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All rights reserved.
18
String Optimizer V600-32 Platform
Installation Manual: 57070021-1 A
Fuses
CAUTION
Over-current protection devices and conductors shall be sized in accordance with
the National Electrical Code (ANSI/NFPA 70); Canadian Electrical Code, Part I;
or the applicable standards, codes, and regulations for your region.
Understanding Maximum Output Current and Fuse Sizing
The recommended PV system design ensures that the DC bus voltage, which is set by the
inverter, is always greater than the optimizer input voltages. For these systems, the maximum
output current will be the
Maximum output current
listed on the optimizer’s
datasheet.
This design allows the output current limit of the Ampt String Optimizer to eliminate the need
for the 1.25 multiplication factor for over-sun conditions when calculating ampacity. The 1.25
multiplier for continuous use is still required.
Optimizer Max
Output Current (A)
Minimum Standard
Fuse Size (A)
20
25
24
30
25
32
28
35
30
40
32
40
For other system designs where the DC bus voltage can be less than the voltage on either
optimizer input, the potential maximum output current will either be the
Maximum output
current
listed on the optimizer’s datasheet or
the maximum input current
–
whichever is
greater. If the maximum output current is the one listed on the optimizer datasheet, use the
table above. Otherwise, use your standard fuse sizing method including margins for both over-
sun and continuous use.
Input Fuses
For single PV strings on an optimizer input, an input fuse may be required to protect the
modules in the event of an array fault when the maximum series fuse rating for the PV modules
is less than the output fuse rating. For parallel PV strings on an optimizer input, always use
fuses to protect the PV modules.
