Ruud PowerVent AP14236 - Manual (Page 26)

26
Sequence of Operation…
During initial start-up or a call for heat,
the control will verify the vacuum switch
is open.
Once the control verifies the blower
vacuum switch is open, the control
will energize the blower motor for the
pre-purge sequence (approximately 5
seconds).
The control will verify the blower vacuum
switch has closed, ensuring that the
blower is functioning properly and that the
venting system is not blocked.
The control will then proceed through
a sequence of self-diagnostics before
initiating a trial for ignition.
During the trial for ignition, the hot
surface ignitor will warm up.
Once the hot surface ignitor warms up, the
main gas valve will open allowing gas to
flow to the main burner.
Once the main burner ignites, the control
will verify that the burner flame is present
through the flame sense circuit. The hot
surface ignitor will then turn off.
The main burner will remain lit
throughout the heat cycle until the water
temperature setting is reached.
Once the water temperature setting is
reached, the control will close the main
gas valve which will extinguish the main
burner flames.
The blower motor will stay energized
for an additional 30 seconds after the
control verifies that the burner flame is
extinguished in order to clear combustion
gases from the water heater.
After the post-purge sequence, the control
will de-energize the blower motor and go
into a stand-by mode awaiting the next
call for heat.
This water heater is equipped with
a flammable vapor sensor that is
monitored continuously by the
electronic control in all modes of
operation.
In the event that flammable vapors are
detected, the control will automatically
shut down the water heater and prevent
the water heater from being started again.
The following is a list of materials that
will cause the Flammable Vapor Sensor
to shut down the water heater.
 Vapors of Gasoline.
 Vapors of certain flammable paints,
stains, and thinners.
 Vapors of vent pipe Cement &
Solvents.
 Bleach (direct contact with
flammable vapor sensor).
 Some other flammable materials and
their vapors.
If the flammable vapor sensor shuts
down the water heater, then the electronic
control will display the appropriate error
code and you should then promptly
contact a qualified service technician.
Refer to the “Notice” on page 3 for
additional information.