PV DC combiner box 1000V T1 T2 MC4 2-string Doktorvolt 2421 DV-2421-FOT

Dual-string DC protection for photovoltaic installations

The DV-2421-FOT photovoltaic distribution board is a complete solution for receiving and protecting two strings in PV installations operating at voltages up to 1000V DC. The device integrates all key elements needed to safely connect photovoltaic modules to the inverter within a single enclosure - eliminating the need to select and purchase separate components.

IP65 Enclosure - durability in all conditions

The enclosure is made of technopolymer - a material resistant to UV radiation, moisture, and typical chemicals encountered on roofs and facades. Dimensions of 215 × 210 × 100 mm (with PG cable glands: 215 × 240 × 100 mm) allow for free arrangement of wiring inside without the cramped feeling typical of cheaper solutions. The door is made of polycarbonate - a material harder than the body itself, which reduces the risk of cracking upon impact or intensive use.

Tightness at the IP65 level means full dust-tightness and protection against water jets directed from any angle. The seal is made of EPDM rubber, which maintains flexibility across a wide temperature range - it does not harden in frost nor soften excessively in summer. Stainless steel screws do not require periodic tightening or replacement throughout the entire service life of the enclosure.

The grey RAL 7035 color scheme is a standard choice for electrical fittings - neutral, easy to keep clean, and highly visible against dark roof surfaces.

T1+T2 Surge Protection - a double barrier for strings

The safety of the DC circuits is ensured by two Phoenix Contact VAL-MS-T1/T2 surge arresters. This is a two-stage solution:

• Class T1 (Class B) - an impulse current of 15 kA, protecting against direct lightning strikes. It absorbs the energy of a lightning strike even if it hits close to the installation.
• Class T2 (Class C) - a maximum current of 40 kA, eliminating secondary surges caused by distant atmospheric discharges or the switching of large loads.

The voltage protection level is Up < 3.5 kV, which effectively limits the residual voltage at the terminals of the protected device below the damage threshold of typical PV modules. The maximum operating voltage Uc is 1050V DC, so the margin to the nominal voltage is sufficient even in cold weather, when modules generate higher voltage than in standard STC conditions.

The manufacturer declares certificates: CE, product standard IEC 61643-11:2011, and the production process itself is carried out in a quality management system certified by TÜV SÜD (ISO 9001:2015).

Wiring and complete MC4 connector set

Inside the distribution board, you will find ready-to-use connections:

• BiT 1000 solar cables (6 mm²) - black and red, single-core, insulated for 0.6/1 kV. Cross-section sufficient for strings with power in the range of several dozen kilowatts.
• H07V-K grounding conductor (16 mm²) in yellow-green - dedicated to grounding connections.
• The PG-11 cable gland enables a tight entry for the main cable going to the inverter.

An additional set of up to 8 MC4 connectors (4x male + 4x female) is included with the distribution board. This is practically significant - each string requires two pairs of connectors (input + output), so eight pieces cover the full set needed for two strings without the need to purchase additional parts.

MC4 connectors operate at a working voltage of 1000 V AC/DC, withstand impulses of 8 kV, and have an IP67 protection rating. European standards IEC 62548 and IEC 60364-7-712:2017 explicitly prohibit mixing connectors from different manufacturers in a single DC circuit - geometric mismatch leads to an increase in contact resistance, which generates heat that can result in fire. The fa