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Building Technologies Basic Documentation LMV27... CC1P7541en
4 Technical Data 17.12.2018
4.4.3 Photoresistive flame detectors QRB1 / QRB3
No-load voltage at QRB1/QRB3 terminal
(X10-05 pin 3)
Approx. DC 5 V
Max. perm. length of QRB1/QRB3
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 QRB1/QRB3 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 QRB1/QRB3:
Start prevention (extraneous light)
with R
QRB
<400 k
Intensity of flame ≥10%
Operation with RQRB
<230 k
Intensity of flame >16%
Short-circuit detection with RQRB
<0.5 k
0,1 1 10 100 1000
Bild 462en/0718
Figure 8: QRB1/QRB3 input at AC 230 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.
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