Flame Detector Qra2 / Qra4 / Qra10 - Siemens LME7 Series Manual

Measuring circuit for detector
current measurement
Building Technologies

4.12.2 Flame detector QRA2 / QRA4 / QRA10

Caution!
If flame detectors QRA2 / QRA4 / QRA10 are used for flame supervision with the
LME7, it must be ensured that the burner control is permanently connected to
power (conforming to EN 298), thus enabling the system to detect flame
detector failures during startup and shutdown.
Generally, the system works with QRA flame detectors in intermittent operation.
If this is not observed, there is a risk of loss of safety functions.
Technical Data see Data Sheet N7712, flame detector QRA2 / QRA10!
Technical Data see Data Sheet N7711, 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
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 ς
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 LME basic
unit must always be connected to mains supply. If this is not observed, the
safety functions may be 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
33/106
CC1P7105enr
17.04.2018