Field guide: installing a subpanel, tool list (edition 6)

Core hand tools

Every subpanel install starts with the same handful of tools in the pouch. Skip one and you will be walking back to the truck at the worst possible moment. Build the kit around panel work specifically, not general rough-in.

Insulated drivers are non-negotiable when the service is hot next door. 1000V rated, not the bargain bin set that flakes insulation after six months. Klein, Wiha, and Knipex all make field-worthy options. Test them with a meter before trusting them on a live bus.

• 10-in-1 insulated screwdriver (square, Phillips, slotted)
• Linesman pliers, 9-inch, with fish tape puller
• Diagonal cutters and long-nose, both insulated
• Wire strippers rated through 6 AWG solid and stranded
• Cable ripper for NM sheathing
• Tape measure, torpedo level, Sharpie, pencil

Cutting, drilling, and mounting

Subpanels rarely land on virgin drywall. You are cutting into finished framing, fishing through plates, and mounting to studs that are never quite plumb. A hole saw kit from 3/4 inch to 2-1/2 inch handles most knockouts and bore-throughs. Keep a sharp 7/8 inch auger for top plates.

For the can itself, a right-angle drill with a ship auger beats a standard drill every time when you are working inside a stud bay. Cordless is fine for residential, but keep a corded backup for long runs of 1-inch EMT when the battery will not make it.

• Hole saw set with arbor and pilot bits
• Right-angle drill, 1/2 inch chuck
• Reciprocating saw with metal and wood blades
• Knockout punch set, 1/2 inch through 2 inch
• Impact driver with structural screws for mounting

Pre-drill your mounting holes through the panel can before you hang it. Fighting a 40-pound loadcenter while searching for a stud with a self-tapper is how knuckles get skinned.

Conduit and conductor work

Feeder runs to a subpanel almost always involve either EMT, PVC, or SER cable depending on the jurisdiction and whether the run is indoor, outdoor, or buried. NEC 215.2 sets the ampacity requirements, and 310.16 governs conductor sizing. Have both tables bookmarked or keep a pocket reference in the van.

A quality bender, sized for your most common conduit, will save an hour on every job. For residential subpanels on a 60A or 100A feeder, a 3/4 inch or 1 inch hand bender covers most work. Measure your stub-up and back-to-back offsets before you leave the shop.

• Hand bender, 3/4 inch and 1 inch
• PVC cutter and deburring tool
• Fish tape, 50 foot minimum, and fish sticks for short fishes
• Pulling lube, even on short runs with multiple bends
• Cable lugs and a proper crimper for 4 AWG and larger

Testing and verification

Every subpanel gets commissioned the same way. Voltage to ground on each leg, leg-to-leg, neutral-to-ground continuity, and a bond check at the main. If you are feeding the sub from a detached structure, NEC 250.32 requires a grounding electrode system at the subpanel and the neutral stays isolated from ground. Get this wrong and the inspector will have you back out before the sheetrock closes.

A solid multimeter and a non-contact voltage tester are the minimum. A clamp meter earns its keep when you are load-balancing the new panel or verifying existing circuit draw before you extend the feeder.

• True-RMS multimeter with CAT III 600V rating
• Non-contact voltage tester (two of them, for cross-checking)
• Clamp meter for amperage readings
• Receptacle tester with GFCI trip for downstream verification per NEC 210.8
• Megger for long feeder runs or when moisture is suspected

PPE and site setup

Arc flash is real even at 120/240V residential. NFPA 70E Category 2 PPE is overkill for most panel swaps, but safety glasses, cut-resistant gloves, and Class 00 rubber gloves with leather protectors belong in every panel bag. If you are working the main hot, add a face shield and arc-rated long sleeves.

Lockout-tagout is not optional, even on your own work. A single padlock and hasp per disconnect, and a tag with your name and date. NEC does not cover LOTO directly, but OSHA 1910.333 does, and so does every competent AHJ during an inspection walk.

Two voltage testers, always. Test a known live source, test your de-energized conductors, then test the known source again. If the tester dies between steps one and two, you would never know without the third check.

Organization and the punch list

The difference between a two-hour sub install and a full-day slog is usually the pouch layout, not the skill level. Keep breakers, knockout reducers, anti-oxidant compound, and a handful of pigtails pre-made in a dedicated panel bag. You will reach for them every job.

Before you close the cover, run the checklist. Torque every lug to the manufacturer spec, which is printed on the inside of the deadfront per NEC 110.14(D). Label every breaker clearly per NEC 408.4. Photograph the finished panel for your records. The inspector will appreciate it, and so will the next electrician who opens the cover in ten years.

1. Torque all lugs and breaker terminals to spec
2. Verify neutral and ground separation (or bond, at service equipment only)
3. Label all circuits with a legible, permanent directory
4. Install any missing knockout seals
5. Photograph the open panel and the closed deadfront