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Operating voltage
AC 24 V
Device safety
Electrical parallel
connection
KNX bus powering
Note
Warning,
maintenance
38 / 44
Siemens
Building Technologies
With regard to AC 24 V operating voltage, the following regulations must be
complied with:
Regulation
Operating
The operating voltage must comply with the requirements for
voltage
SELV or PELV:
∂ Permissible deviation of AC 24 V nominal voltage at the
AC 24 V
actuators: +/–20 %
∂ Safety isolating transformers as per EN 61558, with double
Specification
insulation, designed for 100 % on time to power SELV or
on AC 24 V
PELV circuits
transformers
∂ Determine the transformer's output by adding up the power
consumption in VA of all actuators used
∂ For efficiency reasons, the power drawn from the transformer
should amount to at least 50 % of the nominal load
∂ The transformer's nominal capacity must be at least 25 VA.
With smaller transformers, the ratio of no-load voltage and full
load voltage becomes unfavorable (> + 20 %)
Fusing of
Secondary side of transformer:
AC 24 V
∂ According to the effective load of all connected devices
operating
∂ Line G (system potential) must always be fused
voltage
∂ Where required, line G0 (system neutral) also
7.2
Device-specific regulations
Among other aspects, the safety of devices is ensured by extra low-voltage power
supply (AC 24 V) as per SELV or PELV.
Electrical parallel connection of VAV compact controllers is possible, provided the
required operating voltage tolerance is observed. The voltage drops of the
supply lines must be taken into consideration.
When planning and installing room controllers and field devices with KNX bus
connection, the permissible cable lengths, power supply and topologies have to be
followed. Planning should take into account possible future extensions of a plant.
Mechanical coupling of the devices is not permitted.
Do not open the actuator!
The device is maintenance-free. Only the manufacturer may carry out any repair
work.
VAV compact controller KNX/PL-Link G..B181.1E/KN
CE1P3547en
2017-03-23
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