HTT4 is a tamper-proof mains-powered thermostat with a built in 230-volt relay, capable of either normal or volt-free switching. It is ideal for use in public areas, and in places where temperature adjustment after installation is not required or desired. HTT4 is ideal for use in most types of heating systems that respond to a 230-volt mains electrical on/off signal. The temperature set-point is adjusted via an internal dial that can only be accessed when the main cover is removed.

Attractively styled, HTT4 outperforms many older types of thermostats and can often produce energy savings of 10% compared with traditional technologies.

The temperature control accuracy of ±0.5 °C and range of load compensation settings, for gas, oil and electrical systems, reduce the temperature swing that normally occurs with older style thermostats. Consequently HTT4 helps save energy, as the control algorithm allows the boiler to operate in condensing mode for longer periods.



  • Multi-occupancy buildings

    In buildings with many people coming and going, it is often desirable to set a comfortable temperature that cannot be changed by unauthorised persons. HTT4 is ideal in this situation, because the temperature setting dial is on the back of the device and can only be accessed when the thermostat has been removed from the wall, using a screwdriver.

    Control of most mains-operated heating systems

    HTT4 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 load compensation software, which optimises the switching of the boiler to maximise its efficiency.

    Zone Control

    HTT4 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

    HTT4 is great for new systems, because the combination of load compensation 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

    HTT4 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 load compensation software and added accuracy of electronic temperature sensing can be enjoyed, with minimal cost and effort.

  • Key Feature

    • Tamper-resistant internal temperature setting
    • Sophisticated load compensation software
      • Improves economy
      • Tight and accurate control while minimising temperature overshoot
    • 230 volt mains operation
      • No batteries required
      • Can connect to existing thermostat  wiring
    • 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