Sangamo S255.3 24 Hour 4 Pin 3 On/Off Time Switch with Day Omit

The Sangamo S255.3 is a 24-hour electromechanical time switch with three independently programmable on/off cycles per day, rated at 20A switching capacity. The round dial face displays a numbered 24-hour clock with adjustable pins that set switching times, and a day omit dial that allows the unit to skip the 'on' operation on selected days without reprogramming.

Designed for commercial heating systems, industrial process control, lighting circuits and ventilation schedules, the S255.3 suits applications where repeating daily cycles need to be maintained across multiple zones or equipment. The 4-pin rear mounting pattern fits standard UK time switch housings and DIN rail adapters. The manual override button on the face allows temporary switching without disturbing the programmed schedule.

The electromechanical design runs on mains power with no battery reserve, meaning the clock stops during power cuts and requires resetting when power returns. The clear dial markings and physical pin mechanism make programming visible at a glance — each pin position corresponds to a 15-minute segment of the day. The 20A rating handles resistive and inductive loads including contactors, motorised valves, immersion heaters and commercial lighting circuits.

Product Specification Sheet

Product Manual

What happens during a power cut?

The S255.3 has no battery reserve. During a power outage the clock stops and will need to be reset to the correct time when power returns. The programmed pin positions remain in place, but the clock must be manually advanced to match the current time.

How are the on/off times set?

Each pin on the dial represents a 15-minute segment. Push pins inward at the times you want the switch to activate (on), and leave pins out at times you want it to deactivate (off). Up to three separate on/off cycles can be programmed per 24-hour period.

What does the day omit dial do?

The day omit dial allows the timer to skip the 'on' operation on specific days of the week without removing pins. This is useful for applications like heating systems that run Monday-Friday but stay off at weekends.

What is the 4-pin mounting pattern?

The rear of the unit has four fixing pins arranged in a round pattern, designed to slot into matching sockets on standard UK time switch housings or DIN rail mounting adapters. This allows the timer module to be removed for servicing without disturbing wiring.