Take control of your hardware with relays. Solid State relays are recommended for high amperage applications such as elements where as SPDT are recommended for low amp projects such as pumps and valves. A solid state relay will have a common trait known as leak current. This current is nominal but can have a negative impact with low amperage projects; for example, the leak current can cause your gas valve to hang open after the intended time frame. An SPDT relay is similar to a contactor in that it makes a physical connection, and as such you will here a coil click when you send it the signal. The SPDT relays require a 12 volt power supply in order to operate, but one 15w supply is good for up to 8 relays.