We used an Insteon system (No. 2477sa1 relay, and No. 2245-222 hub) in this application, but there are many other brands available. If you’re comfortable working with electricity, you can install the unit in a few hours. You’ll need a 4-in. square metal utility box, black 10-gauge THHN wire, a square cover, armored flex conduit, flex connectors, and a hacksaw or a reciprocating saw with a metal-cutting blade.
Mount the relay and electrical utility box on the wall near the water heater. Then disconnect the flex conduit from the water heater and install it in one of the knockouts on the new electrical box (Photo 1).
Then cut a length of flex conduit to run from the electrical box to the water heater (Photo 2). Secure the flex conduit to the wall and water heater using 1-in. straps and screws.
Shove two lengths of 10-gauge black THHN wire and one bare copper wire into the flex conduit running between the electrical box and water heater. Connect the bare copper wire from the main panel to the green bonding screw in the electrical box. Then connect the bare copper wire from the water heater to the remaining portion of the copper wire using a wire nut (Figure A). Next, connect the “line” wires from the Wi-Fi relay to the feed wires coming from the main panel. Connect the “load” wires from the Wi-Fi relay to the wires coming from the water heater.
Power up the water heater and connect the Wi-Fi hub to your router. Download the app for your phone and configure and test the relay.
Figure A: Connect the wires
Secure the bare copper wire from the fuse box to a green grounding screw in the electrical box, leaving at least 6 in. for a pigtail. Connect the “line” wires from the relay to the feed wires from the fuse box using wire nuts. Connect the “load” wires from the relay to the wires going to the water heater and secure with wire nuts. Then connect the bare copper wire from the water heater to the bare copper pigtail using a wire nut. Fold all the wires neatly into the electrical box and install the cover. Connect the wires at the water heater.