Relays Contactors and Timers

Relays, contactors and timers form the control backbone of a properly automated grow room. HPS ballasts and high-wattage electrical equipment require heavy-duty contactors to switch safely — standard domestic timers cannot reliably handle the inrush current of multiple 600W or 1000W HID ballasts firing simultaneously. Correct timer and contactor selection protects your equipment, prevents electrical faults, and ensures your photoperiod plants receive perfectly consistent light cycles.
Contactors for HID Lighting
A contactor is an electrically operated heavy-duty switch designed to handle the high inrush current produced when HID ballasts switch on. Standard 13A domestic timers can weld closed or fail prematurely under this load — potentially leaving lights permanently on or off at a critical point in your grow cycle. A properly rated contactor (typically 25A, 40A or 63A depending on the number of ballasts) switches the high current safely while being controlled by a standard 5A signal from a basic timer.
Use a contactor for any setup running more than two 600W HPS or HID ballasts, or for any single ballast operating above 1000W. The contactor is wired between your mains supply and the ballasts, with a simple timer controlling the contactor coil circuit. This two-stage switching arrangement is the professional standard in commercial growing operations.
Analogue and Digital Timers
15-minute interval analogue plug timers are the simplest and most reliable option for light cycling. Digital timers offer programming down to 1-minute intervals and multiple on/off settings — useful for complex irrigation schedules or multi-stage lighting programmes. For grow rooms running multiple devices on different schedules, a multi-outlet digital timer panel simplifies wiring and programming significantly.
We have been supplying timers and contactors to UK growers since 2017. Browse our full range below.