Here's how Scott Bennett does it, for the Bennett Racing…
Airotronics new TH3X series solid state timers deliver reliable performance in high power applications, with a heat sink that spans the entire base of the unit.
TH3X 10 amp timers are available with various timing modes and offer four time setting options: adjustable via integral or external pot, factory fixed internal, or fixed via external resistor.
Set variable time periods from 0.1 second up to 1000 seconds, for any range up to 24 hours. Specify fixed time periods in full seconds or hours. Input voltage ranges 24VAC, 120VAC, 240VAC.
Timers and Timing modes
TH3XKA Repeat Cycle On/Off
TH3XL Interval On Delay
TH3XM Delay On Break (Dry Initiate)
TH3XML Delay On Break (Hot Initiate)
TH3XP Single Shot on Make (Dry Initiate)
TH3XPL Single Shot on Make (Hot Initiate)
Choose TH3X timers for situations requiring 10 Amp continuous current handling and up to 60 Amp AC single-cycle surge handling. These timers are totally encapsulated for protection from harsh environments and receive 100% operational testing before shipping.