Reznor R6GF Unit Installation Manual - Manual (Page 20)

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the inducer has been off for 60 minutes, the control
energizes the inducer motor and restarts the 60 second
pressure switch proving period.
5. Pre-Purge - If the low pressure switch closes the control
runs the inducer on high speed for a 30 second pre-purge
time while monitoring the thermostat call for heat, limit
switch circuit, low pressure switch, and flame sense.
High pressure switch is ignored.
6. Igniter Warm Up - When the 30 second pre-purge time
has elapsed, the control begins the Hot Surface Ignition
(HSI) warm-up as follows:
Initial Power up: After 30 seconds of igniter warm-up,
the gas valves (24 VAC) will open. The igniter circuit will
stay energized for 3 seconds after the gas valve opens.
After Initial Power up: The control has a programmed
adaptive ignition feature which varies the warm-up
period as follows: If ignition is successful the warm-up
is reduced by 3 seconds on each subsequent call for
heat until ignition failure occurs. Upon ignition failure,
the warm-up is increased by 3 seconds on the next try.
If successful, the timing remains fixed at this level. In
general, whenever ignition failure occurs the warm-up
interval is increased by 3 seconds on the next try. And
if successful, it remains there. Minimum and maximum
warm-up time limits are set at 9 and 54 seconds.
7. Flame Proving / Ignition / Low Heat Operation - The
furnace control must prove flame via the flame sensor
5 seconds after the low main gas valve is energized. If
flame is sensed, burners are on and the igniter cools off.
If no flame is sensed, the gas valve closes immediately
and the inducer continues to run. A second trial for
ignition (step 6) begins. If no flame is sensed on the
fifth try for ignition, the furnace control is locked and the
red LED will flash 4 times repetitively. The thermostat
must be opened for at least ten seconds to reset the
furnace control after a lock out. Otherwise, the furnace
will attempt another ignition sequence in 1 hour.
Low Fire Heat (Stage 1): If flame is present at the end
of the trial for ignition time, the control leaves Low main
gas valve energized, inducer motor on High speed for the
first 15 seconds, and begins the heat blower on delay.
Control inputs are continuously monitored while the call
for heat remains. The control will always energize the
gas valve on Low fire with the inducer on high speed for
the first 15 seconds of any heating cycle and ignores
any second stage heat demand. After this 15 second
period, the control switches inducer to Low speed if no
second stage demand is present, or attempts to stage
to high heat if thermostat W2 terminal is energized.
8. Blower Start-Up - After flame is proven, the furnace
control energizes the circulating air blower at a very
low speed. After 30 seconds, the blower will ramp to
the airflow selected for heating.
9. High Heat Staging (with 2 Stage Heat Thermostat) - Unit
will always start in low heat operation. See step 7 for
start up sequence. After the initial 15 second start up
sequence is satisfied, the control will wait for a W2 call
from a 2-stage thermostat. After a second stage heat
demand is present (W2 energized), the gas valve will
open to High heat mode increasing the flow of gas to
the burners while the inducer and blower motor ramp
to high speed.
Single Stage Heat Thermostat with Automatic Heat
Staging - Automatic heat staging allows the unit to
operate as a two stage gas furnace with the use of a
single stage heating thermostat. With the ignition control
AUTO HEAT STAGE jumper repositioned across the
desired delay in minutes, 5 or 10, the gas furnace will
automatically switch to high heat mode of operation.
The induced draft motor and blower motor will both
ramp to high speed. See Figure 11B (page 28).
10. When the thermostat has been satisfied, gas valve is
de-energized.
11. The inducer motor is de-energized after a 30 second
post purge.
12. The circulating air blower will remain energized for
approximately 120-150 seconds after the demand
for heat is no longer present.
13. Abnormal Conditions - If a limit switch opens during
heating operation the gas valve is de-energized
immediately. The control de-energizes the induced
draft motor and runs the indoor blower motor
continuously while the limit switch is open.
Cooling Mode
1. On a call for cooling the thermostat closes, applying
24 VAC to the G & Y1 terminals on the control. This
closes the compressor contactor and the compressor
operates in 1st stage.
2. The control energizes the circulating blower to 1/3 of
the selected airflow for approximately 30 seconds.
3. The circulating blower will then ramp to approximately
3/4 of the selected airflow for another 30 seconds before
adjusting to full airflow until the thermostat is satisfied.
4. If the thermostat is not satisfied in the required time,
based on the operation of the two-stage cooling
thermostat, Y2 will energize and the compressor will
run at second stage and the circulating blower will ramp
up to high speed. Refer to the thermostat installation
instructions for the cooling profile.
5. When the thermostat is satisfied, the G & Y terminals
on the control board are de-energized opening the
compressor contactor.
6. The circulating air blower will operate at 1/2 of the
selected speed for 60 seconds, and de-energize.
Fan Mode
1. On a call for fan operation, the thermostat applies 24
VAC to the G terminal on the furnace control board.
2. The circulating air blower ramps to 1/2 of the selected
airflow.