14
System
pro M compact ®
Miniature circuit-breakers
S 200/S 200 M series
The influence of ambient temperature and interdependencies in the case of even loads on the load
capability of MCBs
Practical Note: This practical deduction, that is applicable for all types of characteristics, can be recommended for standard
environments. Selection criteria for rated current of circuit-breakers according to EN 60898 and EN 60947-2.
Choose the circuit-breaker that is appropriate for the lower of the rated value of the device or the permissible current loading.
Now, the major factors having an influence on the circuit-breaker, must be taken into account:
1. ambient temperature with IB 0.9 x In at 40 °C ambient temperature
2. mutual influence with IB 0.75 x In in the case of more than one circuit-breaker being loaded evenly in parallel.
The ensuing rated current of the circuit breaker is thus: In = 1.5 x rated current
Example: operating currect 4 A, then the rated current of the circuit-breaker is: In = 1.5 x 4 A = 6 A
The above takes into account all relevant factors and the circuit is protected at the lowest possible level.
This practical note is based on the following:
1. Deviating ambient temperature: The thermal releases are adapted to a given reference ambient temperature. For the K- and Z-type
characteristics, it is 20 °C, for B-, C- and D-type, it is 30 °C.
For all other ambient temperatures, the current values indicated vary by ca. 6 % per 10 K temperature de/increase.
For more precise calculations and very high/low ambient temperatures, the following tables apply:
Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type B, C and D
B, C and D Ambient temperature T (°C)
In (A) – 40 – 30 – 20 – 10 0 10 20 30 40 50 60 70
0.5 0.67 0.65 0.62 0.60 0.58 0.55 0.53 0.50 0.47 0.44 0.41 0.37
1.0 1.33 1.29 1.25 1.20 1.15 1.11 1.05 1.00 0.94 0.88 0.82 0.75
1,6 2.13 2.07 2.00 1.92 1,85 1.77 1.69 1.60 1.51 1.41 1.31 1.19
2,0 2.67 2.58 2.49 2.40 2.31 2.21 2.11 2.00 1.89 1.76 1.63 1.49
3,0 4.0 3.9 3.7 3.6 3.5 3.3 3.2 3.0 2.8 2.6 2.4 2.2
4,0 5.3 5.2 5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.5 3.3 3.0
6,0 8.0 7.7 7.5 7.2 6.9 6.6 6.3 6.0 5.7 5.3 4.9 4.5
8,0 10.7 10.3 10.0 9.6 9.2 8.8 8.4 8.0 7.5 7.1 6.5 6.0
10,0 13.3 12.9 12.5 12.0 11.5 11.1 10.5 10.0 9.4 8.8 8.2 7.5
13,0 17.3 16.8 16.2 15.6 15.0 14.4 13.7 13.0 12.3 11.5 10.6 9.7
16,0 21.3 20.7 20.0 19.2 18.5 17.7 16.9 16.0 15.1 14.1 13.1 11.9
20,0 26.7 25.8 24.9 24.0 23.1 22.1 21.1 20.0 18.9 17.6 16.3 14.9
25,0 33.3 32.3 31.2 30.0 28.9 27.6 26.4 25.0 23.6 22.0 20.4 18.6
32,0 42.7 41.3 39.9 38.5 37.0 35.4 33.7 32.0 30.2 28.2 26.1 23.9
40,0 53.3 51.6 49.9 48.1 46.2 44.2 42.2 40.0 37.7 35.3 32.7 29.8
50,0 66.7 64.5 62.4 60.1 57.7 55.3 52.7 50.0 47.1 44.1 40.8 37.3
63,0 84.0 81.3 78.6 75.7 72.7 69.6 66.4 63.0 59.4 55.6 51.4 47.0
Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type K and Z
K and Z Ambient temperature T (°C)
In (A) – 40 – 30 – 20 – 10 0 10 20 30 40 50 60 70
0.5 0.66 0.64 0.61 0.59 0.56 0.53 0.50 0.47 0.43 0.40 0.35 0.31
1.0 1.32 1.27 1.22 1.17 1.12 1.06 1.00 0.94 0.87 0.79 0.71 0.61
1.6 2.12 2.04 1.96 1.88 1.79 1.70 1.60 1.50 1.39 1.26 1.13 0.98
2.0 2.65 2.55 2.45 2.35 2.24 2.12 2.00 1.87 1.73 1.58 1.41 1.22
3.0 4.0 3.8 3.7 3.5 3.4 3.2 3.0 2.8 2.6 2.4 2.1 1.8
4.0 5.3 5.1 4.9 4.7 4.5 4.2 4.0 3.7 3.5 3.2 2.8 2.4
6.0 7.9 7.6 7.3 7.0 6.7 6.4 6.0 5.6 5.2 4.7 4.2 3.7
8.0 10.8 10.2 9.8 9.4 8.9 8.5 8.0 7.5 6.9 6.3 5.7 4.9
10.0 13.2 12.7 12.2 11.7 11.2 10.6 10.0 9.4 8.7 7.9 7.1 6.1
13.0 17.2 16.6 15.9 15.2 14.5 13.8 13.0 12.2 11.3 10.3 9.2 8.0
16.0 21.2 20.4 19.6 18.8 17.9 17.0 16.0 15.0 13.9 12.6 11.3 9.8
20.0 26.5 25.5 24.5 23.5 22.4 21.2 20.0 18.7 17.3 15.8 14.1 12.2
25.0 33.1 31.9 30.6 29.3 28.0 26.5 25.0 23.4 21.7 19.8 17.7 15.3
32.0 42.3 40.8 39.2 37.5 35.8 33.9 32.0 29.9 27.7 25.3 22.6 19.6
40.0 52.9 51.0 49.0 46.9 44.7 42.4 40.0 37.4 34.6 31.6 28.3 24.5
50.0 66.1 63.7 61.2 58.6 55.9 53.0 50.0 46.8 43.3 39.5 35.4 30.6
63.0 83.3 80.3 77.2 73.9 70.4 66.8 63.0 58.9 54.6 49.8 44.5 38.6
2. Interdependencies in
the case of even loads
A correction factor must be
taken into account in the
case butt-mounted devices
and an evenly applied, high
load:
2 and 3 circuit-breakers
with factor 0.9
4 and 5 circuit-breakers
with factor 0.8
6 and more circuit-breakers
with factor 0.75
The interdependency
becomes irrelevant if
FST … spacers or
packing blocks (9mm
width) are used.
The influence of ambient temperature and interdependencies in the case of even loads on the load
capability of MCBs
Practical Note: This practical deduction, that is applicable for all types of characteristics, can be recommended for standard
environments. Selection criteria for rated current of circuit-breakers according to EN 60898 and EN 60947-2.
Choose the circuit-breaker that is appropriate for the lower of the rated value of the device or the permissible current loading.
Now, the major factors having an influence on the circuit-breaker, must be taken into account:
1. ambient temperature with IB 0.9 x In at 40 °C ambient temperature
2. mutual influence with IB 0.75 x In in the case of more than one circuit-breaker being loaded evenly in parallel.
The ensuing rated current of the circuit breaker is thus: In = 1.5 x rated current
Example: operating currect 4 A, then the rated current of the circuit-breaker is: In = 1.5 x 4 A = 6 A
The above takes into account all relevant factors and the circuit is protected at the lowest possible level.
This practical note is based on the following:
1. Deviating ambient temperature: The thermal releases are adapted to a given reference ambient temperature. For the K- and Z-type
characteristics, it is 20 °C, for B-, C- and D-type, it is 30 °C.
For all other ambient temperatures, the current values indicated vary by ca. 6 % per 10 K temperature de/increase.
For more precise calculations and very high/low ambient temperatures, the following tables apply:
Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type B, C and D
B, C and D Ambient temperature T (°C)
In (A) – 40 – 30 – 20 – 10 0 10 20 30 40 50 60 70
0.5 0.67 0.65 0.62 0.60 0.58 0.55 0.53 0.50 0.47 0.44 0.41 0.37
1.0 1.33 1.29 1.25 1.20 1.15 1.11 1.05 1.00 0.94 0.88 0.82 0.75
1,6 2.13 2.07 2.00 1.92 1,85 1.77 1.69 1.60 1.51 1.41 1.31 1.19
2,0 2.67 2.58 2.49 2.40 2.31 2.21 2.11 2.00 1.89 1.76 1.63 1.49
3,0 4.0 3.9 3.7 3.6 3.5 3.3 3.2 3.0 2.8 2.6 2.4 2.2
4,0 5.3 5.2 5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.5 3.3 3.0
6,0 8.0 7.7 7.5 7.2 6.9 6.6 6.3 6.0 5.7 5.3 4.9 4.5
8,0 10.7 10.3 10.0 9.6 9.2 8.8 8.4 8.0 7.5 7.1 6.5 6.0
10,0 13.3 12.9 12.5 12.0 11.5 11.1 10.5 10.0 9.4 8.8 8.2 7.5
13,0 17.3 16.8 16.2 15.6 15.0 14.4 13.7 13.0 12.3 11.5 10.6 9.7
16,0 21.3 20.7 20.0 19.2 18.5 17.7 16.9 16.0 15.1 14.1 13.1 11.9
20,0 26.7 25.8 24.9 24.0 23.1 22.1 21.1 20.0 18.9 17.6 16.3 14.9
25,0 33.3 32.3 31.2 30.0 28.9 27.6 26.4 25.0 23.6 22.0 20.4 18.6
32,0 42.7 41.3 39.9 38.5 37.0 35.4 33.7 32.0 30.2 28.2 26.1 23.9
40,0 53.3 51.6 49.9 48.1 46.2 44.2 42.2 40.0 37.7 35.3 32.7 29.8
50,0 66.7 64.5 62.4 60.1 57.7 55.3 52.7 50.0 47.1 44.1 40.8 37.3
63,0 84.0 81.3 78.6 75.7 72.7 69.6 66.4 63.0 59.4 55.6 51.4 47.0
Max. operating current depending on the ambient temperature circuit-breaker in load circuit of characteristics type K and Z
K and Z Ambient temperature T (°C)
In (A) – 40 – 30 – 20 – 10 0 10 20 30 40 50 60 70
0.5 0.66 0.64 0.61 0.59 0.56 0.53 0.50 0.47 0.43 0.40 0.35 0.31
1.0 1.32 1.27 1.22 1.17 1.12 1.06 1.00 0.94 0.87 0.79 0.71 0.61
1.6 2.12 2.04 1.96 1.88 1.79 1.70 1.60 1.50 1.39 1.26 1.13 0.98
2.0 2.65 2.55 2.45 2.35 2.24 2.12 2.00 1.87 1.73 1.58 1.41 1.22
3.0 4.0 3.8 3.7 3.5 3.4 3.2 3.0 2.8 2.6 2.4 2.1 1.8
4.0 5.3 5.1 4.9 4.7 4.5 4.2 4.0 3.7 3.5 3.2 2.8 2.4
6.0 7.9 7.6 7.3 7.0 6.7 6.4 6.0 5.6 5.2 4.7 4.2 3.7
8.0 10.8 10.2 9.8 9.4 8.9 8.5 8.0 7.5 6.9 6.3 5.7 4.9
10.0 13.2 12.7 12.2 11.7 11.2 10.6 10.0 9.4 8.7 7.9 7.1 6.1
13.0 17.2 16.6 15.9 15.2 14.5 13.8 13.0 12.2 11.3 10.3 9.2 8.0
16.0 21.2 20.4 19.6 18.8 17.9 17.0 16.0 15.0 13.9 12.6 11.3 9.8
20.0 26.5 25.5 24.5 23.5 22.4 21.2 20.0 18.7 17.3 15.8 14.1 12.2
25.0 33.1 31.9 30.6 29.3 28.0 26.5 25.0 23.4 21.7 19.8 17.7 15.3
32.0 42.3 40.8 39.2 37.5 35.8 33.9 32.0 29.9 27.7 25.3 22.6 19.6
40.0 52.9 51.0 49.0 46.9 44.7 42.4 40.0 37.4 34.6 31.6 28.3 24.5
50.0 66.1 63.7 61.2 58.6 55.9 53.0 50.0 46.8 43.3 39.5 35.4 30.6
63.0 83.3 80.3 77.2 73.9 70.4 66.8 63.0 58.9 54.6 49.8 44.5 38.6