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Electric Water Heater Wiring

By Dave Rongey - Summary:

How to Wire a 240 Volt Water Heater Circuit: Common Wiring Methods for an Electric Water Heater, Basic Water Heater Circuit Requirements, Connect Water Heater Wiring

Guide to Wiring an Electric Water Heater

Electrical Question: I’m wiring a electrical hot water tank.

  • I have a 50 Amp wire to it out of the box is a white red and black and copper ground.
  • Out of the hot water tank is only a red and black.
  • Where does the white wire from the house hook up to?

This electrical wiring question came from: Nate, a Homeowner from Whittaker, Michigan.

Dave’s Reply:
Thanks for your electrical question Nate.

How to Wire a 240 Volt Water Heater Circuit

water heater

Application: Wiring a 240 Volt Electric Water Heater.
Skill Level: Intermediate to Advanced, Best installed by a Licensed Electrical Contractor. Work in electrical panels is not recommended for homeowners, non-experienced individuals or non-electricians.
Tools Required: Basic Electricians Pouch Hand Tools, electric drill, auger bits and extension cord as needed depending on the scope of the project.
Estimated Time: Depends on personal level experience, ability to work with tools and install 240 volt electrical circuit wiring.
Precaution: Identify the main circuit of the panel, turn it OFF and Tag it with a Note before working with the wiring or installing the 240 volt wiring and circuit breaker.
Notice: Installing an additional 240 volt circuit should be done according to local and national electrical codes with a permit and be inspected.

Wiring an Electric Water Heater

  • Basic Water Heater Circuit Requirements

    • An conventional 240 volt electric water requires a dedicated circuit.
    • The the typical circuit is a 30 amp 240 volt dedicated circuit.
    • The circuit cable wiring includes two insulated wires designated as Line-1, Line-2 and the ground conductor.
  • Does a Water Heater Require a Neutral Wire?

    • At this time, the conventional hot water heater does not require a neutral, however that will most likely change.
    • Neutral wires are required for other 220volt and 240 volt appliances that have electronic controlsĀ  that require a dedicated neutral, which is included with the 4wire cord.
    • If the circuit wiring is supplied by a 4-wire cable, and there is a spare white wire then simply cap off the white wire with a wire connector fastened onto the end of the wire.
  • Connect Water Heater Wires

    • It is a very common practice to install a 10/2 Cable with a Ground Wire.
    • The 10/2 cable actually has 3 wires including the ground wire.
    • With this type of cable wiring method, the black and white wires are used for the 240 volt circuit, so the white wire is colored typically with either red or black electrical tape or a permanent marker.
    • A conventional electric water heater will come with a black wire and a red wire which are connected to the wires of the same color as described above. The ground wire is attached to the green ground screw which is in the same wiring junction box compartment which is built into the top of the water heater.
  • Protecting the Circuit from Overload Conditions

    • Never use a cable that is too small for the water heater circuit, and be sure the circuit breaker is sized correctly for the circuit. Typically with #10 gauge copper wire a 2-pole 30 amp 240 volt circuit breaker is installed.
    • If existing circuit wiring will be used for the water heater and the circuit is larger then the circuit breaker should be replaced with a 30 amp breaker. The rule of thumb is to size the circuit breaker for the smallest size wire type within the circuit, or as indicated on the equipment label or as instructed in the installation manual.

The Following links will assist you with 220VoltĀ  and 240Volt Water Heater Wiring
220 Volt Appliance Wiring Requirements
See how some 220 volt appliances do not use a white common wire, instead they use two hots and a ground.

Learn How to Wire it Right with my
Complete Guide to Home Electrical Wiring
Perfect for Homeowners, Students,
Handyman, Handywomen, and Electricians
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Wiring Home Electrical Circuits
120 Volt and 240 Volt Outlet Circuits
Wiring 3-Wire and 4-Wire Electric Range
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Troubleshooting and Repair Electrical Wiring
Wiring Methods for Upgrading Electrical Wiring
Electrical Codes for Home Electrical Wiring
....and much more.

» Click here to learn more about Home Electrical Wiring «
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10 Responses to “Electric Water Heater Wiring”
  1. Randy says:

    Why would an electric water heater have a 10-2 from a 30amp breaker to the heater, then have a separate 10-2 going from the heater out to the meter. This is a leased heater from the electric company and is in a apartment.

    • Dave Rongey says:

      Hi Randy,
      Since this is a leased water heater that is located inside an apartment it is possible that the additional 10-2 cable is being used to measure the electrical consumption of the unit at the meter location where a current transformer or other measuring device is installed.
      I hope this helps,

  2. Curtis Nelson says:

    I had an electric water heater and replaced it with a gas water heater. Years later I now am going back to an electric water heater. The previous two ten gauge 2 wire cables are still there. However one of the cables is now hooked up ( in the control panel box) to another 10 gauge cable with wire nuts, and connected with the white wire to white wire, and black wire to black wire, and leads out to my electric meter. Why are the wires connected this way, and what is this for? To make it a live wire again can I just link those wire nut connections to a proper 30 amp breaker?

    • Dave Rongey says:

      Hi Curtis,
      Application: Replacing a gas water heater with a 240 volt 30 amp hot water heater, and reconnecting to an existing 240 volt 30 amp hot water #10 gauge circuit.

      The original 240 volt 30 amp hot water #10 gauge circuit wires will need to be verified that they are not being used for some other purpose. Once this has been verified the white wires of the original circuit should be colored with red or black electrical tape to indicate that the white wire is not a neutral wire, but is instead being used for one power source of the 240 volt circuit.

      The water heater circuit wires both connect to a 2-pole 30 amp 240 volt circuit breaker for proper circuit overload protection. The ground wire is connected to the ground bar of the panel. All the circuit wires should be verified, identified and marked. This verification is essential from the panel location to the water heater location.

      I cannot speculate why the original circuit wires have been connected differently at the panel as you have described, and this is why circuit verification is very important, because if the circuit has been converted for a different application or purpose then the original circuit wires cannot be used, and further identification will be necessary.

      The typical circuit wire connections to the 240 volt water heater is black to black, the red wire of the water heater connects to the white wire which is colored with red or black electrical tape, and the ground wire is fastened and bonded to the ground screw of the water heater.

      I hope this helps,

  3. JoAnn says:

    Hi, I have replaced my 220 water heater. The wiring from the panel is 10 gauge, with three wires red, black and white. when I disconnected the old heater for removal, the white wire was connected to the ground screw. My question. I am installing a timer with a manual on and off switch. The diagram for the timer shows where to put the red, black and white wires and a place for the green ground. but I have no green/bare wire. Should I put the white wire on the ground in the timer and on the water tank? OR should the white wire go where the timer instructions show it should and put the white wire on the ground of the water heater? OR maybe just tape the white wire off at the heater?
    Thank you for your time. JoAnn

    • Dave Rongey says:

      Hi JoAnn,
      If the water heater timer requires a Neutral wire then one must be provided along with a separate ground wire. From what you have described the circuit does not have both of these wires. The solution would be to obtain a 220 volt water heater timer that does not require a separate neutral wire. The next important thing would be to have the white wire of the water heater circuit identified at the panel and verified or reconnected to be a ground wire, and marking the wire with green electrical tape at each end for proper identification.
      I hope this helps,

      • JoAnn says:

        Thank you Dave for your response. I went out to the panel and the white wire is in fact wired to the ground bar with all the other green or white wires coming from the panel. I made the decision not to use the timer at this time. I wired the water heater just like the old one was wired, with the white wire connected to the ground screw. All is good and we have hot water!
        Again thank you for your answer.

  4. chris sterup says:

    I have a hot water heater that I want to remove and replace the wiring with an outlet to utilize the dedicated circuit. Is this doable for someone who’s pretty handy, or do I need an electrician and how?

    • Dave Rongey says:

      Hi Chris,
      If you are referring to converting a 30 amp 220 volt circuit to be used as a 120 volt, then yes, this can be done fairly easy. Keep in mind that the circuit wiring will need to be converted to 120 volts at the electric panel, and a new circuit breaker must be installed and sized to the amperage of the receptacle that will be installed, which is typically 15 or 20 amps.
      Working in an electrical panel is not recommended for homeowners, so this is best performed by an electrician.

  5. raiford adams says:

    I have a Envi-ro-temp Energy Saver model 90a-1980 30 gal. single element 220 volt electric water heater and need to wire it in to my house.How do I wire it?


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