PV DC 1000V T2 distribution board Doktorvolt 9467 DV-9467-FOT-257-DC

Complete solution for single-string photovoltaic installations

The Doktorvolt DC photovoltaic distribution board is a prefabricated device for connecting strings to the installation - one string input, output to the inverter. Designed for operation in DC circuits up to 1000V, it is equipped with a T2 class surge protection device and a complete set of MC4 connectors included.

The enclosure is made of technopolymer (manufacturer Marlanvil IP65) with dimensions of 142 × 210 × 100 mm - it accommodates a row of modular devices four modules wide. The gray RAL 7035 color matches standard building joinery. The polycarbonate door provides visibility of the apparatus through a transparent cover - the installer can inspect the state of the connections without the need to open the distribution board. The EPDM rubber gasket and IP65 protection rating guarantee tightness even when mounted on the exterior of a building, where the enclosure is exposed to rain and dust.

Surface mounting allows for quick attachment to a wall or support structure using stainless steel screws (included). The dimensions with installed PG11 glands and MC4 connectors are 142 × 240 × 100 mm - the difference results from the protruding connectors on both sides of the enclosure.

Electrical equipment and wiring

The surge protection device is a 3-pole T2 class varistor (designation C) dedicated to DC circuits. The rated voltage is 1000V DC, and the maximum operating voltage Uc reaches 1060V DC. The test current In is 20 kA, with a maximum current Imax reaching 40 kA. The Up protection level remains below 4.0 kV.

Such selected parameters allow the SPD to effectively absorb surge energy generated by atmospheric discharges or grid switching - during a surge, it "escapes" into a conduction state, protecting the PV modules and the inverter.

Internal wiring consists of 6 mm² solar cables (black and red) and a yellow-green H07V-K 16 mm² as a PE protective conductor. The wire cross-section was selected based on string currents typical for residential installations - at lengths of up to several dozen meters, the voltage drop remains within the norm.

Factory-mounted MC4 solar connectors (one female and one male set on each pole) allow for immediate connection of the string cables. An additional set of two pairs of MC4 included in the kit enables making connections on the module or inverter side without the need to purchase additional connectors.

The connectors operate in a temperature range from -40°C to +105°C, have a contact resistance below 0.5 mΩ, an impulse voltage of 8 kV, and protection class II (reinforced insulation).

Standards, certificates, and connection safety

The manufacturer declares quality management system certification by TÜV SÜD and compliance with the following standards:

• IEC 61439 - modular distribution boards,
• CE,
• RoHS,
• Eu 2002/95/EC,
• CEI 23-48,
• ISO 9001:2015.

The enclosure has an IK07 mechanical impact resistance rating.

The IEC EN standard distinguishes two approaches to designing PV systems - one allows the use of isolating switches as the sole disconnectable means between the modules and the inverter. In practice, the string distribution board serves as the DC circuit separation point - it enables the isolation of the string from the inverter during servicing or failure.

The manufacturer draws attention to the risk resulting from using solar connectors from different manufacturers. MC4 connectors of different brands may have slightly different dimensions for contacts and seals - imprecise fitting causes an increase in contact resistance at the connection. Contact resistance generates Joule heat proportional to the square of the string current; in PV installations operating under load for years, this point can reach a critical temper