Hot water thermostat and fused spur replacement at a Clapham venue.

The brief

Existing customer in SW4 Clapham reported the hot water cylinder no longer regulating: water arriving cold at the taps despite the cylinder showing as energised. Return visit with parts to replace the thermostat and review the supply.

On site

Attended with required parts, liaised with the manager at head office, collected keys to access the premises.

Safe isolation

Isolated the electrical supply to the affected unit at the consumer unit. Carried out safe isolation procedures per BS 7671 (locked off, tested, retested) before removing any cover or making any electrical connection live or dead.

Fused spur replacement

Stripped out the faulty fused spurs feeding the hot water cylinder circuit. Identified the existing power supply cabling as undersized for the load the cylinder draws: the cable rating was below the manufacturer-spec current for the heater element, which had been a contributing factor to the fused spur degradation.

Upgraded the cabling to meet current load requirements and BS 7671 safety standards. New fused spurs supplied and fitted, correctly rated for the cylinder draw.

Thermostat replacement

Supplied and fitted a new thermostat to the hot water cylinder. Connected per manufacturer wiring diagram. Reinstated power to the circuit.

Test

Carried out full testing of the system: insulation resistance, earth continuity, polarity per BS 7671. Verified thermostat regulating correctly across its operating range by monitoring water temperature pull-up under load.

All components now operating correctly and safely. Test results recorded and certificate issued.

Outcome

• Hot water cylinder regulating correctly. Customer back to normal operation.
• Undersized cabling upgraded to current BS 7671 standard.
• New fused spurs and thermostat fitted, certified.
• Electrical installation certificate issued for the work.

Cost band

Return visit including thermostat replacement, fused spur swap and cabling upgrade typically £280-£480 + VAT depending on cable run length and certificate scope. Parts charged at trade rates.