General Problems - A.O. Smith T-H2S-DV Troubleshooting Manual

5.2 TROUBLESHOOTING ‐ GENERAL PROBLEMS
Proceed to the Error Codes section if an error code is identified. For other common problems that do
not involve an error code, see if the following items help:
The water is not hot enough.
The water is too hot.
Temperature fluctuates when a fixture is opened.
Unit does not ignite when water goes through it.
It takes a long time to get hot water at the fixtures.
The fan motor is still spinning after operation has stopped.
Abnormal sounds come from the unit.
Loss of pressure at all sinks when the dishwasher fills.
Unit has power, gas, and water but does not turn on.
Multiple Heater Setup (Easy‐Link)
THE WATER IS NOT HOT ENOUGH
•
Compare the flow and temperature at the pressure relief valve.
o If the temperature and flow rate are correct at the PRV then the problem resides in the
plumbing line, not in the tankless unit.
•
Test the hot water temperature with a handheld thermometer to measure how far off the water
temperature is from the set temperature.
o The set temperature may be set too low. The temperature can be changed with the
pushbuttons on the PCB or by the remote temperature controller, if one is installed.
•
Check for cross plumbing between cold water lines and hot water lines. See the Procedures
section (p. 24) for instructions.
•
Unit may be hard water scaled. The scale acts as an insulator preventing the heat exchanger
from transferring heat to the water. Contact a service agent.
•
The unit may not be receiving enough gas.
o The gas supply valve may not be fully open.
o The gas line may be sized improperly.
o The gas supply pressure may be too low. This may be caused by a malfunctioning gas
supply regulator, so check to see if your regulator is working properly.
•
Check to see that a check valve is installed between the pump discharge and the connection to
the cold water supply. Inspect the check valve for proper operation. If there isn't one installed,
or if it is malfunctioning, cold water may be back‐feeding into the system.
•
Double‐check for a 101 error code. A 101 error code will reduce the amount of gas input into
the heater.
•
Output temperature will be affected if air flow is impeded.
o Check construction dust and debris in venting, such as dry wall.
o If there is dust inside the cabinet, there will also be dust inside the burner and heat
exchanger. See the procedure for cleaning the burner (p. 28).
THE WATER IS TOO HOT
•
The set temperature may be set too high. The temperature can be changed with the
pushbuttons on the PCB or by the remote temperature controller, if one is installed.
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Troubleshooting Guide