Projects
Installing an On-demand Water Heater
Project Overview
An on-demand water heater can easily be mounted under a kitchen sink or off to the side, in a place where looks don't matter. When you turn the hot water tap on, the flow turns on a heating element that heats the water as it runs through copper tubes. When the faucet goes off, so does the heat, saving you a lot of money in heating costs. If you are not experienced in working with electricity, hire an electrician or consult a book like The Home Depot's Wiring 1-2-3. To meet code, you will need an electrical shutoff switch within sight of the unit. Run armored cable or conduit (as shown). Make sure your breaker or fuse box has an extra circuit before starting. You'll need one free breaker for a 120-volt heater, or two free breakers for a 240-volt unit. Time needed to run wire or pipe is not included in the estimate.
4 Steps
Step 1
Run power for the unit
The heater will be either a 120-volt or a 240-volt circuit, and it must be a circuit wholly devoted to the heater. Either voltage requires 8-gauge wire, and the section exposed to the area under the sink must be armored cable or conduit. If the manufacturer's instructions call for installing larger cable or thicker wire, be sure you do so.
Step 2
If you're installing the heater under an existing sink
Turn off the water line. Drain the line by opening a faucet at a lower point somewhere in the house. Solder a cutoff valve onto the pipe stub that comes from the floor or wall. Solder a second valve onto what's left of the line that runs to the faucet, cutting the line as necessary to allow room for the heater.
Step 3
Screw the unit to the wall
Follow manufacturer's instructions. Connect the water supply line to the cold in-feed fitting by soldering copper pipe or via high-pressure flex connections, as shown here. Wrap Teflon tape around the threads. Hand-tighten then use a wrench. Connect the line going to the faucet to the hot water outlet using the same materials.
Step 4
Wire the unit
Follow the manufacturer's instructions on wiring exactly. Often, on a 240-volt circuit, the white wire connects to one of the hot terminals, and the black to the other hot terminal— they're often labeled L1 and L2. The ground wire will go to the grounding screw on the unit. On a 120-volt unit, splice the white supply wire to the white wire in the unit, and splice the black wire to the black. Cover with wire nuts and tape the nuts in place.
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