Honeywell T3R Thermostat – Installation Guide
Important Disclaimer: The information below is for general guidance only and is based on the official Honeywell installation manual. All installation and wiring must be carried out by a qualified professional. Do not attempt installation unless you are suitably trained. Always switch off mains power before carrying out any electrical work.
1. Mounting the Relay Box
Choose a location near your boiler or heating system.
Securely mount the relay box using screws and wall plugs.
Leave at least 30cm clearance around the unit.
2. Wiring the Relay Box
Supports 24–230V on/off appliances including combi boilers, standard boilers, and 2-port zone valves.
- Use correct L, N, and switched live terminals.
- Strip multi-core cables to fit neatly into the block.
- Bundle single-core wires with a cable tie near the terminal block.
3. Pairing the Thermostat
The thermostat is pre-bound to the relay box. If re-binding is needed, follow the binding procedure in the manual.
4. Thermostat Positioning
- Mount on an internal wall, around 1.5m above the floor.
- Avoid heat sources, draughts, or direct sunlight.
5. Initial Setup Options
- Language selection
- Cycle rate (6 for gas boilers)
- Minimum on time (default 1 minute)
- Temperature limits
- 7-day or 5+2 scheduling
- Backlight, time format, daylight saving
Reminder: Installation should only be performed by a qualified heating engineer or electrician.