User's Manual

Siemens PLT 111 · 1999
3/25
Automation systems
Standard cabinets
Permissible thermal loading
Permissible thermal loading, configuring guidelines
Standard cabinets without forced ventilation
Basic and extension units fitted in standard cabinets can be
operated without fans if
• the cabinet thermal load P
s max
permissible depending on the
cabinet unit temperature is not exceeded and
• a heat loss greater than 150 W does not occur in any extension
system.
If many I/O modules are used with a high heat loss, these should
not all be fitted next to one another but distributed amongst the
various subracks in order to prevent heat accumulation. P
s max
is usually not achieved in the extension cabinet even with the full
configuration of 42 I/O modules. An exact determination of the
total heat loss is only required with a non-typical module config-
uration (many I/O modules of the same type, modules with more
than 8 W heat loss).
Standard cabinets with degree of protection IP 20, with
forced ventilation
Extension unit with > 150 W/subrack
Basic and extension cabinets whose thermal load (without fan
subassembly) is not exceeded must be provided with forced
ventilation if an extension unit is configured with I/O modules
such that the heat loss of this subrack exceeds 150 W. At least
one fan subassembly must then be provided between the basic
unit GE and the 1st extension unit EE1 (in the basic cabinet) or
between the 4th and 5th extension units (in the extension cabi-
net).
Cabinet thermal load > 350 to 450 W, < 700 W
If the thermal load is between 350/450 W (depending on cabinet
ambient temperature) and 700 W, and if 150 W is not exceeded
in any extension unit of the cabinet, at least one fan subassem-
bly must be provided between the basic unit GE and the 1st
extension unit EE1 (in the basic cabinet) or between the 4th and
5th extension units (in the extension cabinet).
A 2nd fan subassembly must be provided if an extension unit is
additionally configured with I/O modules such that its heat loss
exceeds 150 W. The 2nd fan subassembly must be fitted above
the 3rd extension unit EE3 (in the basic cabinet) or above the
6th extension unit EE6 (AS 235, extension cabinet) or above the
7th extension unit EE7 (AS 235 H, extension cabinet).
Standard cabinet with heat exchanger
The standard cabinet with heat exchanger can be operated
without an additional fan subassembly if the total thermal load of
350/450 W (depending on cabinet ambient temperature) is not
exceeded in the cabinet and if 150 W is not exceeded in any
extension unit.
The standard cabinet with heat exchanger is operated with a fan
subassembly if the total thermal load is < 700 W and if 150 W is
not exceeded in any extension unit. The fan subassembly must
be fitted between the basic unit and the 1st extension unit EE1
(in the basic cabinet) or between the 4th and 5th extension units
EE4 and EE5 (in the extension cabinet).
If the thermal load in one of the three extension units exceeds
150 W or if the total thermal load exceeds 700 W, a 2nd fan sub-
assembly must be fitted between the 2nd and 3rd extension
units EE2 and EE3 (in the basic cabinet) or between the 5th and
6th extension units EE5 and EE6 (AS 235, extension cabinet) or
between the 6th and 7th extension units (AS 235, extension cab-
inet). A maximum thermal load of 1000 W is then permissible.
Configuring values for thermal load
AS 235
Basic cabinet
without I/O modules,
redundant bus connection
≤ 150 W
Bus connection, single
- 10 W
Connected extension cabinet
+ 16 W
AS 235 extension cabinet without I/O
modules
0 W
AS 235 H
Basic cabinet
without I/O modules,
redundant bus connection
≤ 200 W
Bus connection, single
- 10 W
Connected extension cabinet
+ 8 W
AS 235 H extension cabinet without
I/O modules
30 W
This catalog is out of date, see note on page 1