Lesson 5
Heating Elements and Trips
Work out an element's resistance from its power rating, see why heat needs resistance, and read what an RCD trip during heating does and doesn't tell you.
A 2 kW element is a 26-ohm wire
Take a washing-machine heating element rated at 2,000 W on 230 V. Those two numbers are enough to work out the element itself, because power, voltage and resistance are linked: resistance = voltage² ÷ power. So 230 × 230 ÷ 2,000 ≈ 26 ohms (Ω). A 2 kW element is, in effect, a 26-ohm wire.
That resistance is the working part, not a flaw. Pushing current through a wire that resists it turns electrical energy into heat, the way rubbing your hands together turns effort into warmth: the friction is the point. A heater with no resistance would make no useful heat; it would just be a short circuit. Watts, Amps, and Why Wires Melt covers power and current in more detail.
The wire is a coil packed in fine mineral powder inside a metal tube, the sheath. The powder has two jobs: let the heat out to the water, and keep the current in the coil. Limescale on the sheath gets in the way of the first job, which is why the manufacturer's descaling and care advice matters.