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a−Electronic Ignition (See Figure 7)
On a call for heat the ignition control board monitors the
combustion air inducer prove switch. The ignition control
will not begin the heating cycle if the prove switch is closed
(by−passed). Once the proving switch is determined to be
open, the combustion air inducer is energized. When the
differential in the prove switch is great enough, the prove
switch closes and a 15−second pre−purge begins. If the
prove switch is not proven within 2−1/2 minutes, the control
goes into a 5 minute prove switch reset period.
After the 15−second pre−purge period, the ignitor warms up
for 20 seconds then the gas valve opens for a 4−second trial
for ignition. The ignitor stays energized during the trial until
flame is sened. If ignition is not proved during the 4−second
period, the ignition control will try four more times with an in-
ter purge and warm−up time between trials of 35 seconds.
After a total of five trials for ignition (including the initial trial),
the ignition control goes into Watchguard−Flame Failure
mode. After a 60−minute reset period, the ignition control will
begin the ignition sequence again.
The ignition control has an added feature that prolongs the
life of the ignitor. After a successful ignition, the ignition con-
trol utilizes less power to energize the ignitor on successive
calls for heat. The ignition control continues to ramp down
the voltage to the ignitor until it finds the lowest amount of
power that will provide a successful ignition. This amount of
power is used for 255 cycles. On the 256th call for heat, the
ignition control will again ramp down until the lowest power
is determined and the cycle begins again.
b−Fan Time Control Heating
The heating fan on time of 45 seconds is not adjustable. Fan
off time (time that the blower operates after the heat de-
mand has been satisfied) can be adjusted by setting the S1
dip switches (switches 1 and 2) located on the ignition con-
trol. The unit is shipped with a factory fan off setting of 90
seconds. Fan off time will affect comfort and is adjustable to
satisfy individual applications. For customized comfort,
monitor the supply air temperature once the heat demand is
satisfied. Note the supply air temperature at the instant the
blower is de−energized. Adjust the fan−off delay to achieve a
supply air temperature between 90° − 110° at the instant the
blower is de−energized. (Longer delay times allow for lower
air temperature, shorter delay times allow for higher air tem-
perature). See table 7 for switch settings and fan delay
times..
c−Fan Time Control Cooling
The cooling fan on time is fixed at 2 seconds and cannot be
adjusted. Fan off time (time that the blower operates after
the cool demand has been satisfied) is factory set at 2 sec-
onds but can be adjusted by setting the S1 dip switches
(switch 3) located on the SureLight integrated control. See
table 7 for switch settings and fan delay times.
TABLE 7
S1 DIP SWITCH SETTINGS
Heat Off Delay
Switch 1 Switch 2 SECONDS
OFF OFF 60
OFF ON 90
ON OFF 120
ON ON 180
Cool Off Delay
Switch 3 SECONDS
OFF
(factory setting)
2
ON 45
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