Water heater circuit: 3.5 kW on 5.5 mm² and a 30 A breaker
Mains through a 30 A breaker and 5.5 mm² wire to a 3.5 kW storage water heater. The tests raise it to 5 kW and try the wrong wire. An instant or storage water heater is the biggest load in most Filipino homes: 3.5 kW is 16 A all the time it heats, and a 5 kW unit is 23 A. It gets its own circuit, 5.5 mm² THHN (10 AWG) on a 30 A breaker, and 8.0 mm² on 40 A for 5 kW. Put it on the 2.0 mm² lighting wire and the wire runs hot long before the breaker notices. 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.
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Parts list
Test procedure
Each test has an expected value and a pass range, like a factory test sheet:
- 3.5 kW heating
- Cable sized for the breaker
- A 5 kW heater on the same 30 A circuit
- 5 kW on a 15 A breaker (the old lighting breaker)
- 3.5 kW on 2.0 mm² lighting wire with the 30 A breaker
How it works
What it does: Mains through a 30 A breaker and 5.5 mm² wire to a 3.5 kW storage water heater. The tests raise it to 5 kW and try the wrong wire.
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
Water heater na lagi nagti-trip? Either it shares a circuit, or the breaker is too small for the element. Hot wire with no trip is the dangerous case: a breaker protects the cable only when the cable is rated for the breaker.
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- RCD protection: someone touches a live wire
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