Installation Notes; Electrical Connection Of Flame Detectors - Siemens LME11 series Manual

Installation notes

Electrical connection of flame detectors

Building Technologies
HVAC Products
•
Always run the ignition cables separate from the unit and other cables while ob-
serving the greatest possible distance
•
Do not mix up live and neutral conductors
•
Install switches, fuses, earthing, etc., in compliance with local regulations
•
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
•
Make certain that the maximum permissible current rating of the connection termi-
nals will not be exceeded
•
Do not feed external mains voltage to the control outputs of the unit. When testing
the devices controlled by the burner control (fuel valves, etc.), the LME... must not
be connected
•
In the case of burners with no fan motor, an AGK25 must be connected to terminal
3 of the unit, or else the burner cannot reliably be started up
•
For safety reasons, feed the neutral conductor to terminal 2. Connect the burner
components (fan, ignition transformer and gas valves) to the neutral distributor as
shown below in figure 7101a05. The connection between neutral conductor and
terminal 2 is prewired in the base
Example
2 3 7
Z
M
N
7101a05/0804
Wiring of neutral conductors!
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 is 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
•
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
•
Earth the burner in compliance with the relevant regulations; earthing the boiler
alone does not suffice
4 5
BV2
BV1
Legend
BV... Fuel valve
M Fan motor
Z Ignition transformer
3/23
CC1N7101en
29.06.2006