Water Heater Wiring, How to Wire a New Water Heater, or Replacement Water Heater, and How to Make the Wiring Connections, Hook up the wires, and check the heating elements. Also describes the electrical circuit wiring for a 240volt 30amp water heater. DIY Electrical Wiring from an Electrician. Complete with easy to understand wiring example, and an easy to follow process which is explained by a licensed electrical contractor.