Advertisement
Function
Prerequisites for
burner startup
Program sequence
on startup
Startup with ignition
spark supervision
Building Technologies
The burner can be started only when:
the burner control's sequence switch is in its start position
-
the burner control has not locked out, e.g. caused by a defective UV tube
-
-
the contacts of all control and safety devices in the control loop between terminals
8 and 9 are closed
the air pressure switch does not indicate air pressure
-
Defects in the flame supervision circuit or in the burner control itself prevent startup or
lead to lockout during the startup sequence.
Attention!
If the air damper is not controlled by the burner control, terminals 20, 21 and 22
must be interconnected.
First, the fan motor is activated via terminal 3, and the actuator is controlled via terminal
22.
As soon as the air damper reaches its fully open position, the burner control's
sequence switch starts running and the prepurge time commences.
The minimum air pressure set on the air pressure switch must be reached within 10
seconds (5 seconds with the LFE1.1) (or 7 seconds [3.5 seconds with the LFE1.1] with
postpurging) and must be maintained until controlled shutdown occurs. Otherwise, the
burner control will initiate lockout.
A flame signal during the prepurge time also leads to lockout.
On completion of the set prepurge time, the damper receives the control command to
return to the fully closed position.
The sequence switch remains stationary during the time the air damper travels to its
closed position.
As soon as the signal contact for minimum air is operated by the actuator, the
sequence switch starts running again and continues with the burner's program
sequence, which can no longer be influenced from externally:
·
Preignition (3 seconds / 1.5 seconds with the LFE1.1)
·
Release of the first fuel value at terminal 5 (the fuel valve of a pilot burner, which
must be shut on completion of the second safety time, must be connected to
terminal 10)
·
Completion of the set safety time. If no flame is established during that period of
time, lockout will occur (always with interlocking of the burner control)
·
Following an interval of 11 seconds (5.5 seconds with the LFE1.1) of the first fuel
valve, the second fuel valve will be released
·
The pilot burner, if connected to terminal 10, will be shut
·
The load controller will be switched on following a further interval of 12 seconds (6
seconds with the LFE1.1). The burner's operating position has thus been reached.
From now on, the load controller controls the burner's output by increasing or
decreasing the fuel throughput and the air flow in response to the heat demand
(ratio control). This can be accomplished either in a stepwise fashion, e.g. with a
thermostat, or continuously by means of a modulating controller
Loss of flame during operation always leads to lockout.
In principle, the program sequence is the same as startup without ignition spark
supervision.
Exceptions:
·
If the UV flame detector does not receive an input signal during the preignition
time, lockout will occur before any gas is released, that is, safety time TSA = 0
seconds
·
With ignition spark supervision, the safety time for the pilot burner can only be
adjusted between 0...6 seconds (= TSA' in the sequence diagram of the sequence
switch)
9/19
CC1N7461en
21.08.2018
Advertisement
