Qra2 / Qra4 / Qra10 (Lme71 / Lme73 Only) - Siemens LME71 Series Basic Documentation

Connection diagram
Measuring circuit for detector
current measurement
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4.12.2 QRA2 / QRA4 / QRA10 (LME71 / LME73 only)

Caution!
If QRA2-UV tubes, QRA4-UV tubes, or QRA10-UV tubes are used for flame
supervision on the LME7, it must be ensured that the burner control is
permanently connected to power (EN 298), thus enabling the system to detect
detector failures during startup and shutdown. The system generally operates
with QRA flame detectors in intermittent operation. Failure to observe this
information poses a risk of the safety functions being impaired.
For Technical data, refer to Data Sheet N7712, UV flame detector QRA2 /
QRA10!
For Technical Data, refer to Data Sheet N7711, UV flame detector QRA4!
Threshold values when flame is supervised by QRA
- Start prevention (extraneous light)
- Operation
Operating voltage
Mains frequency
Required detector current
Possible detector current during operation
Perm. length of detector cable
(normal cable, laid separately) ¹)
¹)
Multicore cable not permitted
Parameters Function
954 Flame intensity
1
2
Flame detector QRA
QRA...
Figure 5: Measuring circuit for QRA
Legend
A Exposure to light
C Electrolytic condenser 100...470 µF; DC 10...25 V
Microammeter Ri max. 5,000 
M
Warning!

Input QRA is not short-circuit-proof!
Short-circuits of terminal X10-06 pin 2 against earth can destroy the QRA
input

Simultaneous operation of flame detector QRA and ionization probe is not
permitted. If not observed, there is a risk of impairment of safety functions.

To ensure that the age of the UV tubes can be determined, the LME7 must
always be connected to mains voltage. Failure to observe this information
poses a risk of the safety functions being impaired
Basic Documentation LME7...
4 Technical data
Intensity (parameter 954) approx. 12%
Intensity (parameter 954) approx. 13%
AC 280 V ±15%
50...60 Hz 6%
Min. 70 µA
Max. 700 µA
Max. 100 m, unshielded
LME...
QRA -
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24.07.2020