Startup Procedure; Sequence Of Operations - Rheem R95P Installation Instructions Manual

This furnace is equipped with a direct ignition control. Each
time the room thermostat calls for heat, the ignitor lights
the main burners directly. See the lighting instructions on
the furnace.
TO START THE FURNACE
1. Remove the burner compartment control access door.
2. IMPORTANT: Be sure that the manual gas control has
been in the "OFF" position for at least five minutes. Do
not attempt to manually light the main burners.
3. Turn off the furnace electrical power and set the room
thermostat to its lowest setting.
4. Turn the gas control to the "ON" position or move the
gas control lever to the "On" position.
5. Replace the burner compartment control access door.
6. Turn on the furnace electrical power.
7. Set the room thermostat to a point above room temper-
ature to light the main burners.
8. After the burners are lit, set the room thermostat to a
desired temperature.
9. Operate gas heat for a minimum period of 15 minutes
and adjust input rate (page 88) and observe conden-
sate system for leaks. Correct leaks and set rate, shut-
down furnace and repeat until no leaks in condensate
system can be detected.
TO SHUT DOWN THE FURNACE
1. Set the room thermostat to its lowest setting and wait
for furnace to shut down.
2. Remove the burner compartment control access door.
3. Shut off the gas to the main burners by turning the gas
control to the "OFF" position.
SHOULD OVERHEATING OCCUR OR THE GAS SUP-
PLY FAIL TO SHUT OFF, CLOSE THE MANUAL GAS
VALVE FOR THE APPLIANCE BEFORE SHUTTING
OFF THE ELECTRICAL SUPPLY. FAILURE TO DO SO
CAN CAUSE AN EXPLOSION OR FIRE RESULTING
IN PROPERTY DAMAGE, PERSONAL INJURY OR
DEATH.
86
SEQUENCE OF OPERATION
UT ELECTRONIC CONTROLS
Integrated Controls with Direct Spark Ignition.
1. Each time the thermostat "W" (Heating) contacts close,
the furnace control checks to make sure the pressure
switch is open. Next the induced draft blower (inducer)
begins a prepurge cycle.
2. The air proving negative pressure switch(es) closes.
3. After the 30-second pre-purge, the gas valve opens
for an 8-second trial for ignition.
4. The spark igniter is energized to light the gas burners
and stays energized for the up to 7 seconds after
the gas valve opens.
5. 8 seconds after the gas valve opens the remote flame
sensor must prove flame ignition for one second
using the process of flame rectification. If the burners
don't light, the system goes through another ignition se-
quence. It does this up to four times before entering a
1-hour lockout.
6. The main blower starts approximately 20 seconds after
the burners ignite.
7. When the thermostat "W" (Heat Call) ends, the gas
valve closes, flame is extinguished, the induced draft
blower stops after a 10-second post-purge, and the
negative pressure switch opens.
8. The main blower continues until timed off by the setting
on the integrated furnace control board.
Sequence if the system doesn't light or doesn't sense
flame:
1. On a call for heat, the furnace control checks to make
sure the pressure switch is open. Next the control runs
the inducer for 30 seconds to prepurge.
2. After the 30-second pre-purge, the gas valve opens for
an 8-second trial for ignition. The inducer continues and
the igniter stays energized.
3. If flame is not sensed during the 8th second after the
gas valve opens, the gas valve closes, and the igniter
de-energizes.
4. The inducer stops (may take up to 20 seconds for in-
ducer fan to stop rotating) and the control verifies that
the pressure switch has opened. Once the open pres-
sure switch is confirmed, the control begins the next ig-
nition cycle by energizing the inducer for a pre-purge of
30 seconds. After a 30-second pre-purge period, the
gas valve is energized and the control looks for a flame
signal for up to 8 seconds. If no flame is sensed, the
cycle is repeated up to 4 times before entering a 1-hour
lockout.