A pool pump timer interrupts the electric circuit powering the pump motor during off-use periods. Most pool pump timers are time-operated double-throw switches, meaning a timer controls a switch that connects to both wires entering and leaving the timer housing. The pump motor circulates pool water through the pool's filtration and chlorination systems. Usually an operator sets the timer so it turns on the pump motor for a short period of time several times throughout the day. Allowing the timer to automatically turn the pump on and off saves electricity without diminishing water quality.
Switch the pool pump's circuit breaker to the "Off" position. Usually this circuit breaker has a "Pool" tag and often connects to the "Main" electrical panel, found next to the electricity meter.
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Identify and locate the pool pump timer's wire terminals, using the timer's schematic as a guide. The schematic, located on the inside of the pool timer's lid, shows the wire terminal's positions, their functions and labels them. The wire terminals with the "Line" designation connect to the wires coming from the circuit breaker, and the wire terminals designated "Load" connect to the pool pump motor's wires.
Locate and loosen the timer's green screw with the proper screwdriver, often a 1/4- or 5/16-inch nut driver. The green screw, usually located next to the dial timer, grounds the timer.
Bend the bare copper wires from both wire sets around the interior perimeter of the timer box to the green screw, making sure they do not interfere or touch anything, then loop them around the screw. Tighten the screw.
Place one of the insulated line wires into the pump timer's "Line 1" terminal. Notice this wire's insulation color. Tighten the "Line 1" terminal with the proper screwdriver.
Place the load wire with the same color insulation as the wire entering the "Line 1" terminal into the pump timer's "Load 1" terminal. Tighten the "Load 1" terminal screw.
Place the second line wire into the pump timer's "Line 2" terminal. Tighten the "Line 2" terminal screw.
Place the second load wire into the pump timer's "Load 2" terminal. Tighten the "Load 2" terminal screw.
Many timers use this terminal pattern -- Ground, Line 1, Load 1, Line 2, Load 2.