Installing an AC Water Heater Time Switch

In order to save on your utility bills and energy when using a water heater in your house, you need to install an AC (alternating current) water heater timer on the device. The system will enable you to set your own timer on the heater to only turn on when you require using hot water the most and setting it to turn off when it is not needed. Water heaters are designed to keep water in your tank hot even when you are not using it whereby the heater will turn on when the water cools down below your temperature setting. Whenever electricity runs for keeping the water hot inside your tank even during off-peak times, your electrical cost may increase.

What you need:

  1. Phillips or slotted screwdriver
  2. Hammer
  3. Stud finder
  4. Drill
  5. Wood screws
  6. 10/3 nonmetallic (NM) electrical whip
  7. Red wire connectors


  1. Firstly, you need to take your timer from its metal housing in order for you to install the housing on the wall nearby the heater. Then, you can use screws that help hold the timer into the housing.
  2. After that, you need to place a screwdriver against the 3/4-inch knockouts on each side of the metal housing. Then, you need to remove the knockouts by striking the screw driver with a hammer.
  3. Next, you need to slide a stud finder along the wall so that you would be able to locate a wall stud above the water heater, right between where the water heater power supply emerges from your wall and on top of your water heater. Then only you can start to mount the timer housing on the wall by using a drill and wood screws. After that, you need to reinstall your timer into the metal housing.
  4. Ensure that you turn the 30-amp double-pole breaker off to your electric water heater at your main breaker panel.
  5. After that, remove the screws in order to open an electrical access panel covering from the top of your heater. Then, pull the connected black, red, white and green wires out your water heater electrical access before you start to untwist the wire connectors from the four sets of wires.
  6. After that, you need to untwist the lock nut holding the electrical power supply cable into your water heater. The locknut threads must have connection with the connector inside the water heater and you must access it through the access panel.
  7. The next step is to wire the power supply on the timer housing. Next, you must attach 10/3 non-metallic electrical whip to the right knockout on the timer housing.
  8. After that, connect the green wire from the power supply cable and the green wire from the whip to the green ground and screwing them in a timer.
  9. Then, place the black wire from the power supply cable under the set screw labeled number 1. Then, place the black wire from the whip under set number 2 while the red wire needs to be placed onto the power supply cable.
  10. Next, thread the opposite end of the whip and its connector through the knout out opening on the top of water heater. Ensure that you secure the whip onto the water heater by using other heaters and with the other lock nut provided with the whip.
  11. Then, wire the next red wire from the whip to the red wire from the heater and also from a wire connector.
  12. Push the four sets of wires into the electrical access. Reattach the access panel cover to the water heater. Turn the 30-amp breaker on to your water heater at the breaker panel.

Image Credit:

Flickr CC

Additional Reading:

National Electrical Code Handbook (Mcgraw Hill’s National Electrical Code Handbook)

Green My Home!: 10 Steps to Lowering Energy Costs and Reducing Your Carbon Footprint