Electrical Connection Of Flame Detectors; Commissioning Notes - Siemens LGB21.130A17 Datasheet

Electrical connection of flame detectors

Commissioning notes

Building Technologies
HVAC Products
It is important to achieve practically disturbance- and loss-free signal transmission:
•
Never run detector cables together with other cables
– Line capacitance reduces the magnitude of the flame signal
– Use a separate cable
•
Observe the permissible length of the detector cables (refer to «Technical data»)
•
The ionization probe and the ignition electrode are not protected against electric shock
hazard
•
Locate the high-voltage ignition electrode and the ionization probe such that the ignition
spark cannot arc over to the ionization probe (risk of electrical overloads) and that it
cannot adversely affect the supervision of ionization
•
With both ionization current and UV supervision, the cable length for flame detec-
tion must not exceed 20 m
•
Insulation resistance
– Must be a minimum of 50 MΩ between ionization probe and ground
– Soiled detector holders reduce the insulation resistance, thus supporting cree-
page currents
– Prerequisite is not only high-quality heat-resistant insulation of the probe's
cable, but also of the ionization probe itself (ceramic holder)
•
Earth the burner in compliance with the relevant regulations; earthing the boiler
alone does not suffice
•
The connection diagrams show the burner controls with earthed neutral conductor. In
networks with nonearthed neutral conductor and ionization current supervision, terminal
2 must be connected to the earth conductor via an RC unit (type reference
ARC 4 668 9066 0). It must be made certain that local regulations are complied with
(e.g. protection against electric shock hazard) since AC 230 V / 50 Hz mains voltage
produces peak leakage currents of 2.7 mA
•
When commissioning the plant for the first time or when doing maintenance work,
make the following safety checks:
Safety check to be carried out
a) Burner startup with previously inter-
rupted line to the ionization probe and
flame detector darkened in the case of
QRA... or QRC1...
b) Burner operation with simulated loss of
flame. For that purpose, cut off the gas
supply (e.g. disconnect the fuel valve
while ensuring protection against elec-
tric shock hazard)
c) Burner operation with simulated air
pressure failure (not with atmospheric
burners)
Anticipated response
Lockout at the end of «TSA»
Immediate lockout
Immediate lockout
CC1N7435en
3/22
11.01.2007