Horstmann / Products / Heating and hot water controls / Timeswitches & programmers / 425 series

Heating and hot water controls

Timeswitches & programmers

425 Series


With rotating 24 hour dial, on and off tappets and slider switches for setting the programme, the 425 series are considered to be one of the simplest programmers to use and understand particularly where householders are used to and prefer a mechanical device.

The range consists of three models, the Coronet single circuit timeswitch and the Tiara and Diadem two circuit programmers. The Diadem has indicator lights and the Tiara does not (for use with fully pumped systems).

  • Applications
  • Features and Benefits
    • Control of most domestic gas or oil-fired central heating and hot water systems.
    • Combination ('combi') boiler systems
    • Stored hot water systems
    • Solid-fuel systems
    • Additional zone control
    • Simple to use with easily understood settings adjustable in seconds
      • All control elements are visually accessible
      • Fewer call backs 
    • Advance control to allow manual override switching ON or OFF
      • Allows the user to switch the heating off or on early without disturbing any existing settings 
    • 2 On / Off settings per 24 hours
      • Convenient morning and evening settings 
    • Choice of programme settings
      • Allows the user to pre set a choice of programmes 
    • Easy to install, uses a 9 pin standard backplate
      • Backward compatible with all previous 425 ranges 
    • Voltage free contacts
      • Coronet is suitable for use with combi boilers 
    • Diadem and Tiara 6 Amp rated, Coronet 13 Amp rated
      • Diadem and Tiara suitable for most types of wet domestic central heating
      • Coronet can be used for loads up to 3kW as well as conventional heating


    Single Circuit

    Twin Circuit

    Perm ON/


    ON All Day


    OFF twice

    a day

    Combi boiler

    Pumped Systems

    Independent CH / HW Programme

    Immersion Heaters

    Indicator Lights

    425 Diadem




    425 Tiara





    425 Coronet