Test before you touch
Before you replace a receptacle, you prove that nothing in the box is live. You turn the breaker off and lock it, check the tester, test every wire, and check the tester again. You see what goes wrong when a tester fails or a label is wrong.
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What to try
- 1On Done right, press each step in order from Breaker off to Hands on. Every wire reads zero, and the tester works before and after.
- 2Pick Broken lead and press Check tester. The tester reads zero on a receptacle you know is live, so you cannot trust it.
- 3Pick Wrong breaker and step through to Test. The panel label is wrong, and the box still reads 120 volts.
NEC 2026 sections it covers
- 250.148(C)
- In a metal box, a ground pigtail runs to the box's green screw.
- 210.4(B)
- Breakers on a shared neutral shut off together.
- 300.15(B)
- Pulling a receptacle must not open the white wire.
- 110.25
- When a disconnect must lock off, this covers how the lock holds it off. The test itself is trade practice.
Section numbers only. Read the full text in your code book. Temperatures and times in the visual are teaching models.
See something wrong? Tell us and we will check it against the code.
More visuals
- Breaker and wirePlug in loads and watch the wire heat up when the breaker is too big for it.
- What a GFCI sensesCurrent goes out and comes back. See what happens when a little goes missing through a person.
- What an AFCI sensesA crushed cord arcs. Watch the shape of the current change, and the breaker count it.