the feeder ampacity against the subpanel rating and the upstream breaker. A 100A subpanel fed with #4 copper THHN at 75C terminations checks out per NEC 310.16 and 110.14(C). Aluminum SER needs the 75C column and antioxidant where required by the listing.

Working space in front of the panel is 36 inches deep, 30 inches wide, 6.5 feet high, per NEC 110.26(A). No storage, no shelving, no water heater elbow poking into the zone. Dedicated equipment space above the panel extends 6 feet up or to the structural ceiling, NEC 110.26(E). Sprinkler piping and HVAC duct in that zone will fail you.

If the homeowner stacked Rubbermaid totes in front of the panel while you were on lunch, move them before the inspector arrives. I have watched a clean job fail because a laundry basket was inside the 36 inch box.

Breakers, handle ties, and labeling

Every breaker must be listed for the panel. No Federal Pacific stabs in a Square D can, no classified breakers unless the panel label permits them, NEC 110.3(B). Multi-wire branch circuits need a handle tie or a 2-pole breaker at the point of origin, NEC 210.4(B). This gets missed on shared-neutral kitchen circuits all the time.

AFCI and GFCI protection follows the load, not the panel. Bedrooms, living areas, kitchens, laundry, dishwasher, all still need AFCI per NEC 210.12. GFCI per 210.8 applies to the usual suspects plus the 2020 and later additions like basements and dishwasher outlets. If the subpanel feeds an outbuilding or a kitchen remodel, walk through 210.8 line by line.

• Directory filled out, legible, circuit by circuit, NEC 408.4(A)
• Panel marked with feeder source and location, NEC 408.4(B)
• Arc-fault and ground-fault breakers on the correct circuits
• Handle ties on shared-neutral MWBCs
• No double-tapped breakers unless listed for two conductors

Torque, terminations, and physical protection

NEC 110.14(D) requires torque to the manufacturer spec using a calibrated tool. That means a real torque screwdriver or torque wrench, not a hand tight with a Klein. Mark each lug with a torque seal paint pen so the inspector can see the work was done. Some AHJs now ask to watch you torque a sample in the field.

Check cable entries. Romex clamps snug, no damaged jacket, minimum 1/4 inch of sheath inside the can per NEC 312.5(C). Conduit secured within 3 feet of the enclosure, NEC 344.30 or the chapter for the raceway you used. Unused KOs plugged with a listed closure.

Torque seal is cheap insurance. A yellow dot on every lug tells the inspector you are not guessing, and it tells the next electrician where to start if there is ever a callback.

Final walkthrough checklist

Before you pack the truck, do one loop with the cover off and one with the cover on. Energize, verify voltage phase to phase and phase to neutral, verify no voltage neutral to ground. Any reading above a few hundred millivolts neutral to ground means you have a bond somewhere you did not intend.

1. Bonding screw removed, neutrals and grounds separated
2. Feeder sized and protected per 215.2 and 240.4
3. Working space and dedicated space clear
4. All breakers listed, AFCI and GFCI where required
5. Directory complete and accurate
6. Every lug torqued and marked
7. KOs closed, clamps tight, sheath inside the can
8. Cover flush, no pinched conductors, screws snug

Hand the inspector the permit, the load calc if they want it, and step back. A clean subpanel sells itself in about 90 seconds.