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Building Technologies Division
Basic documentation LMV36...
CC1P7544en
Infrastructure & Citiies Sector
4 Technical data
25.09.2013
4.4.3 Photoresistive flame detectors QRB…
No-load voltage at QRB... terminal
(X10–05 pin 3)
Approx. DC 5 V
Max. perm. length of QRB... detector
cable (laid separately)
3 m (wire – wire 100 pF/m)
Note
A detector resistance of RF <500
is identified as a short-circuit and leads to safety
shutdown in operation as if the flame had been lost.
For this reason, before considering the use of a highly sensitive photoresistive detector
(QRB1B... or QRB3S), it should be checked whether this type of flame detector is
indeed required! Increased line capacitance between QRB... connection and mains live
wire
L
has an adverse effect on the sensitivity and increases the risk of damaged flame
detectors due to overvoltage. Always run detector cables separately!
Threshold values when flame is supervised by QRB...:
Start prevention (extraneous light)
with
R
QRB
<400 k
Intensity of flame
≥
10%
Operation with
R
QRB
<230 k
Intensity of flame >16%
Short-circuit detection with
R
QRB
<0.5 k
0,1 1 10 100 1000
7540d04
e/
1010
Figure 11: QRB… input at AC 120 V
A flame detector resistance of RF <500
Ω
is identified as a short-circuit and leads to
safety shutdown in operation, like in the case of loss of flame.