Many plants require a certain light-cycle (often 12/12) in order to begin flowering or fruiting. In order to switch a high power hydroponic indoor HPS grow-light on and off automatically usually requires a combination of a mains time-switch and a relay or contactor. A standard time-switch used on its own for this purpose will usually arc-out and die very quickly. All our relays, contactors and timeswitches are from quality manufacturers and will give you peace of mind when it comes to reliably and safely switching your grow-lights on and off at the correct times.