Helpful video reference. We use GSH Electrical's "Fault Finding - Storage Heater NOT Getting HOT" as the video reference here. The presenter works through a live site visit on a heater that won't heat up, testing elements with a multimeter and checking each component in turn. The approach is methodical and accurate to UK practice.
1. Check the consumer unit first
Storage heaters in the UK run on a dedicated Economy 7 overnight circuit, separate from the main ring final. Look for a second MCB row or a separate consumer unit, often labelled "E7", "off-peak" or "night" and fed through a separate meter or time switch.
If the MCB is tripped, try resetting it once. If it trips again immediately, something on that circuit is drawing too much current or has a fault to earth. Note that down and move on to checking the heater itself.
2. Check the FCU fuse
Most storage heaters are fed via a fused connection unit on the wall, rated at 13 A or 20 A. Pull the fuse carrier out of the FCU body. Set your multimeter to continuity or resistance and touch one probe to each end of the cartridge fuse. You should hear a beep or see a resistance close to zero. If the fuse reads open-circuit, replace it with the correct rating marked on the FCU.
A blown fuse often points to a failed element drawing a short-circuit current at the moment it went. Replace the fuse and test the heater: if the fuse blows again, the element is almost certainly the cause.
3. Check the charge and output controls
Night storage heaters have two separate controls that are easy to confuse. The input (or charge) control is usually a numbered dial on the back or side of the unit. It tells the heater's internal thermostat how much heat to store overnight: zero means it will not charge at all. The output control, which may be a rotary dial, a sliding lever or an automatic damper, governs how quickly the stored heat is released during the day.
Both controls set to their minimum is the most common non-electrical fault found on site. Turn the input dial up before Economy 7 hours begin and check again the following morning.
4. Isolate the heater safely
Switch off the overnight circuit MCB at the consumer unit. Pull the FCU fuse carrier if one is fitted. Then use a voltage tester to confirm there is no voltage at the flex entry or the element terminals inside the heater. Only then remove the front or top panel.
5. Test the heating elements
Most night storage heaters contain between two and four elements: a main charging bank that stores heat in the firebricks, and sometimes a smaller boost or direct-acting element for immediate warmth.
With the heater fully isolated, locate the element terminal block. Set your multimeter to resistance. Place one probe on each terminal of the first element pair. A healthy element reads somewhere between 15 and 100 ohms, depending on its wattage rating: a 500 W element at 240 V should read around 115 ohms, a 1 kW element around 58 ohms, and a 2 kW element around 29 ohms. An open-circuit reading (OL or infinite) means the element filament has broken and the element needs replacing.
6. Inspect the input thermostat
The input thermostat sits against the brick stack inside the heater and cuts charging once the bricks reach the set temperature. If it has failed open-circuit, the heater will never charge because it permanently signals "full". If it has failed closed-circuit, it will charge without limit, which can cause overheating and trips.
With the heater cold and fully isolated, the thermostat should read near-zero ohms (closed contact). An open reading on a cold heater means the thermostat has failed open and needs replacing.
When to call us
A failed element or fuse is often a job a careful homeowner can manage. But if the circuit keeps tripping, if the wiring is old, or if you are finding mixed cable types, call. Storage heater circuits can be on older wiring that has not been touched since the Economy 7 tariff was introduced, and it is worth having an electrician check the whole circuit while you have them on site.
Storage heater fault on a rental property?
Richard can carry out a fault-finding visit on any Economy 7 or storage heating circuit in east Kent. Small local jobs in Sandwich are £10 per 10 minutes.
Contact Richard