BoilerFaultCodesGrant Demand Fault Code
Also written as DEMAND — same fault.
The Grant Demand fault code means: your boiler is not currently receiving a signal from your timer or thermostat telling it to switch on.. It appears on 3 Grant models in our database.
Technical description: If not lit this indicates either timer or programmer is not calling for hot water / switch is not set to constant
What causes the Grant Demand fault?
This occurs when there is a break in communication between your heating controls and the boiler. The most common reason is that your room thermostat or timer hasn't been set high enough to trigger a heat request, but it can also be caused by flat batteries in a wireless controller or a faulty receiver box failing to pass the signal through.
This issue is frequently noticed during the first cold spell of autumn when homeowners try to switch their heating on for the first time after the summer break.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperature.Ensure your programmer or timer is set to 'ON' or 'AUTO'.Check if the batteries in your wireless thermostat need replacing.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Grant models that show the Demand fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Grant Demand fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026