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3. NORMAL OPERATION
Becoming familiar with how a tankless water heater normally
operates may help to troubleshoot it. Assuming it is properly
installed with appropriate gas, water, and electric
connections, the following is how it should operate:
1) ACTIVATION
a. A hot water tap is opened enough that the flow
sensor detects a flow rate through the heater greater
than the activation point of 0.5 gpm.
b. The fan activates after flow is detected.
c. The computer checks for any problems with the unit
before startup.
d. Igniter activates. You can hear the buzzing of the
spark igniter.
e. Main gas valve, proportional valve, and solenoid gas
valves will open. You will hear a deep "clunk clunk"
noise.
f.
Once a flame is detected, the red LED located on
the computer board will activate.
g. In a multi‐heater setup, the controller will
activate the next heater in 2‐4 gpm increments,
depending on the set temperature.
2) OPERATION
a. The proportional gas valve will modulate based on the amount of hot water demanded and the
temperature rise needed. The fan speed will modulate as well to create an efficient burn.
b. You will notice that only partial sections of the burner will be lit. This is normal operation; there
are three sections on the burner assembly, and the computer controls the amount of sections
needed based on the flow rate and temperature rise required.
3) SHUTDOWN
a. The heater will shut down when the water flow rate drops below the deactivation point of
0.4 gpm.
b. The heater will close the main gas valve and solenoid gas valves, extinguishing the flame.
c. When the flame disappears the red LED will turn off.
d. The fan will increase in speed to purge the venting of any remaining exhaust gases. The length
of post‐purge can last up to 1 ½ minutes.
e. The heater goes into standby waiting for the process to begin again.
Figure 2
*The purpose of this diagram is to illustrate tankless water
heater design concepts, and may not be accurate to the
unit's physical description.
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Troubleshooting Guide
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