TM 5-3895-374-24-2
5.
When the firing rate motor reaches its open damper position, the Hi Purge switch closes (D-8) and
initiates the prepurge interval of 30 seconds. If the D-8 circuit does not close, the program will hold
in this position for ten minutes waiting for it to close. If it does not, the control will lockout.
6.
When the prepurge is completed, the firing rate motor is driven toward the low purge damper posi-
tion (10-12 ckt. made).
7.
Following the minimum 30 second delay (to permit the firing rate motor to get to the low fire posi-
tion), the control will wait for the low fire switch (M-D) to close. When it closes, the trial for igni-
tion sequence will start If after ten minutes, the M-D circuit is not closed, the control will lockout.
8.
The trial for ignition period begins with Terminal 5 and 6 being energized simultaneously. This
is known as PTFI (Pilot Trial for Ignition). This period is ten seconds in duration. If no flame is
detected after ten seconds, the control will de-energize Terminals 5 and 6 and lockout. If flame is
detected during this 10 second period, the main flame trial for ignition sequence will start
Note: When the flame is detected. the message center will provide a constant readout of the signal
strength.
Flame Signal
0-9
Not Acceptable
10
Minimum Acceptable
20-80
Normal
9.
With flame proven at the end of PTFI, the main flame trial for ignition (MTFI) period begins. Ter-
minal 7 is energized. Terminal 5 is de-energized 10 seconds later and Terminal 6 is de-energized
after another 5 seconds.
1.
The firing rate motor is now sent to the auto position (10-11 ckt mode) and is under the command
of the proportional controller. The message center displays a read-out of the flame signal.
Normal Shutdown
1.
When the operating control circuit (Ll-13) opens, the main fuel valve is de-energized. The firing
rate motor is driven to the low purge position (10-12 ckt mode).
2.
Following a 15 second post purge, the burner/blower motor is de-energized.
3.
The burner is now off and the message center displays the burner operating history for two minutes
and then the message center displays the message "OFF."
LOCKOUTS
When a safety shutdown occurs, the control will display a message indicating LOCKOUT and the
reason for the lockout. The alarm circuit (Terminal "A") will be energized. The non-volatile memory
will remember the status of the control even if a power failure occurs. By depressing the button just
above the display, the control can be reset. The button must be held down for one second and then
released. Very little force is required to do this. Do not press hard.
Safety Shutdown
1.
If the running interlock circuit does not close, the control will lockout and the blower motor will
be de-energized. If the interlock circuit opens during a start-up or firing period, all fuel valves will
be de-energized and the control will lockout.
2.
If pilot flame is not detected during the 10 second trial for ignition period, the pilot valve and igni-
tion transformer will be de-energized and the control will lockout on safety.
3.
If main flame is not detected at the end of the main flame trial for ignition period, all fuel valves
will be de-energized and the control will lockout on safety.
4.
If the main flame fails during a firing cycle, all fuel valves will be de-energized within 4 seconds
after loss of flame signal and the control will lockout on safety.
5.
A flame seen at an improper time will cause a lockout.
6.
Additional lockout messages and causes are described in the following pages.
Note: Manual Reset is required following any safety shutdown.
FLAME SAFEGUARD
(page 3 - 1045)
