Installation Manual

PRELIMINARY

String Optimizer V1500-30 Series

Installation Manual: 57070016-1

v20201023

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 Fuse Size (A)

37.5 (40 A standard)

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.