Description
This is a simple, mechanical 24‑hour time switch designed to sit over a standard single pattress (socket) box and give daily on/off scheduling in 15‑minute steps. The dial is a captive‑tappet style: you push individual tappets out to set timed periods and turn the dial to set the current time. It’s intended where someone wants straightforward, repeatable daily control — for example for pumps, heaters or other general purpose circuits that need to come on and off at the same times every day.
- Key specifications
- Model / reference: OP‑SBST
- Dial: 24‑hour with 15‑minute captive tappet intervals
- Load rating: 16 A resistive, 8 A inductive
- Contacts: volt‑free SPDT changeover
- Mounting: single pattress (surface or in‑wall pattress box)
How it works in practice
Operation is deliberately low‑tech. You set the dial to the current time and move the tappets that sit around the perimeter to create on periods. Each tappet represents a 15‑minute window, so shortest programmable period is 15 minutes. There’s a manual override with three positions — timed, off and constant on — so you can temporarily bypass the timetable without changing the tappets.
Where it’s useful
Because it’s a volt‑free SPDT mechanical timer it’s flexible: it can switch a live feed directly where the load is within its ratings, or it can operate a control circuit (for example to fire a contactor that handles larger loads). It’s well suited to domestic or light‑commercial uses where you want a repeatable daily schedule — typical uses include bathroom or circulation pumps, simple electric heaters, or lighting circuits that don’t need sub‑hour granularity. The captive tappet dial makes it easier to avoid accidentally dislodging settings compared with loose‑tappet timers.
Installation and compatibility
The unit is made to mount directly onto a single pattress box (surface or recessed). Electrical connections are by screw terminals with an earth park provided; the internal switch is volt‑free so you can use the device either to switch mains directly (up to its current rating) or to switch a lower‑power control circuit. It runs from the normal UK supply (220–240 V AC, 50 Hz) and consumes only around 1 VA itself.
Practical limits and things to check
Mind the load ratings: 16 A resistive is generous for many household circuits, but the inductive rating is lower (8 A at cos φ 0.6), so if you’re switching motors, transformers or other inductive loads you must check the inrush and running currents against that 8 A figure. The unit is not suitable for direct switching of discharge lighting without an additional contactor. Also bear in mind the minimum program increment is 15 minutes — this isn’t for applications that need short, precise pulses.
Build, reliability and user notes
The OP‑SBST is a straightforward, rugged mechanism rather than a feature‑packed electronic timer. Its synchronous motor gives a simple, reasonably accurate 24‑hour timing (typical mechanical synchronous accuracy is within a few seconds per day under normal supply conditions). The mechanical dial and captive tappets mean settings are easy to see and change; the manual warns not to rotate the dial anti‑clockwise when setting the time because the internal mechanism is designed for clockwise adjustment only.
The casing and size are compact so it integrates neatly into a pattress location rather than standing proud as a bulkier control box. For permanent installations you should follow the supplied wiring instructions and building‑regulation guidance — in most cases an electrician should carry out the final wiring and connection to fixed mains circuits.
Who this suits
Choose this timer if you want a low‑cost, reliable daily timer with clearly visible mechanical settings and the ability to switch moderate household loads or control a contactor for larger loads. It’s not for people who need smartphone control, sub‑15‑minute precision or to switch high inductive currents directly without an intermediate contactor.
Overall, the Optimum OP‑SBST is a practical, no‑frills solution where everyday, repeatable daily timing is the primary need — the kind of fitting often seen controlling pumps, simple heating circuits or timed lighting in domestic and light commercial settings.
