36
£
Terminal 21 is used to hold the system indefinitely at the end of low fire start and when opened will
initiate pilot trial for ignition. Assuming the count method is set for down, at the end of a low fire
start period the display will indicate:
HOLD
00:00
T21 INPUT CLOSED
During the AUTO or RUN position, terminal 21 can be used to force the firing motor to the low fire
position. In this state the display will indicate:
HOLD T21 42
top line indicates hold mode with flame signal
LOW FIRE SIGNAL
Terminal 16 is used to hold the system in a pilot proving state following the pilot trial for ignition
period. After pilot trial for ignition, as determined by the PTFI*MTFI TIMING selection, terminal 5
will be de-energized and terminal 6 will remain energized. During this state the system is in a flame
proven state and the display will indicate:
PILOT
42
flame signal displayed
T16 INPUT CLOSED
pilot hold period
Once terminal 16 is released or de-activated, the system then proceeds in the MTFI period in accor-
dance with the PTFI*MTFI TIMINGS selection. If selected to be on, terminal 5 with the ignitor will
become energized during MTFI.
Terminal 16 is also used to revert the system back to the pilot proving mode from the AUTO or RUN
mode. During AUTO, an active state on terminal 16 initiates the steps to revert back to pilot mode.
On detection of terminal 16, the firing rate motor is commanded to the low fire position and the sys-
tem waits for the low fire start switch (M-D) to close. While in this wait mode the display indicates:
HOLD T16
42
while in AUTO, Terminal 16 closes
M-D LIMIT OPEN
wait for low fire interlock to close
Once the low fire start switch is detected as closed, terminal 6 is energized to open the pilot valve. A
20 second time delay is then imposed with both the main valve (7) and pilot valve (6) energized. The
display will indicate:
HOLD T16
42
while in AUTO, M-D detected closed
M-D LOW LIMIT
wait 20 seconds in this state
At the end of the 20 seconds, the main valve (7) is de-energized and the ignition terminal (5) is ener-
gized for the time specified in PTFI*MTFI TIMINGS. Terminal W is energized for 5 seconds. The
display will indicate:
PTFI
42
flame signal displayed
FLAME SIGNAL
Unlike PTFI, this period is a flame proven state and if flame signal is lost for one FFRT, the system
will shutdown and lockout. At the end of the selected PTFI time, terminal 5 is de-energized and the
system proceeds to the pilot proving period with terminal 6 energized and flame being proven. The
display will indicate:
PILOT
42
flame signal displayed
T16 INPUT CLOSED
pilot hold period
Once terminal 16 is de-energized, the system proceeds into the MTFI period with terminal 7 (main
valve energized). If selected to be on, terminal 5 with the ignitor will become energized during MTFI
in accordance with the PTFI*MTFI TIMINGS selection. At the conclusion of the MTFI period and
as selected by PTFI*MTFI TIMINGS selection and terminal 6 as interrupted/intermittent, terminals
5 and 6 assume their respective states.
