A range of purpose-designed room thermostats that offer the latest energy saving control technology, combined with our established design and manufacturing expertise.

HRT4-A is a mains-powered thermostat, with a built in 230 volt relay, capable of either normal or volt-free switching. This makes it ideal for use in most types of heating system that respond to a 230 volt mains electrical on/off signal.

Aesthetically pleasing, HRT4A outperforms many older types of thermostat and can often produce energy savings of 10% compared with traditional technologies.

The temperature control accuracy of ±0.5 °C and range of TPI settings, for gas, oil and electrical systems, reduce the temperature swing that normally occurs with older style thermostats. Consequently HRT4-A helps save energy, as the control algorithm allows the boiler to operate in condensing mode for longer periods.



  • Control of most mains-operated heating systems

    HRT4-A is perfect for controlling most mains-operated domestic gas or oil-fired central heating and hot water systems. It can save around 10% in energy costs through use of the integrated TPI software, which optimises the switching of the boiler to maximise its efficiency.

    Zone control

    HRT4-A is small, low cost and discrete. This makes it suitable for individual zone control, such as setting upstairs and downstairs temperatures independently in a two-zone heating system.

    New systems

    HRT4-A is great for new systems, because the combination of integrated TPI software, mains power and built-in relay means the heating system can be made operational with minimal complexity, while delivering excellent heating comfort and efficiency.

    Replacement of conventional room thermostats

    HRT4-A fits on to the industry standard 6-pin wall plate, so it can be fitted as a drop-in replacement for most existing thermostats.  The benefits of TPI and added accuracy of electronic temperature sensing can be enjoyed, with minimal cost and effort.

  • Key Feature

    • Suitable for use in most heating systems controlled by a 230 volt on/off signal
    • Mains operation
      • No batteries required
      • Can connect to existing thermostat  wiring
    • Sophisticated time proportional integral (TPI) algorithm
      • Improves energy efficiency
      • Consistent and accurate control, while minimising temperature overshoot
    • Specification
    • Electrical

      Contact rating

      3 (1) A, 230 V AC

      Contact type



      3 V DC (2 x AAA alkaline batteries)


      Set temperature

      +5 °C to +30 °C+5 °C to +30 °C

      Temperature accuracy

      ±0.5 °C (at 21 °C, with 0.5 A load)


      Dimensions (W x H x D)

      86 mm x 86 mm x 36 mm


      0.2 kg (approx.)

      Case material

      Flame-retardant thermoplastic


      Industry standard 6-pin wall plate


      Enclosure protection


      Pollution degree


      Insulation class

      Double insulated

      Operating temperature range

      0 °C to +40 °C


      Design standards

      EN 60730-2-9