The following points regarding cabling must be considered:
- The main contacts of contactors K1 and K2 must be installed between the Fronius
Smart Meter and the residual current circuit breaker of the inverter and the residual
current circuit breaker of the backup power circuits.
- The supply voltage for contactors K1 and K2 is provided by the public grid and must
be connected to phase 1 (L1) after the Fronius Smart Meter and fused accordingly.
- To ensure residual current circuit breakers function in backup power mode, the con-
nection between the neutral conductor and the ground conductor must be estab-
lished as close as possible to the inverter, but in any case before the first residual
current circuit breaker. An NC contact is used for this purpose for each of the main
contacts of contactors K4 and K5. This ensures that the ground connection is estab-
lished as soon as the public grid connection is no longer available.
- As with contactor K1, the supply voltage for contactors K4 and K5 is provided via
phase 1 (L1) of the public grid.
- An NC contact for the relay K3 interrupts the supply voltage to contactors K1, K2, K4
and K5. This prevents the ground connection from being immediately disconnected
again when power returns to the public grid and the backup power network of the
inverter from being switched to the public grid.
- The NO contact of relay K3 gives feedback to the inverter on whether the locking
was successfully performed by relay K3.
- Additional inverters or other AC sources can be installed in the backup power circuit
after the main contacts of K1 and K2. The sources are not synchronised to the net-
work of the inverter because this backup power network has a frequency of 53 Hz.
- A Fronius Smart Meter with current transformer is required (e.g. Fronius Smart
Meter 50kA-3 or Fronius Smart Meter TS 5kA-3).
All-pin separation
cabling variant,
e.g. Italy
Circuit Diagram
The Circuit Diagram for the 2-pin double separation with ext. grid and system protection -
e.g. Italy, can be found in the appendix to this document on page 152.
Backup power circuit and non-backup power circuits
IMPORTANT!
Fronius Smart Meter US-240 must be used for these circuit variants.
The backup power circuits and non-backup power circuits must be fused separately
according to the required safety measures (residual current circuit breaker, automatic cir-
cuit breaker, etc.).
In backup power mode, only the backup power circuits are disconnected from the grid by
contactors K1 and K2; an earth connection is only established for these circuits. The rest
of the home network is not supplied with power in this case.
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