Two Stage Operation / Thermostat Selection Jumper; Tw0−Stage, Variable Speed Integrated Control Board; Thermostat Connections (Tb1); Dip Switch Functions - Lennox G60UHV Service Manual

After the 15−second pre−purge period, the SureLight ignitor
warms up for 20 seconds after which the gas valve opens
for a 4−second trial for ignition. The ignitor energizes during
the trial until flame is sensed. If ignition is not proved during
the 4−second period, the control will try four more times with
an inter purge and warm−up time between trials of 35 sec-
onds. After a total of five trials for ignition (including the ini-
tial trial), the control goes into Watchguard−Flame Failure
mode. After a 60−minute reset period, the control will begin
the ignition sequence again.
The SureLight control board has an added feature that pro-
longs the life of the ignitor. After a successful ignition, the
SureLight control utilizes less power to energize the ignitor
on successive calls for heat. The 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 control will again ramp down until the lowest
power is determined and the cycle begins again.

Two Stage Operation / Thermostat Selection Jumper

The control can be utilized in two modes: SINGLE−STAGE
thermostat or TWO−STAGE thermostat. The thermostat
selection jumper E20, located just below dip switches 1
through 3 (figure 4), must be positioned for the particular
application. The jumper is factory set on TWO" for use
with a two−stage thermostat with two stage heat. Re−posi-
tion jumper to SINGLE" for use with a single stage thermo-
stat with two stage heat.
While in the single−stage thermostat mode (single jumper
setting), the burners will always fire on first−stage heat. The
combustion air inducer will operate on low speed and in-
door blower will operate on low heat speed. After a 10 min-
ute recognition period, the unit will switch to second stage
heat. While in the two−stage thermostat mode (two jumper
setting) the burners will fire on first−stage heat. The com-
bustion air inducer will operate on low speed and indoor
blower will operate on low heat speed. The unit will switch
to second−stage heat on call from the indoor thermostat. If
there is a simultaneous call for first and second stage heat,
the unit will fire an first stage heat and switch to second
stage heat after 30 seconds of operation. See Sequence of
Operation flow charts in the back of this manual for more
detail.
TW0−STAGE, VARIABLE SPEED INTEGRATED
CONTROL BOARD
LEDs
DS8
DS3
DS7
ON−BOARD
JUMPER W914
CONTROL TERMINALS
(cut when SignatureStat,
CCB1 or Harmony II are used)

THERMOSTAT CONNECTIONS (TB1)

DIP SWITCH FUNCTIONS

DIP SWITCH(ES)
1 and 2 Blower Off Delay
3 Second Stage ON Delay (Single−stage t'stat)
4 Not used
5 and 6 Cooling Mode Blower Speed
7 and 8 Blower Speed Adjustment
9 and 10 Cooling Mode Blower Ramping Profile
11 and 12 Heating Mode Blower Speed
Page 10
DIAGNOSTIC
LEDs
FACTORY−
INSTALLED
JUMPER
ON−BOARD
16 PIN BLOWER
JUMPER W951
(cut when heat pump
is used with FM21)
FUNCTION
FIGURE 4
DIP
SWITCHES
1 − 3
E20
JUMPER
DIP
SWITCHES
5 − 12
LED
DS6