24
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OPERATION IN RUN MODE
Start-up sequence
When a fuel selection is made and the burner select signal is given to start up the burner, the control
unit runs through the sequence described below. If gas is the selected fuel and gas valve proving has
been selected, the unit also performs safety valve pressure proving in parallel with the start-up
sequence (see option parameter 2.0 Gas Pressure Select).
STAGE NO.
STAGE NAME
DESCRIPTION
0 Safety
Shutdown
The burner is held in this state until all faults are removed.
1
Burner Off
The burner is checked to make sure that it has switched off completely. This includes main fuel
safety valves closed, no flame signal and a no air pressure signal.
2
Wait for Purge
The unit waits for a both burner select and a gas or oil select signal.
3
Open Fuel Valve
If gas valve proving is selected, the fuel motor is moved up for five seconds to allow any gas in the
test section to be vented easily during the proving sequence.
4
Hold Fuel Valve
The fuel motor is held in position until step 1 of the safety valve proving sequence (open main valve
2, or vent valve) is completed.
5
Prove Closed
Position
If gas is selected, the gas valve proving sequence begins. The fuel and air motors are moved down
until they stop. The final positions are compared with the closed positions stored in memory.
6
Prove Air
Pressure
The fuel and air motors are moved up towards the purge position, the burner motor is started and
air pressure prove time t1 is initiated.
7
Prove Purge
Positions
When the air pressure prove time t1 has elapsed, the air pressure switch must give a ‘pressure’
signal or the unit will lockout the burner. If firing on oil and primary air is selected, both primary
and secondary air signals must change from ‘no pressure’ status. If firing on gas and primary air is
selected the primary air signal must remain at ‘no pressure’ status.The fuel and air motors are
moved up until they stop. The unit measures the time taken for each motor to travel from the close
to the purge position and the final measured positions are compared with the purge positions
stored in memory.
8
Pre-Purge
The timed pre-purge t2 is initiated. The fuel motor is moved towards the closed position during this
time.
9
Move to Ignition
Positions
When t2 has elapsed, the fuel and the air motors are moved to the ignition position for the selected
profile. The unit will wait for the gas valve proving sequence to finish if it is still in progress
10
Pre-Ignition
Once the fuel and air motors are at their ignition positions, the ignition transformer output is ener-
gized and pre-ignition time t3 is initiated.
11
Pilot Ignition
Once t3 has elapsed the ignition transformer, pilot valve outputs are energized and the first safety
time t4 is initiated. If oil is selected, use timing in the start-up sequence table for main valve 2.
12
Pilot Ignition
Interval
When the first safety time t4 has expired, a flame must be detected or the unit will lockout the
burner. The ignition transformer output is turned off and interval time t5 is initiated.
13
Main Ignition
Once the pilot interval time t5 has elapsed, both main valve outputs for gas, main oil valve output
for oil is energized and the second safety time t6 is initiated.
14
Wait for Flame
Established
When the second safety time t6 has expired, the pilot valve output is turned off. If permanent pilot
is selected and the burner is firing on gas the pilot will remain open with main valve 2. Main interval
time t7 is initiated.
15
Moving to Low
Fire
When interval time t7 has elapsed, the flame is considered established and the fuel and air motors
are moved from their ignition positions to their low fire positions.
16
Modulation
Once the fuel and air motors reach their low fire positions, they are modulated according to the
demand placed on the burner.
17
Move to Post-
Purge
If the fuel selection is changed or the ‘burner on’ signal is removed, the main valve outputs are
turned off. The fuel motor is moved to its closed position, the air motor is moved to its purge posi-
tion and the post purge time is initiated.
18
Post-Purge
When the post purge time has elapsed, the burner motor is turned off and the unit returns to stage
1 to wait for another start-up.
