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Dimensions
Section 10
Temperature derating
Multi 9
Miniature circuit
breakers
The maximum permissable current in a device depends on the ambient temperature
in which it is placed.
Ambient temperature is the temperature inside the enclosure or switchboard in which
the devices have been installed.
The reference temperature is in the coloured column for the various circuit-breakers.
When several simultaneously operating circuit-breakers are mounted side by side in a
small enclosure, the temperature rise inside the enclosure causes a reduction in the
current rating. A reduction cœffficient of the order of 0.8 must therefore be allocated
to the rating (already derated if it depends on the ambient temperature).
Example
The table below shows how to determine the following for a C60 depending on the
ambient temperature and the installation mode:
The service current which must not be exceeded for a rating of 20 A (reference
b
b
temperature 30 °C)
The ratings which must be adopted (in bold) to allow a service current of 20 A
b
b
Service current which must not be exceeded (A)
Installation
conditions
Single C60
Several C60a in the same enclosure
(calculed using the reduction
coefficient indicated below)
Temperature (°C)
30 °C
40 °C
30 °C
40 °C
nominal
real
real
real
real
rating (A)
rating (A)
rating (A)
rating (A)
rating (A)
C60
20
20
19
20 x 0.8 = 16
19 x 0.8 = 15.2
25
25
23.7
25 x 0.8 = 20
23.7 x 0.8 = 18.96
32
32
30.4
32 x 0.8 = 25.6 30 x 0.8 = 24
Max current (A) according to ambient temperature
Déclic, DPN, DPN N
Temperature (°C)
20 25 30 35 40 45 50 55 60
Rating (A)
1
1.04 1.02
1
0.98 0.96 0.93 0.91 0.89 0.86
2
2.08 2.04
2
1.96 1.91 1.87 1.82 1.77 1.72
3
3.16 3.08
3
2.92 2.83 2.75 2.66 2.57 2.47
6
6.26 6.13
6
5.87 5.73 5.60 5.45 5.31 5.16
10
10.5 10.3
10
9.73 9.45 9.17 8.87 8.57 8.25
16
16.7 16.4
16
15.6 16.2 14.8 14.4 14 13.5
20
20.9 20.4
20
19.5 19 18.7 18 17.5 17
25
26.1 25.5
25
24.4 23.8 23.3 22.7 22.1 21.4
32
33.6 32.8
32
31.2 30.3 29.4 28.5 27.6 26.7
40
42 41
40
39 37.9 36.8 35.7 34.6 33.4
C60H : curve B and C
Temperature (°C)
20 25 30 35 40 45 50 55 60
Rating (A)
1
1.05 1.02
1
0.98 0.95 0.93 0.90 0.88 0.85
2
2.08 2.04
2
1.96 1.92 1.88 1.84 1.80 1.74
3
3.18 3.09
3
2.91 2.82 2.70 2.61 2.49 2.37
4
4.24 4.12
4
3.88 3.76 3.64 3.52 3.36 3.24
6
6.24 6.12
6
5.88 5.76 5.64 5.52 5.40 5.30
10
10.6 10.3
10
9.70 9.30 9.00 8.60 8.20 7.80
16
16.8 16.5
16
15.5 15.2 14.7 14.2 13.8 13.3
20
21.0 20.6
20
19.4 19.0 18.4 17.8 17.4 16.8
25
26.2 25.7
25
24.2 23.7 23.0 22.2 21.5 20.7
32
33.5 32.9
32
31.4 30.4 29.8 28.4 28.2 27.5
40
42.0 41.2
40
38.8 38.0 36.8 35.6 34.4 33.2
50
52.5 51.5
50
48.5 47.4 45.5 44.0 42.5 40.5
63
66.2 64.9
63
61.1 58.0 56.7 54.2 51.7 49.2