15
OPERATION
SEQUENCE OF OPERATION
Typical Control/Appliance Operating Sequence
1. When the control is initially powered, it enters a test mode and will
display the current software revision (example "104") for approximately
2 seconds, then "88.8" and all the LED's will illuminate for approximately
2 seconds. At this point, the control is in the idle mode and will display
the actual tank temperature.
2. If the control determines the actual water temperature inside the tank is
below the programmed temperature setpoint less one half the differential,
a call for heat is activated.
3. The control then performs selected system diagnostic checks. This
includes confirming the proper state of the air switch, ignitor, gas valve,
flame sense rod, and ECO limit device.
4. If all checks are successfully passed, the combustion blower is energized
for the pre-purge cycle.
5. When the pre-purge cycle is complete, power is applied to the ignitor
element for the ignitor warm-up period (blower should continue to run).
6. During the ignitor warm-up period, the control will sense ignitor current.
If ignitor current is within the specified range, the controller will energize
(open) the gas valve at the end of the ignitor warm-up period, allowing
gas to enter the burner chamber. If ignitor current is not within the
specified range, the control will not energize the gas valve, and the
control will return to Step 2 of the process. (See section below:
Appliance Ignition Failure).
7. After energizing the gas valve, the control will keep the ignitor on for a
short predetermined time period, then remove power to the ignitor.
8. After an additional 1 second, the control will monitor the flame sense
probe to confirm a flame is present. If a flame is not verified within this
time period, the controller will immediately de-energize (close) the gas
valve, and return to step two of the process. (See section below:
Appliance Ignition Failure).
9. If a flame is confirmed, the control will enter the heating mode where it
will continue heating the tank water until the setpoint temperature plus
one half the differential is reached. At this point, the gas valve is closed
and the control enters the post-purge cycle.
10.The combustion blower will run for the duration of the post purge cycle
to purge the system of all combustion gases. When the post purge
cycle is complete, the blower is de-energized and will coast to a stop.
11. The control will now enter the idle state while continuing to monitor the
internal tank water temperature and the internal state of the controller. If
the temperature drops below the setpoint value less one half the
differential, the control will automatically return to Step 2 and repeat the
entire operating cycle.
SELF DIAGNOSTIC CONTROLLER
A green LED is mounted on the Main Control Board to indicate line voltage
polarity is properly connected. The green LED is mounted next to connector
CN1 (Line input connection). When 120 VAC input power is properly
connected to the Main Control Board, the green LED will illuminate. If an
error is made when connecting 120 VAC input power, this LED will not light.
Improperly connecting the input power may result in a false sensor failure.
The 24 VAC circuitry is protected with a 3 amp auto fuse. If the fuse opens,
the LED display and discrete LED's on the Display Board assembly will not
illuminate. The recommended fuse replacement part is Littlefuse p/n 257003
automotive fuse. Repeated failure of the fuse is an indication of possible
damage to the Main Control Board. If repeated fuse failure occurs, return
the Control Board for service.
Under normal operating conditions, should the ignitor current fall out of
specification or the gas fail to light at the burner during the first trial for
ignition, the control will perform two (2) more ignition trials prior to entering
a lockout state. Note that each subsequent ignition trial will not occur
immediately. After a failed trial for ignition, the controller will remove all
power from the blower, gas valve, and ignitor and return to the call for heat
state. If a call for heat is activated, the controller will energize the combustion
blower for the pre-purge cycle, and again activate the ignitor to complete its
warm-up period. After the warm-up period, the gas valve is opened, ignitor
power removed, and the control will again check for flame.
If ignition is sensed during any one of these trials, normal operation will
resume. If ignitor current should fall out of specification or flame is not
sensed after the third ignition trial, the control will automatically enter a
lockout state ("Loc" displayed on the Display Board) and the ignitor or gas
valve LED on the Display Board will flash. The lockout state is manually
reset by momentarily pressing the push-button on the Display Board. If a
manual reset does not occur within a one hour time period, the controller
will automatically reset the lockout condition and provided the call for heat
still exists, will attempt another ignition sequence.
FIGURE 18
GAS VALVE LED FLASHING
FIGURE 17
14. Tubing-Pressure
15. Tubing-Pressure
17. Switch-On/Off
18. Low Gas Pressure Switch
(SUF 120 and 240 Only).
19. Bocked Inlet Switch
20. Wire Assembly-Air
Flow Switch
ITEM DESCRIPTION
1. Transformer
2. Control Board & Cable Ass'y
3. E.C.O./Temperature Probe
4. Blower Proving Air Switch
5. Low Voltage Cable Assembly
6. Line Voltage Cable Assembly
7. Blower/Motor Assembly
8. Igniter Assembly
10. Control Display Board
11.
Blocked Outlet Exhaust Switch
12. Lower Temperature Probe
13. Wire Assembly-Gas Pressure
Switch
Summary of Contents for SUF 100 150NE
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