How should I check what's wrong with my Immersion Heater?
Fact checked by members of our engineering and technical team.
The following article will explain to you how to check for faults or issues with your Immersion Heater. For additional information on how to change the immersion heater, please read our step-by-step element replacement.
There is no electricity supply to the Immersion Heater
Check if an electrical current is reaching the heater - the circuit breaker may have tripped. For full wiring and RCD guidance, see our installation and wiring guide.
The over temperature trip in your Immersion Heater’s thermostat has cut out
There should be a small button on the thermostat which may have tripped. Push this back in place to reset the cut out.
The thermostat in your Immersion Heater is faulty
Carry out a resistance check across the element terminals. If the resistances are correct, the issue is likely thermostat-related - see our immersion heater thermostats and controls.
The Immersion Heater has failed to earth
Insulation breakdown is a common fault causing current to flow from live to earth. In hard-water or corrosive conditions, an Incoloy Thermtec element is more resistant to the deposits that cause this. This can create the following problems:
- RCD will trip if its on a protected power feed
- Current flow is often increased, which can blow fuses, MCB tripping or burnt accessories
- A tripping MCB may prevent it starting. This fault can be detected by measuring resistance between the element connections and its casing. This should be less than 1 ohm
The Immersion Heater has gone open circuit
Perform a resistance test across terminals. If resistance is infinite, the unit has gone open circuit, and the Immersion Heater will need to be replaced - browse our domestic immersion heater range or our industrial immersion heaters for the right replacement.
Still unsure?
Our immersion heater FAQ covers identifying the right replacement, and our technical team can help with bespoke or commercial systems.