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SIEMENS LOK16.. / LGK16.. CONTROL BOX
Control boxes type LOK16... / LGK16... feature a self-checking flame supervision cir-
cuit. The supervision circuit initiates the required safety actions not only in the case
of premature or missing flame signals, but also in the event of any kind of fault on the
flame detector, the detector cables or the flame signal amplifier that could simulate a
flame signal during burner operation.
The burner controls are therefore suited for use in all types of oil- or gas-fired com-
bustion plant where self-checking flame supervision systems are either mandatory
or recommended:
Burners that operate continuously
Burners in intermittent operation that, in the case of great heat demand, may
operate continuously for more than 14 hours, e.g. in plant using boiler sequen-
cing
Burners that need to comply with the German TRD 411 and TRD 412 regulations
for steam boilers
Burners in plant where, for specific safety requirements, supervision of the bur-
ner by a self-checking flame supervision system seems advisable.
The control sequence and connection circuitry of the LOK16... / LGK16... burner
controls are identical to those of the LAL2... and LFL1... respectively (with the excep-
tion of the LFL1.148), so that existing combustion plant can also be equipped with
self-checking burner controls:
provided very good flame detector current values are measured in the plant
supervised so far by the LFL1..., and
provided the following types of flame detectors are either installed or can subse-
quently be fitted:
- Flame supervision when using LOK16:
Selenium photocell detector RAR..
- Flame supervision when using LGK16:
Flame detector QRA53.. / QRA55..
Ionization probe
Flame detector QRA53... / QRA55... together with ionization probe, e.g. in the
case of burners using a pilot burner.
WARNING NOTES
To avoid injury to persons, damage to property or the environment, the following
warning notes should be observed!
Do not open, interfere with or modify the unit!
All activities (mounting, installation and service work, etc.) must be performed by
qualified staff
Before performing any wiring changes in the connection area of the LOK16... /
LGK16..., completely isolate the burner control from the mains supply (all-polar
disconnection)
Ensure protection against electric shock hazard by providing adequate protec-
tion for the burner control's connection terminals
Check to ensure that wiring is in an orderly state
Press the lockout reset button only manually (applying a force of no more than
10 N) without using any tools or pointed objects
Do not press the lockout reset button on the unit or the remote reset button (input
21) for more than 10 seconds, since this would damage the lockout relay inside
the unit
Fall or shock can adversely affect the safety functions. Such units must not be
put into operation, even if they do not exhibit any damage
Installation notes
Always run the high-voltage ignition cables separately while observing the grea-
test possible distance to the unit and to other cables
Neutral conductors must not be interchanged
Commissioning notes
Prior to commissioning, check to ensure that wiring is in an orderly state.
When commissioning the plant or when doing maintenance work, make the following
safety checks
Safety check
Burner startup with flame detector
darkened
Burner startup with simulated
flame
Burner operation with simulated
loss of flame; for that purpose,
darken the flame detector in
operation and leave it in that state
Burner startup with response of
air pressure switch
Burner operation with simulated
air pressure failure
Principle of self-supervision
In contrast to conventional amplifiers, the signal delivered by the flame
detector is handled dynamically and not statically. The flame detector
signal is converted to a sequence of control pulses and then fed to the
flame relay circuit. The latter is designed such that the flame relay can
only be energized by a flame signal of the described form. If the pulses
change due to a faulty detector or faulty detector cables, the relay will be
deenergized and the burner control triggers the required safety actions. In
the case of UV supervision, it must also be ensured that self-ignition of
the UV tube (e.g. due to aging) does not simulate a flame signal. For that
reason, incident radiation at the UV cell is periodically interrupted by a
shutter. In addition to the self-checking facility, the flame signal circuit is
subjected to a functional test during the prepurge time. If it does not ope-
rate correctly, the startup sequence will be aborted or lockout initiated.
Furthermore, if mains voltage drops to a level where safe operation of the
Anticipated response
Lockout at the end of «TSA»
Lockout after no more than 40 seconds
- LOK16... with wire link cut: Start repetition
followed by lockout at the end of «TSA»
- LGK16... and LOK16... with wire link closed:
Immediate lockout
Prevention of startup / lockout during «t1»
Immediate lockout
burner control is no longer ensured, the burner will automatically shut
down. When mains voltage returns to the normal level, the burner control
repeats the startup sequence. If the detector signals are only slightly
above the minimum levels, such mains voltage fluctuations can also give
rise to burner lockout however.
Prerequisites for burner startup:
The burner control is reset and in the start position (terminals 11 and 12 must
receive power)
The air damper is closed. End switch «z» for the fully closed position must feed
power from terminal 11 to terminal 8
All control contacts between terminals 12 and 5 (limit thermostat, control thermo-
stat, etc.) must be closed
A Start: When «R» closes, the control box sequence switch starts running. At the
same time, the fan motor connected to terminal 6 (only prepurging) receives power
and, on completion of «t7», the fan motor or flue gas fan at terminal 7 (pre- and
postpurging) also receives power. On completion of «t16», the control command to
open the air damper is given via terminal 9. During the running time of the motor, the
sequence switch does not operate, as terminal 8, via which the motor of the
sequence switch first receives power, is not live during that period of time. The
sequence switch starts again and programs only after the air damper is fully open
and end switch «a» has changed over to feed power to terminal 8.
t1 Prepurge time with air damper fully open (nominal amount of combustion air)
Shortly after the start of the prepurge time, air pressure switch «LP» must change
over, thus interrupting the current path between terminals 4 and 13. Otherwise, the
burner control would go to lockout (start of air pressure check). At the same time,
terminal 14 must be live since this current path is used to power the ignition transfor-
mer and the fuel valves.
t3´ With the LOK16..., an ignition transformer connected to term nal 15 is therefore
switched on at this point in time (long preignition). If there is no «LP», the ignition
transformer receives power already with the start command. On completion of the
prepurge time, the burner control via terminal 10 drives the air damper into the low-
fire position, which is determined by the changeover point of auxiliary switch «m».
During the positioning time, the sequence switch stops again until terminal 8 recei-
ves power from «m».
t5 Interval On completion of «t5», terminal 20 receives power. At the same time,
control outputs 9 to 11 and input 8 are galvanically separated from the unit's control
section, so that the latter is protected against reverse voltages from the load control
circuit. The startup sequence of the burner control ends with the release of load con-
troller «LR» at terminal 20. The sequence switch switches itself automatically off,
depending on the time variant used, either immediately or after some so-called «idle
steps», that is, without changing the contact positions.
t3 Short preignition time; followed by fuel release via terminal 18.
TSA Safety time (part load) On completion of the safety time latest, a flame signal
must be present at the input of the flame signal amplifier, or else the burner control
will initiate lockout.
Only with LOK16...: t3n Postignition time (provided the ignition transformer is
connected to terminal 15).
t4 Interval until the fuel valve is released via terminal 19.
(Burners using a pilot burner)
t3 / t3´ Short preignition time; followed by release of fuel for the pilot burner via ter-
minal
17.
TSA / TSA´ First safety time (ignition load) On completion of the safety time latest,
a flame signal must be present at the input of the flame signal amplifier, or else the
burner control will initiate lockout.
t4 / t4´ Interval until the fuel valve at terminal 19 is released (start load of the main
burner).
Times «TSA´», «t3´» and «t4´» are only programmed by burner controls type
LGK16.335... and LGK16.635...
t9 Second safety time: On completion of the safety time, the main burner must
have been ignited by the pilot burner, since the pilot gas valve is closed on comple-
tion of «t9».
B Operating position of the burner
B-C Burner operation (generation of heat) During burner operation, the load con-
troller drives the air damper to the nominal load or low-fire position, depending on
heat demand. Here, the nominal load is released by auxiliary switch «v» in the air
damper actuator.
C Controlled shutdown by «R» In the case of controlled shutdown, the fuel valves
are immediately closed and, at the same time, the sequence switch starts again to
program the postpurge time.
t6 Postpurge time (postpurging with fan «M2» connected to terminal 7). Shortly
after the start of the postpurge time, voltage at terminal 10 is reinstated, so that the
air damper is driven into the «MIN» position. The full closing of the air damper starts
only shortly before the completion of the postpurge time initiated by the control
signal on terminal 11, which also remains live during the following burner off period.
t13 Permissible afterburn time During «t13», the flame signal input may still
receive a flame signal -> No lockout
D-A End of control sequence (= start position) When, on completion of «t6», the
sequence switch has reset the control contacts to their start positions, thereby
switching itself off, the detector and flame simulation test is started again. However,
during the burner off period, lockout can occur only if the faulty flame signal lasts a
few seconds. Hence, short ignition pulses of the UV
detector caused by cosmic radiation do not initiate lockout.
Control sequence in the event of fault and indication of lockout
In case of any disturbance, the supply of fuel will immediately be interrupted. At the
same time, the sequence switch stops and thus the lockout indicator also. The
symbol appearing above the reading mark indicates the kind of fault:
No start, because one of the contacts is not closed (also refer to «Prerequisites
for burner startup») or lockout during or after completion of the control
sequence due to extraneous light (e.g. flame not extinguished, leaking fuel valves,
faulty flame supervision circuit, or similar).
Abortion of startup sequence, because end switch «a» has not fed the OPEN
signal to terminal 8. Terminals 6, 7 and 14 and, in case LOK16... is used, termi-
nal 15,also remain live until the fault is corrected.
P
Lockout, because the air pressure signal has not been received at the start of
the air pressure check.
Lockout due to a fault in the flame supervision circuit.
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