controls have on-board twinning.
Both controls use DIP switches to
select the blower off timing. They
come set for 120 seconds of blower
operation after the heat call ends.
Both controls have the
"self-
healing"
feature.
Except for the ignition method. the
operating characteristics are very
similar to the hot surface ignition
controls used with previous 90 Plus
furnaces.
1. As with other electronic controls,
furnace grounding and line
voltage polarity are critical for
proper operation.
2. If this control does not detect
ignition after two attempts. it
goes into a
"self healing" mode
and operates both the main
blower and induced draft blower
for 180 seconds. It then
attempts a third ignition trial.
3. If there are four failed attempts
for ignition, or four flame failures
during one heat call, the control
goes into a
"soft lock out."
4. A "soft lock out" can be reset by
cycling main power on and off.
or by cycling 24 volt power at
the thermostat.
5. The control automatically resets
after one hour in "soft lock out."
►
NOTE: The UTEC 1028-927 has
been replaced by the
1028-928
(62-24140-02)
control. It's serial
numbers begin with
EJ or EL The
Johnson Controls G961 DAJ-2401
control has been replaced by the
G961DAJ-2402 (62-24136-02)
control. It's serial numbers begin with
EH or EK. Both controls function the
same as those they replaced and
came into service in 1999.
The new
controls have a replaceable 3 amp
automotive-type fuse to protect 24
volt components on the board.
Sequence of Operation
Prepurge -
1. The thermostat calls for heat.
2. The induced draft blower (IDB)
starts and operates for the entire
heat call.
3. The pressure switch(es) close.
4. The inducer operates for a 30
second pre-purge.
Ignition Trial -
1. The gas valve opens and the
igniters spark.
1
I FIGURE 97
JOHNSON CONTROLS G961 DAJ-2401 OSI FURNACE CONTROL
-< >-..
0 (!)~'
~
::0 0: 1..,
, ,
I
2. The igniter sparks for up to 7
seconds after the gas valve
opens, or until flame recognition.
3. The burners ignite.
Flame Recognition -
1. The flame sensor recognizes
ignition using the process of
flame rectification.
2. If flame is not proved in eight
seconds, the gas valve closes
and the IDB runs for a 30
second inter purge.
Operation -
1. The main blower starts 20
seconds after sensing flame.
2. The inducer and burners
continue to operate.
Shut down -
1. The thermostat call ends.
2. The gas valve closes and the
burners go out.
3. The IDB runs for a 5 second
post purge.
4. The main blower operates until
timed off by the IFC.
TROUBLESHOOTING
Indicator Lights
The "OK" light has troubleshooting
features. If a specific problem takes
the furnace off line, the light flashes
a certain number
of times to indicate
the problem.
The following lists the sequence of
"OK" light flashes and the associated
problem.
1. One blink followed by a 2 sec.
pause - soft (one hour) lock out.
2. Two blinks follow~d by a 2 sec.
pause - open pressure switch.
3. Three blinks followed by a 2 sec.
pause - open limit switch.
4. Four blinks followed by a 2 sec.
pause - shorted pressure switch.
5.
►
Five blinks followed by a 2
sec. pause - improper twinning.
IFC IGNITION TRANSFORMER
Each OSI IFC has a high voltage
output transformer that generates the
spark needed to light the burners.
The wire to the igniter simply "stabs"
onto the IFC transformer spike
connection.
A CAUTION: DO NOT TOUCH
THE IGNITION TRANSFORMER.
IGNITER WIRE, OR THE
IGNITERS. THE TRANSFORMER
OUTPUTS AN EXTREMELY HIGH
DC VOLTAGE. SERIOUS
PERSONAL INJURY CAN RESULT.
FIGURE 98
DSIOUTPUTTRANSFORMER
80
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