Engineering Guide CDA3000
7-3
7 System installation
DE
EN
1
2
3
4
5
6
7
A
α
ι
and
α
α
designate the heat transfer coefficients for the inner and outer
wall respectively;
λ
designates the heat transfer coefficient of the wall
material and s the wall thickness.
Heat transfer resistance of the switch cabinet.
7.1.2 Effective switch
cabinet surface
Of the variables cited above, the effective switch cabinet surface A
requires a special note of explanation: The heat output emitted from the
switch cabinet is not only dependent on its actual surface area; the mode
of installation of the cabinet is also decisive. A housing standing free and
open on all sides can emit more heat than one mounted on a wall or in a
niche. For that reason there are precise regulations as to how the effec-
tive switch cabinet surface is to be calculated dependent on the mode of
installation. The formulae to calculate A are laid down in DIN 57660 Part
500 / VDE 0660 DIN 500 (See Figure 7.1).
Figure 7.1
Calculation of the effective emitting switch cabinet surface
R
l
k
---
m
2
K
W
----------
=
Enclosure installation type to VDE 0660 Part 500
Single enclosure, all-round, freestanding
Single enclosure for wall mounting
Start or end enclosure, freestanding
Start or end enclosure for wall mounting
Middle enclosure for wall mounting,
Middle enclosure, freestanding
Middle enclosure for wall mounting,
covered roof areas
Installation type
to VDE 0660/500
Formula for calculation of A [m
2
]
A = 1.8 x H x (W+D) + 1.4 x W x D
A = 1.4 x B x (H+D) + 1.8 x D x H
A = 1.4 x T x (H+W) + 1.8 x W x H
A = 1.4 x H x (W+D) + 1.4 x W x D
A = 1.8 x W x H + 1.4 x W x D + D x H
A = 1.4 x W x (H+D) + D x H
A = 1.4 x W x H + 0.7 x W x D + D x H
W = Cabinet width [m] H = Cabinet height [m] D = Cabinet depth [m]
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