Siemens LGA52.150B27 - Internal diagram LGA41...

12/15
Building Technologies Division CC1N7418en
21.06.2016
Function (cont´d)
When the switch-on command is given, power is supplied to the ignition transformer
and the heating coil of the bimetal sequencing device. The bimetal bends and pushes
contact set «c, d, e» towards «f». On completion of the preignition time, the system tilts
so that «e - f» closes and «f - g» opens, «BV1» receives voltage. Contacts «c - d» still
remain closed («c» resting on «d»). On flame establishment, the flame relay is
energized, latching mechanically «e - f» in the position now assumed. The relay also
closes contact «f» and, at the same time, opens «c - d», so that the ignition transformer
and the bimetal heating element will be switched off. Then, «d» slowly returns to its
starting position, also catching «g». When tilting back, «g - f» closes, so that the main
valve «BV2» will be energized.
If no flame signal is generated, the flame relay does not open «c - d», so that the
bimetal will continue to be heated. The bimetal thus continues to bend until – tilting – it
actuates contact «tz2»:  Lockout.
In the event of an erroneous premature flame signal, the flame relay – by means of its
latch – prevents «e - f» from making, which means no release of fuel. «TZ», however,
still receives power so that the bimetal continues to bend until, eventually; lockout is
initiated by «tz2».
EK
1
SB
W
R
L
N
210
AL
9
11
83 76
45
12
Z BV1
BV2
ION
7418i02/0304
LGA41...
L1
tz2
X
Y
Z
a
b
fr
TZ
c
d
e
tz1
f
g
FR
Si
H
AL Fault status signal R Thermostat or pressurestat
BV... Fuel valve SB Safety limit thermostat
EK Lockout reset button Si External primary fuse
ION Ionization probe TZ Electro-thermal timer
FR Flame relay (bimetal system) with contacts «tz»
L1 Built-in lockout warning lamp W
Limit thermostat / pressure switch
H Main switch Z Ignition transformer
Internal diagram
LGA41...
Legend