Siemens S5-135U/155U - Manual (Page 60)

3-34
System Manual
C79000-G8576-C199-06
3.7.1 Types of Cabinet
The following table provides on overview of the most common types of
cabinet. It also shows the principle of heat removal, as well as the estimated,
maximum achievable power loss removal and the type of protection* .
Open Cabinets Closed Cabinets
Through-ventilation by
natural convection Increased
through-ventilation Natural convection Forced circulation
using fan assembly,
enhanced natural
convection Forced circulation
using heat exchanger,
external ventilation
inside and outside
Heat removal primarily
by natural thermal
convection, small
portion via the cabinet
wall Increased heat removal
through increased air
movement Heat removal only
through the cabinet
wall; only low power
dissipation permissible.
Heat accumulation
usually occurs in the
top of the cabinet. Heat removal only via
the cabinet wall. Forced
ventilation of the
internal air results in
improved heat removal
and prevention of heat
accumulation. Heat removal through
exchange between
heated internal air and
cool outside air. The
increased surface of the
folded-area sectional
wall of the heat
exchanger and forced
circulation of internal
and external air permit
good heat output.
Type of protect. IP 20 Type of protect. IP 20 Type of protect. IP 54 Type of protect. IP 54 Type of protect. IP 54
Typical removable power dissipation under the following boundary conditions:
S
Cabinet size 2200 x 600 x 600 mm
S
Temperature difference between external and internal temperature of the cabinet: 20
°
C**
Up to 700 W Up to 2700 W (1400 W
with very fine filter) Up to 260 W Up to 360 W Up to 1700 W
* The location and ambient conditions are decisive for selection of the type of cabinet protection
(
Õ see IEC 529 and DIN 40050).
** For other temperature differences, refer to the temperature characteristics of the cabinet
manufacturer.
3.7.2 Clearances in Cabinets
You must first define the components to be fitted in the cabinet. Then
calculate the total power dissipation of the individual components. The
following stipulations must be observed:
S
The expansion units can be accommodated with the respective central
controller in one cabinet, or in two or more cabinets (centralized or
distributed).
S
On account of the required clearances and maximum permissible
installation height for control elements, a maximum of three SIMATIC S5
devices can be arranged one above the other.
Installation Guidelines