Siemens SQN72 Series - Page 19

19/20
Smart Infrastructure CC1N7802en
8/11/2021
Key
A Designation for internal circuit.
Appears in the second
position after the period in the type reference
I/II
End switch
es
III/IV/V
Auxiliary switch
es
AL
Remote lockout display (alarm)
BV1
Fuel valve stage 1
BV2
Fuel valve stage 2
BV3
Fuel valve s
tage 3
EK2
Exter
n
al remote
lockout reset button
ION
Ionization
probe
F
Internal fuse, not replaceable
FS
Flame signal
GP
Gas pressure switch
HS
Main switch
KL
Low
-
fire
L
Phase
LK
Air damper
LKP
Air damper position
LP
Air pressure switch
L
R
Load
controller
M
Bu
r
ner motor
or fan motor
M
Actuator synchronous motor
M1
Without postpurging
M2
With postpurging
N
Neutral conductor
NL
High
-
fire
OH
Oil preheater
OW
Oil preheater release contact
QRB
Photoresistive dete
ctor
R
Control t
h
ermostat
o
r pressurestat
Relay
R
V
Control valve
SA
Actuator
Si
External primary fuse, as specified in the data sheet of the relevant burner control
S
B
Safety limiter
STx
Stage
tx / Tx
Program times (r
efer to the data
s
heet of t
h
e relevant burner control)
TSA
Safe
ty time
R
Resistor
Z
Ignition transformer
CLOSED
Damper closed

Direction of rotation OPEN

Direction of rotation CLOSED
Program sequence
–
Diagrams
A
Burner ON
A
–
B
Bu
r
ner star
t
u
p
B
–
C
Burner operation / load con
trol operation, modulating or 2
-
stage
C
Burner OFF
C
–
D
Postpurge time
D
End of program sequence, burner control ready for restart
Control signals delivere
d by burner control
Required inp
ut signals
Permissible input signals