10/22
Building Technologies
CC1N7435en
HVAC Products
11.01.2007
Flame supervision with UV detector QRA... and auxiliary unit AGQ... for LGB21... / LGB22... / LGB41...
Universal flame detector for use with gas and gas / oil burners. Incidence of light from
the front and laterally, total length 97 mm. Available with normal or, as QRA2M, with
higher sensitivity. Secured with flange and clamp. Also available as a metal encapsu-
lated version in the form of the QRA10... (for details, refer to Data Sheet N7712).
A special UV auxiliary unit AGQ1...A27 is required in connection with LGB... burner
controls.
That unit is to be connected to the mains supply via 2 cables, and to the burner control
via terminals 1, 2 and 11.
Using circuitry (A) or (B), there are 2 ways to make the quench test on aging UV detec-
tors and to detect UV light:
1. (A) Operation with a permanent line:
UV test at a higher supply voltage across the UV cell on startup and after con-
trolled shutdown.
2. (B) Operation with a controlled line:
UV test at a higher supply voltage only on startup, that is, during the interval
between controlled startup and air pressure signal.
– No voltage at the UV cell after controlled shutdown
– No full substitute for mode (A) above, since an aged UV cell can regenerate
itself
Measuring circuit
Connection diagram
12
2
11
*
1
74
3
5
a1
9
/0
3
0
1
br
bl rt
sw
AGQ1...A27
sw
bl
(B)
LGB...
QR
A
12
2
11
*
1
7435
a1
5/
0
7
0
4
GP/SB
R/W
L
L
N
QRA
+
-
br
bl rt
sw
AGQ1...A27
sw
bl
(B)
(A)
LGB...
Measurement made on the flame detector
GP Gas
pressure
switch
R
Temperature or pressure controller
SB
Safety limit thermostat
W
Limit thermostat or pressure switch
*
With LGB41...: Terminal 3
(A)
Operation with permanent line
(B)
Operation with controlled line
UV detector QRA...
Auxiliary unit
AGQ1...A27
Legend
