Safety notes - Basic Documentation - GDB181.1E/BA - GDB181.1EMBA - GLB181.1E/BA

VAV Compact Controller BACnet MS/TP G..B181.1E/BA

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Damper actuators
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Technical Documentation > Basic Documentation
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This section contains general regulations and the regulations for mains and operating voltage. It also provides important information regarding your own safety and that of the entire plant.

Safety note

The warning triangle to the left means that observance of all relevant regulations and notes is mandatory. If ignored, injury to persons or damage to property may result.


Observe the following regulations during engineering and project execution:

  • Electrical and high-voltage directives of the respective country

  • Other country-specific regulations

  • House installation regulations of the respective country

  • Regulations issued by the utility

  • Diagrams, cable lists, disposition drawings, specifications and instructions as per the customer or the contractor in charge

  • Third-party regulations issued by general contractors or building operators


The electrical safety of building automation and control systems supplied by Siemens depends primarily on the use of extra low-voltage with safe isolation from mains voltage.


Depending on the type of extra low-voltage earthing, a distinction is to be made between SELV and PELV as per HD 384, “Electrical plants in buildings“:

Unearthed = SELV (Safety Extra Low Voltage)

Earthed = PELV (Protective Extra Low Voltage)

Earthing of
G0 (system neutral)

Observe the following for grounding G0:

As a rule, earthing and non-earthing of G0 is permissible for AC 24 V operating voltage. Decisive are the local regulations and customary procedures. For functional reasons, earthing may be required or not permissible.

Recommendation on
earthing G0

AC 24 V systems should always be earthed if this does not contradict the manufacturer’s specification.

To avoid earth loops, systems with PELV may only be earthed at one point of the system, normally by the transformer, unless otherwise specified.

Operating voltage
AC 24 V

With regard to AC 24 V operating voltage, the following regulations must be complied with:


Operating voltage

AC 24 V

The operating voltage must comply with the requirements for SELV or PELV:

  • Permissible deviation of AC 24 V nominal voltage at the actuators: +/–20 %

Specification on AC 24 V transformers
  • Safety isolating transformers as per EN 61558, with double insulation, designed for 100 % on time to power SELV or PELV circuits

  • 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
AC 24 V operating voltage

Secondary side of transformer:

  • According to the effective load of all connected devices

  • Line G (system potential) must always be fused

  • Where required, line G0 (system neutral) also