Emergency Boiler Repair in Belvedere (DA17)

The 2021 Census counts 1,168 households in DA17 with electric-only central heating, 15.6% of the district, the highest share of the 18 and well above the 8.7% for England. Its option read "Electric (including storage heaters)", so the figure does not split storage heaters from electric boilers. This page is about the boiler: a box on the wall with no flue, no gas pipe and nothing to relight, heating water that a pump sends round radiators. About a third of households, 32.6%, live in purpose-built flats, and needing no flue is one reason electric boilers turn up in them.

Nothing burns in one, but plenty can trip.

Electric boilers on wet radiators

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Inside the case there is no burner and no flame. Heatrae Sadia’s Amptec manual describes the water being heated as it passes over electric immersion elements in a chamber, and something has to switch those elements on and off to hold the temperature: a contactor on EHC’s Slimjim, solid-state switching on the Amptec, triac boards on Strom’s boilers. Round that sit the protections, and each one is a way for the heating to stop. A thermal cut-out cuts the power if the water reaches about 100°C, and on the Slimjim and Fusion Comet a tripped one leaves the front panel dark, which looks like a lost supply. On the Slimjim, EHC says a service engineer has to reset it and then find out why it went. A flow or water sensor keeps the elements off when water is not moving through the boiler, or not there at all, so air in the system, a pump that has stopped or valves left shut will stop the heat, and the Fusion Comet flashes its pump light to say so. EHC’s fault table for the Fusion Comet traces a boiler that runs but only partly heats to one or more elements getting no voltage from the power board. And in a home with an electric shower, EHC recommends a shower sensor and Heatrae Sadia describes a relay, each of which switches the boiler off while the shower runs, so heating that stops while someone showers and comes back afterwards is doing what it was wired to do.

That is why this is only partly a plumber’s job. An electric boiler runs on a heavy circuit of its own: EHC’s table for the 9kW Fusion Comet gives a load current of 37.5 amps on 50 amp protection, and for the 14.4kW model 60 amps on 80. EHC calls for a 30mA double-pole RCD, an isolator beside the boiler when it is not by the meter, and cable sized by calculation to BS 7671. Strom adds that its boilers draw more current as the voltage rises, and can leak current to earth by design, so an RCD that keeps tripping may mean the boiler needs one of its own.

Heatrae Sadia says plainly: loose connections will cause a fire.

What you can check is all on the outside. Is the display lit, and is it showing a code or a flashing light? Is the boiler’s breaker at the board on, and the isolator beside the boiler? Is the programmer or room thermostat asking for heat? Is anyone using the electric shower? If a breaker has tripped, putting it back once is reasonable. If it goes again, leave it off: Electrical Safety First says an RCD that keeps tripping likely means a fault in an appliance or the wiring, and Strom lists loose connections and the wrong cable or breaker among the causes of nuisance tripping on its boilers.

Leave the casing on: Strom’s cut-out resets are inside it.

We test both halves. On the electrical side that means the supply at the boiler’s terminals, every connection, the switching and each element: the Amptec manual gives an element’s resistance as about 19 ohms on most models and its insulation to the case as more than 2 megohms. On the water side it means flow, air, the pump, and any sign of water getting into the case, which Heatrae Sadia, EHC and Strom all warn about. Being plumbers and electricians, we can follow a fault across that line without handing it on. Then it depends on the model. A dead power board or sensor on the Fusion Comet is a replacement part, but Heatrae Sadia says an Amptec whose elements test open circuit, or short to the case, must be replaced.

If the elements on yours have gone that way, we also arrange boiler installations, and the first question then is what the supply and the home can take.