Most homeowners who DIY electrical work do fine. But a small set of mistakes shows up again and again — usually months or years later, often during a home sale or insurance review. Here are the ones we see most.
1. No permit on a circuit that needed one
Adding a new circuit (EV charger, hot tub, sub-panel) without an ESA permit. The work might be fine technically, but the lack of a permit gets flagged in a home inspection, voids insurance for related claims, and forces you to either get retroactive inspection ($$$) or rip it out at sale time.
Avoid: Pull the permit before the work. ESA will inspect a homeowner-done install if you’re also the qualified person doing it.
2. Wrong wire size for the load
Using 14-gauge wire on what should be a 20A circuit, or undersizing the feeder for a sub-panel. Causes nuisance breaker trips at best, fires at worst.
Avoid: Look up the OESC ampacity table for your wire type, account for derating (multiple wires in conduit), and round up.
3. Aluminum-rated terminations on copper wire (or vice-versa)
CO/ALR connectors are designed for aluminum. Putting copper in CO/ALR-only locations or aluminum in copper-only locations causes loose connections over time. Loose connections cause fires.
Avoid: Use the right device, or pigtail correctly through a proper transition connector (AlumiConn for aluminum to copper).
4. Outlet strap not grounded properly
Using the receptacle’s screw threads as ground (through the metal box) instead of a dedicated ground wire to the box. Code-fail and a real shock risk.
Avoid: Pigtail a 6-inch ground wire to the metal box and the receptacle ground screw separately.
5. Backstabbed outlets and switches
Cheap and fast: push the wire into the back “quickwire” hole. Works for a few years, then the spring connection loosens, the outlet overheats, and you have intermittent power or scorched plastic.
Avoid: Use the side terminal screws. Strip wire, wrap clockwise, tighten firmly.
6. Tandem breakers in panels that don’t allow them
Some panels accept tandem breakers (two breakers in one slot) only in specific labelled positions. Putting them in the wrong slots overloads the bus bar.
Avoid: Read the panel label inside the door — it shows allowed positions.
7. No box (or wrong box) for connections
Twisting wires together inside a wall without an accessible junction box. Code-fail and a common cause of hidden electrical fires.
Avoid: Every splice goes in an accessible junction box. Junction boxes can’t be drywalled over — they need cover access.
8. Wrong screw torque on panel lugs and breakers
Hand-tight isn’t enough. Loose lugs heat up, arc, and burn. Some breakers (notably Square D QO) specify a torque in inch-pounds on the label.
Avoid: Use a torque screwdriver to the manufacturer’s spec, not feel.
9. Adding load to a Federal Pacific / Stab-Lok panel
The breakers don’t reliably trip. Adding any new load increases the chance one trips when it shouldn’t — or doesn’t when it should.
Avoid: Replace the panel before adding load. See why.
If you find one of these in your home
It’s never too late to fix. Start a quote and mention what you found — we’ll prioritise the safety items and quote a fix.