Configuring
4.7 Selection and installation of cabinets
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
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4.7 Selection and installation of cabinets
Reasons for installing an S7-300 in a cabinet
Your S7-300 should be installed in a cabinet,
• if you plan a larger system,
• if you are using your S7-300 systems in an environment subject to interference or
contamination, and
• to meet UL/CSA requirements for cabinet installation.
Selecting and dimensioning cabinets
Take the following criteria into account:
• ambient conditions at the cabinet's place of installation
• the specified mounting clearance for racks (mounting rails)
• accumulated power loss of all components in the cabinet.
The ambient conditions (temperature, humidity, dust, chemical influence, explosion hazard)
at the cabinet's place of installation determine the degree of protection (IP xx) required for
the cabinet.
Reference for degrees of protection
For further information on the degrees of protection, refer to IEC 529 and DIN 40050.
The power dissipation capability of cabinets
The power dissipation capability of a cabinet depends on its type, ambient temperature and
on the internal arrangement of devices.
Reference for power loss
For detailed information on power dissipation, refer to the Siemens catalogs NV21 and ET1.
Specification of cabinet dimensions
Note the following specifications when you determine the dimensions of a cabinet for your
S7-300 installation:
• Space required for racks (mounting rails)
• Minimum clearance between the racks and cabinet walls
• Minimum clearance between the racks
• Space required for cable ducts or fan assemblies
• Position of the stays
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