Tankless Water Heaters - Troubleshooting & Service Guide





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PRE-SERVICE TROUBLESHOOTING CHECKLIST

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Verify the heater is properly mounted vertical on the wall or structure with the inlet and outlet fittings of the heater on the top, pointed toward the ceiling or upwards.
Verify water flow through the heater. Make sure that any shut off valves to the heater (on the cold water inlet side) are in the open position to allow water to fill the heater.
Verify that the heater is plumbed properly. The cold water pipe should be connected to the right inlet fitting and the hot water pipe connected to the left outlet fitting.
Check the plumbing connections thoroughly and the heater for any signs of leaks.
Verify a high flow rate fixture by using a 1 gallon bucket and watch. Determine if the flow rate matches the specifications of the Tankless model selected for the application.
With the POWER TURNED OFF (must be confirmed with a volt meter), check for any loose or disconnected control wires to the control panel or to the individual components of the heater. Also, verify the power wires connected to the control board lugs are tight. If stranded wire is used, check that all strands are in the lug. Any strands outside the lug may cause electrical shorts on the board with other components.
Verify all appropriate circuit breakers are turned on and functioning properly.
With the POWER TURNED ON, verify that there is power in all circuits connected to the heater. Check the power lugs on the control board to make sure there is 208 to 240 volts, AC across the lugs labeled L1 & L2 for each circuit.
Check for any diagnostic codes. There may be more than one code. Refer to the Diagnostic Codes for interpretation of the diagnostic code(s).
Check for a tripped high limit switch located at the top of the heating chamber. To identify, follow the brown wires from the control board to the switch. Turn off the power to the heater before resetting the switch. Note: Newer four chamber heaters will have an auto reset limit switch. Generally, this will be the 160 degree F switch located on the top right of the heater. The left limit switch has a manual reset.
At the control panel, check the position of the thermostat knob setting. It may need to be adjusted to achieve the desired temperature. The normal setting is about 3 o’clock position (should provide about 120 degrees F). Turn clockwise to increase temperature, counterclockwise to lower the temperature.
Check for malfunctioning faucets or incorrectly adjusted tempering, mixing or pressure sensitive valves downstream from the heater. This can be checked by feeling the outlet pipe on the left of the heater while the water is running. If it feels hot but the water at the faucet is cold, then check the plumbing at the faucets for possible adjustments or reversed lines.
Check for the possibility of cold water lines that might be accidentally connected to the hot water lines downstream from the heater.
Check for a non-functioning temperature sensor or heating element. See the following Component Testing and Trouble Shooting Tables for detailed procedures.