Siemens Desigo TRA Mounting And Installation Manual page 11

. Mains and operating
voltage
. Caution with regard
to foreign voltages!
. Measures against
lightening
Mains filter
Siemens
Building Technologies
The following regulations apply to mains and operating voltage:
Item Regulations
Operating voltage It must meet requirements for SELV or PELV. Permitted
AC 24 V deviation for nominal voltage AC 24 V on the device: -10 - +
20%.
Transformer • Use safety insulating transformers as per EN 61558 with
specification
AC 24 V
• Power taken from the transformer should be at least 50%
• Transformer nominal power should be at least 25 VA. For
Operational Transformers on the secondary side correspond to the
voltage fuse actual load of all connected devices as per transformer
AC 24 V sizing:
– AC 24 V line (system potential) must always be fused.
– We required, an additional line ⊥ (system neutral).
Mains fuse Transformer, primary side:
Installation box fuse (control circuit fuse).
Any insertion or drawing of dangerous voltages to the system's low-voltage circuit,
e.g. caused by improper wiring directly places people at risk can may result in the
partial or complete destruction of the building automation and control system!
All wiring existing the building is at severe risk of over-voltage caused by
atmospheric discharges (lightening). Overvoltages can be inductively, capacitive or
galvanically into electronic systems and may cause faults or even destroy sensitive
components.
This overvoltage must be diverted to the earth to limit the damage. This may be
achieved with the help of gas-filled surge arrestors, varistors and diodes as well as
capacitors and chokes.
Specialized companies (e.g. Siemens, Phoenix) combines these elements into
protective components to provide optimum protection for various systems.
Spikes and high-frequency interference may occur in areas with high levels of
interference. The disturbances not only impact the transformer on the primary side,
but may also influence secondary connected components.
A mains filter should be attached on the primary transformer if such interference is
anticipated. Mains filters should be installed as close to the network transformer as
possible and grounded.
Mounting and installation
Important information on safety
double insulation designed for 100% duty to supply
SELV or PELV circuits..
of nominal load for efficiency reasons (effectiveness).
smaller transformers, the ratio of open circuit voltage to
full load is unfavorable
(> + 20%).
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CM111043en_03
2013-02-23