String Fuses; Criteria For The Proper Selection Of String Fuses - Fronius Symo Serie Instructions De Service

String fuses

Only applies to device type Fronius Symo 15.0-3 208 and device types Fronius Symo
15.0-3 480 / 20.0-3 480 / 22.7-3 480 / 24.0-3 480 with the "Ecofuse" option:
The use of string fuses in the Fronius Symo provides additional fuse protection for solar
modules.
The maximum short circuit current I
specification of the maximum string fuse value in the module data sheet of the respective
solar module are decisive factors in the protection of the solar module.
The maximum short circuit current I
The string fuse release current can be set to greater than 15 A if required. However, a re-
lease current of 20 A must not be exceeded.
If the inverter is being operated with an external string collection box, the DC connector kit
25 (item numbers 42,0201,4479 for DC+ and 42,0201,4480 for DC-) must be used. In this
case the solar modules are externally protected in the string collection box and the metal
bolts should be used in the inverter.
National regulations regarding fuse protection must be observed. The electrician perform-
ing the installation is responsible for choosing the right string fuses.
The inverter is delivered with metal bolts as standard.
DC+ 1.3
DC+ 1.2
Criteria for the The following criteria must be met for each solar module string when using fuse protection:
Proper Selection
of String Fuses -
-
-
-
I
N
I
SC
V
N
NOTE! To prevent a risk of fire, faulty fuses must only be replaced by new equiv-
alent fuses.
Option DC SPD
DC+ 2.1
Do not remove cover! Do not remove cover!
DC+ 1.1
I > 1.8 x I
N SC
I < 2.4 x I
N SC
V >/= maximum open circuit voltage of pv generator
N
Fuse dimensions: Diameter 10 x 38 mm
Nominal current of the fuse
Short circuit current for standard test conditions (STC) according to solar module
data sheet
Nominal voltage of the fuse
, the maximum module backfeed current I
SC
per terminal is 15 A.
SC
DC+ 2.3 DC- 1.2
DC+ 2.2 DC- 1.1
Each Terminal: I Each Terminal: I = 15 A = 15 A
max max
and the
R
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