Electric Water Heater Wiring: A Comprehensive Guide
Understanding Electrical Requirements
Replacing an electric water heater involves specific electrical requirements to ensure safety and compliance with local codes. This guide focuses on the electrical aspects of installing a standard tank-style electric water heater.
Locating Electrical Connections
The electrical connections for a water heater are located in a built-in junction box on top of the tank. This box is enclosed by a cover plate that can be removed for inspection. Typically, the wire conductors are enclosed in flexible conduit or metal-clad (MC) cable for flexibility.
Testing for Power
Before touching any electrical connections, turn off the power to the water heater circuit at the breaker box. Use a non-contact voltage tester to confirm that the circuit is indeed off by testing at the water heater.
240-Volt Dedicated Circuit
Electric water heaters require a 240-volt dedicated circuit, which means it serves only the water heater and no other appliances or devices. The circuit wiring typically includes a 30-amp double-pole breaker and 10-2 non-metallic (NM) or MC cable.
Wire Connections
- Black circuit wire: Connects to the black wire lead on the water heater.
- White circuit wire: Connects to the red or white wire lead on the water heater.
- White circuit wire: Wrap with black or red electrical tape at both ends (water heater and breaker box) to indicate it is a “hot” wire, not a neutral wire.
- Circuit ground wire: Connects to the green ground screw on the water heater or its ground lead.
Heating Element Wiring
Electric water heaters have inner wiring that runs from the junction box to two heating elements, each controlled by a thermostat. These components are located inside access panels on the side of the tank.
The Bonding Question
Some local building authorities may require a bonding wire, or bonding jumper, between the hot and cold water pipes serving the water heater. This jumper is not required by the National Electrical Code or Uniform Plumbing Code, but it may be necessary to ensure a reliable bond in a metal water piping system. It may also help reduce corrosion and maintain the electrical grounding pathway.
Bonding Wire Requirements
- 6 AWG bare copper wire
- Ground clamps on each hot and cold water pipe
- Smooth part of the pipe, away from fittings
Additional Tips
- Ensure the jumper connections are in place after installing a new water heater.
- If replacing a thermostat or heating element, you may encounter wire leads connected to screw terminals.
- Always consult with a licensed electrician for any electrical work to ensure safety and compliance.