16
9. The furnace is now operating on the specified stage
called out by the two stage thermostat.
10. If the two stage thermostat changes the call from low
heat to high heat, the control will immediately switch the
induced draft blower gas valve, and air circulating
speed to their high stage setting.
11. If the two stage thermostat changes the call from high
heat to low heat, the control will immediately switch the
induced draft blower to low speed and switch the flow
rate on the gas valve to low. The air circulation blower
will remain on high heating speed for thirty seconds
before switching to the low heat circulating speed. The
30 second delay feature on the circulator speed elimi-
nates the possibility of tripping the high (primary) limit
when the high stage flue products are traveling through
the heat exchanger upon a call for low stage heat.
12. The two stage thermostat is satisfied and opens.
13. The control turns the gas valve off.
14. After a five second delay while flue products are purged
from the heat exchanger, the induced draft blower is
turned off (the induced draft blower is on low speed
during the first five seconds post purge).
15. The air circulation blower has an adjustable delay-off
timing of 60, 90, 120, or 180 seconds (starting from the
time the gas valve closes). The speed(s) run during this
period depend on the last heat call seen by the thermo-
stat.
If the last call for heat was a call for low heat, the air
circulation blower will run on the low heat speed for the
duration of the adjusted delay-off timing (60, 90, 120, or 180
seconds).
If the last call for heat was a call for high heat, the air
circulation blower will run on the high heating speed for
thirty seconds and then switch to the low heating speed for
the
balance
of the adjusted delay-off timing (30, 60, 90, or
150 seconds).
Example: A GUIS090CA50 has the air circulation blower off
delay set to 120 seconds by the installer. When the thermo-
stat is satisfied after a call for high heat, the air circulation
blower will run on high speed for 30 seconds and then
switch to low circulator speed for 120 - 30 = 90 seconds.
The adjustable delay-off timing allows more heat trans-
ferred to the conditioned space from the furnace. After the
delay time has elapsed, the air circulation blower is de-
energized. The adjustable delay-off timing feature allows
the installer to customize the comfort level based on the
predominant staging requirements of the living space.
IX. Start-Up, Adjustments, and Checks
GENERAL OPERATION
This furnace is equipped with an electronic ignition device
to light the burners and an induced draft blower to exhaust
combustion products.
An interlock switch prevents furnace operation if the blower
door is not in place. Keep the blower access doors in place
except for inspection and maintenance.
This furnace is also equipped with a self-diagnosing elec-
tronic control module. In the event a furnace component is
not operating properly, the control module LED will flash
on and off in a factory-programmed sequence, depending
on the problem encountered. This light can be viewed
through the observation window in the blower access door.
Refer to the
Diagnostic Signal Chart
for further explanation
of the lighting codes and Section IX,
Abnormal Operation -
Integrated Ignition Control
for an explanation of the pos-
sible problem.
On new installations, or if a functional part such as the gas
valve, pressure switch, or limit control has been replaced,
the operation of the furnace should be checked.
Check furnace operation as outlined in the following in-
structions. If any sparking, odors, or unusual noises are
encountered, shut off electrical power and recheck for
wiring errors, or obstructions in or near the blower motors.
Various shipping materials must be removed before the
blower motor is operated.
ROLLOUT PROTECTION DEVICE
IMPORTANT NOTE:
This furnace is equipped with a device
to close the gas valve if the burner flames are not drawn into
the heat exchanger.
GUI_
furnaces installed horizontal
right-to-left airflow, the device must be relocated.
GCI_
furnaces installed horizontal left-to-right airflow, the device
must be relocated.
S upply
A ir
R eturn
A ir
Figure 28
Right To Left Installation
S upply
A ir
R eturn
A ir
Figure 29
Left To Right Installation
If relocation is required, proceed as follows:
1. Disconnect electrical power.
WARNING
To prevent death or personal injury due to
electric shock, disconnect electrical power.
2. See Figures 30 & 31. Remove the cover from the burner
box. Save the screws that held it in place. (
Note:
There
are several screw holes, but only four screws. This is
intentional, and not a manufacturing defect.)
3. As shipped, the rollout protection device is located near
the flame sensor end of the manifold assembly. Re-
move and save the mounting screws.
4. For most installations, it will not be necessary to remove
the wires from the rollout protection device.
