I'm installing a system at my house, new to solar, reading about reverse currents and noting what my module manufacturer says about this in the installation manual. QCells says I need string fuses if I have more than 2 strings in parallel. I have a Midnight Solar combiner box with their 20A breakers. Is this insufficient for preventing issues with reverse currents? My plan is 3 strings in parallel (a total of 6 strings), with 37A/120V per string.
I called QCells but haven't heard back. Here's what they say in the install manual:
I called QCells but haven't heard back. Here's what they say in the install manual:
Parallel Connection
Modules may be damaged by the occurrence of reverse currents
(caused by module defects, ground leaks, or defective insulation).
Ensure that the maximum reverse current load capacity indicated
in the data sheet is met.
In order to limit reverse currents that may occur, we recommend
using the following safety options:
1) Layout with a limited number of parallel connected strings :
Without undertaking further current blocking measures, a maximum
of two module strings may be operated in parallel on an inverter or
MPP tracker.
2) Layout with string fuses :
place fuses for each string of modules at the plus and minus ends.
Observe the maximum permitted number of strings as indicated
in the specifications provided by the respective string fuse manufacturer
and the technical guidelines.
Modules may be damaged by the occurrence of reverse currents
(caused by module defects, ground leaks, or defective insulation).
Ensure that the maximum reverse current load capacity indicated
in the data sheet is met.
In order to limit reverse currents that may occur, we recommend
using the following safety options:
1) Layout with a limited number of parallel connected strings :
Without undertaking further current blocking measures, a maximum
of two module strings may be operated in parallel on an inverter or
MPP tracker.
2) Layout with string fuses :
place fuses for each string of modules at the plus and minus ends.
Observe the maximum permitted number of strings as indicated
in the specifications provided by the respective string fuse manufacturer
and the technical guidelines.
Comment