Heat HubR LED or app reports H01; heating relay does not respond to thermostat calls for heat.

Safety: The Heat HubR is a mains-powered device. Isolate power at the fused spur or consumer unit before removing the cover or touching any wiring. If you are not competent with mains wiring, use a qualified electrician or heating engineer.

• Check app status: Confirm that the Wiser app is actually calling for heat (room temperature below setpoint and schedule active).
• Verify wiring: With power isolated, remove the Heat HubR front cover and check that the boiler's call-for-heat wires are correctly connected to the designated heating relay terminals (e.g. COM and NO). Tighten any loose terminal screws.
• Listen for relay click: Restore power and, while calling for heat from the app, listen for a distinct click from the Heat HubR. No click suggests a failed relay or control circuit.
• Check boiler response: If the relay clicks and you measure voltage switching correctly at the relay output (qualified person only), but the boiler does not fire, the issue may be with the boiler or external controls rather than the Heat HubR.

If H01 persists and the relay does not operate, the Heat HubR PCB or relay is faulty. Replace the Heat HubR or have the relay replaced by a qualified electronics technician.