How to Diagnose a Faulty Immersion Heater Element
Fault-Finding and Safety Procedures
This document provides technical guidance on diagnosing faults with hot water immersion heater elements and thermostats using a multi-meter. Before beginning any diagnostic work, it is mandatory to perform a full safe isolation procedure to ensure the components are electrically safe to handle. This involves proving the circuit is dead and securing it against accidental re-energisation.
Testing an Immersion Heater Element
To test an immersion heater element for faults, first, remove any cover and the thermostat to access the live and neutral connection poles for the heating element.
Set your multi-meter to the resistance setting, measured in ohms (Ω). Connect the multi-meter probes between the live and neutral terminals of the element. For a typical 3kW immersion heater, you should expect a resistance reading of around 15-25 ohms. An open circuit or OL reading indicates a failed element.
Testing an Immersion Heater Thermostat
To test the immersion heater thermostat, turn the thermostat dial to its maximum heat setting. This action simulates a demand for heat from the hot water cylinder, which should cause the internal switch to close, completing the electrical circuit.
Using a multi-meter set to resistance (ohms), test for continuity across the thermostat’s switch terminals. A low resistance reading confirms a closed circuit, indicating the thermostat is functioning correctly. An ‘Open Line’ (OL) or infinite resistance reading signifies a faulty thermostat. Many immersion heater thermostats are replaceable as a separate component from the main heating element.
Customer Advice for Immersion Heater Replacement
If the immersion heater element is found to be faulty and requires replacement, it is crucial to understand about the potential complications. The process of removing an old, corroded immersion heater carries a risk of damaging the hot water tank or cylinder, which could lead to a leak or the need for a complete cylinder replacement.
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