Sangamo S254.3 Round Pattern 24 Hour 3 On/Off Time Switch - 20A 3 Pin

The Sangamo S254.3 is a round pattern 24-hour time switch with three programmable on/off cycles per day, rated at 20A for controlling heating, lighting or ventilation circuits. The mechanical dial allows three separate timed operations to be set across the 24-hour period, with on/off positions marked by movable pins around the circumference of the dial. A 3-pin plug-in connector on the rear allows the switch to be removed from its base for programming or replacement without disconnecting the circuit wiring.

Designed for commercial and residential applications including central heating zone controls, water heater scheduling and lighting timers, the S254.3 fits standard zone valve or pump control systems where multiple switching events are needed each day. The day omit dial on the front face allows the 'on' operation to be skipped on selected days without reprogramming the timer, useful for weekends or holidays when heating or lighting schedules change. The temporary override button forces the circuit on or off outside the programmed schedule without affecting the stored times.

The mechanical timer runs continuously on mains power with no battery reserve, so the clock advances in real time as long as the circuit remains energised. The clear polycarbonate cover protects the dial from dust and accidental adjustment once programmed. The 20A rating handles most domestic central heating pumps, motorised zone valves and immersion heater circuits directly, though loads above 16A should be confirmed against the system design to avoid nuisance tripping.

Product Specification Sheet

Product Manual

Does this time switch require a battery?

No. The S254.3 has no battery reserve. The mechanical timer runs continuously on mains power, so the clock advances in real time as long as the circuit remains energised. A power cut will stop the clock until power is restored, at which point the timer resumes but may need to be reset to the correct time of day.

What does the day omit dial do?

The day omit dial allows you to skip the scheduled 'on' operation on selected days without reprogramming the timer. This is useful for weekends or holidays when you want to prevent heating or lighting from switching on automatically, without losing your weekday schedule settings.

How is it wired into a heating system?

The S254.3 uses a 3-pin plug-in connector on the rear that mates with a separately-wired base unit. The base is hard-wired into the heating or lighting circuit, and the timer body plugs into it. This allows the timer to be removed for programming or replacement without touching the circuit wiring. Installation should be carried out by a qualified electrician in accordance with BS 7671 wiring regulations.

Can the manual override be locked off?

The temporary override button on the front allows manual on/off control outside the programmed schedule. There is no physical lock on this button, so it can be pressed by anyone with access to the timer. For applications requiring tamper-proof operation, the timer can be mounted in a locked enclosure.