035-17737-003 Rev. A (0504)
6
Unitary Products Group
Hot Surface Ignition System
FURNACE CLEANING SECTION
NOTE: THE CLEANING OPERATIONS LISTED BELOW MUST BE
PERFORMED ONLY BY A QUALIFIED SERVICE AGENCY.
Burner Removal/Cleaning
The main burners should be checked periodically for dirt accumulation.
If cleaning is required, follow this procedure:
1.
Turn off the electrical power to the unit.
2.
Turn off the gas supply at the external manual shut-off valve and
loosen the ground union joint.
3.
Remove the burner door and remove the burner box cover.
4.
Disconnect wires from flame sensor, rollout switch and HSI igniter.
Remove igniter carefully, as it is easily broken.
5.
Remove the screws that hold the burner box assembly to the vest
panel and remove the assembly.
6.
Remove burners from the burner assembly.
7.
Burners may be cleaned by rinsing in hot water.
8.
Reassemble the burners in the reverse order.
Cleaning the Heat Exchanger
1.
Turn off the electrical power to the unit.
2.
Turn off the gas supply at the external manual shut-off valve and
loosen the ground union joint.
3.
Remove the burner door and remove the burner box cover.
4.
Disconnect wires from flame sensor, rollout switch and HSI igniter.
Remove igniter carefully, as it is easily broken.
5.
Remove the screws that hold the burner box assembly to the vest
panel and remove the assembly.
6.
Remove the vent pipe assembly, vent blower and condensate pan.
7.
The heat exchanger is now exposed.
8.
With a long flexible wire brush, clean inside each tube at both the
top and bottom. The brush must pass around the rear heat
exchanger tubes. Then vacuum loose the scale and dirt from each
tube.
9.
Replace all components in reverse order. Reconnect all wiring.
10. Restore electrical power and gas supply to the furnace.
11.
Check furnace operation.
Cleaning the Secondary Heat Exchanger
1.
Follow steps 1 - 7 under cleaning the Heat Exchanger.
2.
Remove the vent piping from the vent blower housing. Disconnect
the drain lines from the vent blower housing and from the conden-
sate drain pan. Remove the vent blower housing blower and the
condensate pan.
3.
Using a stiff wire brush, remove the loose scale or soot from each
tube.
4.
Vacuum the secondary heat exchanger.
5.
Finish the cleaning procedure by following steps 9 - 11 under
cleaning the Heat Exchanger.
TROUBLESHOOTING
The following visual checks should be made before troubleshooting:
1.
Check to see that the power to the furnace and the ignition control
module is ON.
2.
The manual shut-off valves in the gas line to the furnace must be
open.
3.
Make sure all wiring connections are secure.
4.
Review the sequence of operation. Start the system by setting the
thermostat above the room temperature. Observe the system’s
response. Then use the troubleshooting section in this manual to
check the system’s operation.
FURNACE CONTROL DIAGNOSTICS
The furnace has built-in, self-diagnostic capability. If a system problem
occurs, a blinking LED shows a fault code. The LED can flash red,
green or amber to indicate various conditions. It is located behind a
clear view port in the blower compartment door.
The control continuously monitors its own operation and the operation
of the system. If a failure occurs, the LED will indicate the failure code. If
the failure is internal to the control, the light will stay on continuously. In
this case, the entire control should be replaced, as the control is not
field repairable.
Flash sequence codes 1 through 10 are as follows: LED will turn “on”
for 1/4 second and “off” for 1/4 second. This pattern will be repeated the
number of times equal to the code. For example, six “on” flashes equals
a number 6 fault code. All flash code sequences are broken by a 2 sec-
ond “off” period.
SLOW GREEN FLASH:
Normal operation.
SLOW AMBER FLASH:
Normal operation with call for heat.
RAPID RED FLASH:
Twinning error, incorrect 24V phasing. Check
twinning wiring.
RAPID AMBER FLASH:
Flame sense current is below 1.5 microamps.
Check and clean flame sensor. Check for proper gas flow.
1 RED FLASH:
This indicates that flame was sensed when there was
not a call for heat. With this fault code the control will turn on both the
inducer motor and supply air blower. A gas valve that leaks through or
is slow closing would typically cause this fault.
2 RED FLASHES:
This indicates that the normally open pressure
switch contacts are stuck in the closed position. The control confirms
these contacts are open at the beginning of each heat cycle. This would
indicate a faulty pressure switch or miswiring.
3 RED FLASHES:
This indicates the normally open pressure switch
contact did not close after the inducer was energized. This could be
caused by a number of problems: faulty inducer, blocked vent pipe, bro-
ken pressure switch hose or faulty pressure switch.
HOT SURFACE IGNITION SYSTEM
Do not attempt to light this furnace by hand (with a
match or any other means). There may be a potential
shock hazard from the components of the hot surface
ignition system. The furnace can only be lit automatically
by its hot surface ignition system.
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and danger-
ous operation. Verify proper operation after servicing.
Never bypass any safety control to allow furnace opera-
tion. To do so will allow furnace to operate under poten-
tially hazardous conditions.
Do not try to repair controls. Replace defective controls
with UPG Source 1 Parts.
Never adjust pressure switch to allow furnace operation.
