17
BURNER OPERATION
BURNER STARTING
• Load control close.
Fan motor starts.
• Servomotor starts:
130° rotation to right, until contact is made on cam
1)(A) page 13.
The air damper is positioned to MAX. output.
• Pre-purge stage with air delivery at MAX. output.
• After pre-purge stage, servomotor rotates to left up to
the angle set on cam 3)(A) page 13 for MIN. output.
• The air damper and the gas butterfly are positioned to
MIN. output.
• Ignition electrode strikes a spark.
• Pilot valve opens. The pilot flame is ignited.
• After about 12 s the main flame ignites and starting
cycle ends.
STEADY STATE OPERATION
At the end of the starting cycle, the servomotor control
then passes to the load control for boiler pressure or
temperature.
(The control box continues, however, to check that the
flame is present and that the air pressure switch is in the
correct position.)
• If the temperature or pressure is low, the burner pro-
gressively increases its output to the MAX. value.
• If the temperature or pressure is high, the burner pro-
gressively decreases its output to the MIN. value.
And so on.
• The burner locks out when demand for heat is less
than the heat supplied by the burner at min. output.
Load control opens. The servomotor returns to the 0°
angle limited by contact with cam 2. The air damper
closes completely to reduce thermal dispersion to a
minimum.
Every time output is changed, the servomotor automati-
cally modifies gas delivery (gas butterfly valve) and air
delivery (fan air damper).
Switching times are given in seconds, in the burner star-
tup sequence.
Legend for the times
t1
Pre-purge time with air damper open
t2
Safety time
t3
Pre-ignition time, short (ignition transformer on
terminal 16)
t4
Interval between start of t2 and release of valve
at terminal 19
t5
Interval between end of t4 and release of load
controller or valve at terminal 20
t5
Running time of air damper into OPEN position
t6
Running time of air damper into low-flame posi-
tion (MIN)
t7
Permissible after-burn time
t8
Interval until OPEN command for the air damper
is given
FIRING FAILURE
If the burner does not fire, it locks out within 2.5 seconds
from opening the pilot valve and then within 5 seconds
from opening the main valves.
BURNER FLAME GOES OUT DURING OPERATION
If the flame should accidentally go out during operation,
the burner will lock out within 1s.
LFL 1.335
Series 01
t1
t2
t3
t4
30
2
4
20
t5
t6
t7
t8
optional
optional
12
4
(A)
Full Modulation
D2273
Low - High
D2274
(B)
LFL 1.335
Series 01
