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Outlet circuit: three outlets on a 20 A breaker

Bench build · Power, transformers and three-phase · Intermediate · about 35 minutes

Three duplex outlets on 3.5 mm² wire and a 20 A breaker, with a TV, refrigerator, rice cooker, kettle and flat iron plugged in. Convenience outlets are daisy-chained on one branch circuit: the line and neutral run from outlet to outlet on the brass screws. The breaker protects the CABLE, so the cable must be rated for the breaker: 3.5 mm² (12 AWG) for 20 A. Philippine Electrical Code practice: lighting on 2.0 mm² (14 AWG) and a 15–20 A breaker (here 10 A), outlets on 3.5 mm² (12 AWG) and a 20 A breaker, big appliances on their own circuit.

Outlet circuit: three outlets on a 20 A breaker: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. Normal load: TV, refrigerator and rice cooker
  2. Voltage at the last outlet under load
  3. Kettle and iron on too (3.35 kW, 15 A): the breaker holds
  4. Overload: a space heater and a second kettle on an extension (31 A)
  5. Short circuit in a damaged plug at outlet 3
  6. Cable sized for the breaker

How it works

What it does: Three duplex outlets on 3.5 mm² wire and a 20 A breaker, with a TV, refrigerator, rice cooker, kettle and flat iron plugged in.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

Overloaded outlet circuits and undersized extension cords are among the commonest causes of house fires. A breaker that keeps tripping is doing its job: the fix is another circuit, not a bigger breaker.

More builds: power, transformers and three-phase