Rheem Power Direct Vent Series, Use & Care Manual

Page: 31 / 40

31
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 vent pres-
sure switch is open, the control will ener-
gize the blower motor for the pre-purge
sequence (approximately 5 seconds).
The control will verify that the vent pres-
sure 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 initi-
ating a trial for ignition.
During the trial for ignition, the hot sur-
face 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 con-
trol 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 con-
tact a qualified service technician.
Refer to the “Notice” on page 3 for addi-
tional information.