SMA AUTOMATIC SWITCH BOX M-20 - Manual (Page 33)

SMA Solar Technology AG 5 Electrical Connection
Installation Guide AS-BOX-M_L-IA-IEN110320 33
5.5 Connecting Loads
Overcurrent protective device and switch-disconnector:
During stand-alone grid operation, the Sunny Backup and the PV plant supply the loads. This disables
the fuse on the grid side. During stand-alone grid operation, the fuse-switch-disconnector "AS-F5"
protects the loads' cables against overload.
Requirements for the residual current device in the TT system:
☐ The nominal tripping current is 100 mA maximum.
☐ Secure tripping with several residual current devices is provided if
g x ΣI
ΔN
≤ 100 mA.
g = coincidence factor of the residual current devices
ΣI
ΔN
= total of nominal tripping currents of the residual current devices
Coincidence factor
g = 1 corresponds to 1 residual current device in the system.
g = 0.5 corresponds to 2 ... 4 residual current devices in the system.
g = 0.35 corresponds to 5 ... 10 residual current devices in the system.
g = 0.25 corresponds to > 10 residual current devices in the system.
Risk of lethal electric shock in the TT system without personal protection.
• Install residual current devices between the Backup system and the loads' electric circuit.