No hot water at taps, Gledhill thermal store or unvented cylinder appears powered but water remains cold

Safety: Isolate electrical power and, if working on boiler circuits, ensure gas safety regulations are observed. Gas boiler internals must only be serviced by a qualified engineer.

Steps:

• Check controls: Ensure any programmer or timer is set to provide hot water and that room/cylinder thermostats are calling for heat.
• Boiler check: Observe whether the boiler fires when hot water is demanded. If not, the issue may be with the boiler, its controls, or the call‑for‑heat wiring from the Gledhill unit.
• Immersion test: If your Gledhill unit has an immersion backup, switch to immersion mode (if provided) and see if the cylinder heats. If it does, the primary/boiler side is at fault; if not, test the immersion element and thermostat as described in earlier entries.
• Motorised valve: On systems with a separate primary circuit, check that the 2‑port or 3‑port valve feeding the cylinder opens when there is a demand. A stuck valve will prevent heat transfer.
• Thermostat: Verify that the cylinder thermostat is set correctly (typically 60°C) and has not failed open‑circuit.

When to call a pro: If the boiler does not respond to a clear call for heat from the cylinder, or if gas components are involved, contact a qualified heating engineer.