PV String Combiner Box 5 Strings 1000V IP65 SecSun QCM5105L
SecSun QCM5105L photovoltaic string combiner box for DC-side protection of PV systems with up to 5 strings at 1000 VDC. It combines string fuses, independent disconnection and surge protective devices (SPD) in a single enclosure.
Wall-mounted PVC enclosure rated IP65: a compact LIGHT version, also suitable for outdoor installation.
The SecSun QCM5105L combiner box is the compact solution to protect the DC side of a photovoltaic system with up to 5 strings at 1000 VDC. It gathers in a single box all the protections required between the modules and the inverter: string fuses, independent disconnection and surge protective devices. It belongs to the LIGHT line, designed for small and medium-sized residential and commercial systems.
Why do you need a DC combiner box?
Between the solar panels and the inverter the DC voltage can reach 800-1000 V: a fault or an overvoltage on this section must be isolated and diverted before it reaches the inverter or the system. PV design standards (IEC 62548) require DC-side string protection with dedicated fuses, a disconnection device and surge protective devices. The combiner box performs all three functions in a single enclosure.
QCM5105L technical specifications
| Type | DC combiner box (string box), LIGHT line |
| Number of strings | 5 independent strings |
| Maximum DC voltage | 1000 VDC |
| Short-circuit protection | 5 two-pole (2P) fuse holders with 16 A - 1000 VDC fuses |
| Disconnection | 5 disconnector switches 16 A - 1000 VDC (one per string) |
| Surge protection | 5 surge protective devices (SPD) 1000 VDC |
| Enclosure | Wall-mounted PVC (thermoplastic) box |
| Protection rating | IP65 (suitable for outdoor installation) |
| Weight | approx. 3 kg |
Integrated protection, one set per string
The distinctive feature of the QCM5105L is that each string has its own set of protections: two-pole fuse holder, disconnector and surge arrester. This lets you disconnect and secure a single string — for maintenance, testing or module replacement — without shutting down the entire PV array. The 16 A fuses protect each string from reverse currents; the SPDs divert indirect atmospheric overvoltages to earth, safeguarding the inverter and the modules.
Where it is installed
The box should be placed between the modules and the inverter, as close as possible to the PV generator. Thanks to its IP65 rating and PVC enclosure it can be wall-mounted outdoors too. It is suitable for systems with up to 5 strings: medium-to-large residential systems and small commercial plants.
What is included
- Assembled and wired box with 5 two-pole fuse holders and 16 A - 1000 VDC fuses
- 5 disconnector switches 16 A - 1000 VDC
- 5 surge protective devices (SPD) 1000 VDC
- Wall-mounted PVC IP65 enclosure
Frequently asked questions
How many strings can I connect to the QCM5105L?
Up to 5 independent PV strings, each with its own fuse, disconnector and surge arrester. Every input works up to 1000 VDC.
Can I disconnect a single string without shutting down the system?
Yes. Each string has its own disconnector switch, so you can isolate and secure one string for maintenance or testing while the other four keep producing.
What are the surge protective devices (SPD) for?
SPDs protect the system from transient overvoltages, typically of indirect atmospheric origin such as nearby lightning. They divert the voltage peak to earth before it can damage the inverter and the modules.
What is the difference between the LIGHT and the PRO version?
The LIGHT line offers the essential string protections (fuses, disconnection and SPD) in a compact and cost-effective enclosure, suitable for small and medium systems. The PRO versions add components and options designed for larger plants or for those requiring monitoring.
Is the box suitable for outdoor installation?
Yes. The enclosure is made of PVC with an IP65 protection rating, so it withstands dust and water jets and can be wall-mounted outdoors.
