DC String Combiner Box 2 Strings 800V 25A Isolators IP65
IP65 DC field box for 2 independent PV strings up to 800 V, 25 A per string. Load-break isolator and gPV fuse on each string – current rating sized for high-Isc TOPCon and HJT modules.
The QDC-SEZ DC field box protects and isolates two independent PV strings up to 800 V DC, rated 25 A per string. The higher current rating is designed for the latest module generation – TOPCon and heterojunction (HJT) – whose short-circuit current (Isc) often exceeds 14-18 A. Each string has its own load-break isolator.
The isolator (SEZ): why a fuse is not enough
Direct current has no zero-crossing: once an arc is struck, it does not extinguish on its own. A fuse protects the conductor against overcurrent but must never be used as a switching device under load. The load-break isolator is built to open the DC circuit safely under load – for maintenance, fault-finding or emergency disconnection.
| Strings | 2 independent |
| Max voltage | 800 V DC |
| Current per string | 25 A |
| Enclosure | IP65, 18 DIN modules |
| Protection | Isolator + gPV fuse per string |
Note on the fuse: the 25 A rating refers to the nominal current per string; the box is fitted with a gPV 32 A / 1000 V fuse whose tripping curve is matched to the short-circuit current (Isc) of the modules.
When to choose this box
The 25 A rating is the right choice when module Isc is high, as with high-current-density TOPCon and HJT cells. Check that each string's Isc (multiplied by the safety factor required by the standard) stays within 25 A, and that the cold Voc does not exceed 800 V.
FAQ
Why 25 A and not 16 A?
TOPCon and HJT modules have a higher short-circuit current than traditional modules. The 25 A rating provides the margin these high-Isc technologies require.
Can I isolate one string without interrupting the other?
Yes. Each string has its own isolator, so you can isolate one for maintenance while the other keeps producing.
Does installation require a qualified technician?
Yes. Installation and connection to the PV system must be carried out by a qualified installer, in compliance with the applicable standards (including CEI 0-21/0-16 and EN IEC 62548).