If your NS1002 system appears to be calling for heat but the boiler is not responding, check the following:
• Ensure the Thermostat and Relay Module are both connected.
Confirm both devices are communicating with the system and showing as connected.
• Check the Relay CH light.
The CH light on the relay should flash green when the thermostat calls for heat.
• Listen for the relay clicking.
When the heating turns on or off, the relay should make an audible clicking sound.
• Possible valve, boiler, or wiring fault.
If the relay module is responding correctly but the boiler does not start, there may be a fault with the zone valve, boiler, or system wiring. Contact a qualified heating engineer.