DC String Combiner Box 1 String 800V 25A with Isolator IP65
Single-string DC field combiner box (1 IN / 1 OUT) up to 800 V, 25 A, with isolator, to be installed between the modules and the inverter. It integrates a 32 A fuse holder, an 800 V DC isolator and an 800 V SPD surge protector, with input and output terminal blocks.
IP65 box with 8 DIN modules, components labelled on plastic-coated rails.
The QDC-01/01 SEZ DC field combiner box in the 800 V 25 A version protects and isolates a single high-current photovoltaic string. It is installed between the module array and the inverter and brings together the three DC-side functions: isolating the string for maintenance, protecting it with a fuse holder, and discharging overvoltages to earth before they reach the MPPT.
The isolator (SEZ): why a fuse alone is not enough
The SEZ designation indicates an on-board DC isolator. The DC side has no zero crossing: opening a string under load with an unsuitable device generates an arc that does not extinguish by itself. The built-in isolator is rated for 800 V direct current and can be operated under load, making it possible to isolate the string safely without shutting down the whole system.
QDC-01/01-800V-25A SEZ technical specifications
| Configuration | 1 string IN / 1 OUT |
| Rated voltage | 800 V DC |
| Current | 25 A |
| String protection | 1 fuse holder with 32 A 1000 V DC fuse |
| Isolation | 1 DC isolator 800 V |
| Overvoltages | 1 SPD surge arrester 800 V |
| Connections | Input and output terminal blocks |
| Enclosure | IP65 box with 8 DIN modules |
| Weight | 4 kg |
Why the 25 A version: high-current modules
The 800 V / 25 A combination is the choice for strings with high-current modules: modern TOPCon and HJT modules reach 14-18 A of Isc, and the panel's 25 A provide the margin that a 16 A size does not guarantee. It is the most overlooked design check: an isolator undersized on current runs at its limit and ages sooner. The 800 V ceiling must still be checked against the string's cold Voc and the inverter MPPT.
Frequently asked questions
What is the difference from the version without an isolator?
The SEZ version integrates the DC isolator that lets you isolate the string under load for maintenance. Without an isolator, isolation must be provided elsewhere, typically at the inverter input.
When do you need 25 A instead of 16 A?
When the modules' short-circuit current (Isc) approaches or exceeds the values covered by a 16 A size. Recent TOPCon and HJT modules have high Isc: the 25 A version keeps the correct margin on the isolator and the terminal blocks.
Is it suitable for outdoor installation?
The IP65 rating allows it. A position not exposed to the sun all day long is preferable: the internal temperature reduces the service life of the surge arresters.