SMA SB 1100LV User Manual
Page 52
Rating for a line circuit breaker
SMA
Technologie AG
Page 52
SB1100LV-11:SE2006
Installation Guide
When selecting line circuit breakers, a number of load factors need to be taken into
account. These can be found in the respective data sheets.
For example, one manufacturer's circuit breaker may be designed for an ambient
temperature of 50 °C.
Load factors according to data sheet specifications:
•
Reduction through permanent load >1h = 0.9
a
•
Reduction when 9 circuit breakers are arranged side-by-side without gaps
= 0.77
b
•
Increase in nominal current as a result of ambient temperatures of 40 °C in the
circuit breaker panel = 1.07
c
Result:
The nominal load current for the line circuit breaker is calculated as:
Ibn = 10 A x 0.9 x 0.77 x 1.07 = 7.4 A
Example for the thermal selection of a 10 A line circuit breaker with B sensitivity
with no gap between the circuit breakers:
a. Permanent loads of longer than 1 hour are possible in photovoltaics.
b. When only one circuit breaker is used, this factor = 1
c. Because the circuit breakers are rated for 50 °C