WCED Solar PV Combiner Boxes — 1000V DC
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WCED Solar PV Combiner Boxes — 1000V DC
A solar combiner box does three things that matter: it brings one or two PV string cables to a single organised connection point, it provides a safe DC disconnect so the inverter can be isolated without touching the array, and it absorbs surge energy from lightning-induced overvoltages in the string cables before they can reach the inverter's sensitive DC input electronics.
The WCED range covers the most common domestic and light commercial configurations — 1-string and 2-string, in metal and polycarbonate enclosures — all rated to 1000V DC and supplied ready to install.
Choose your model
All prices ex. VAT. Same-day dispatch on stock lines. Competitor equivalent (Electrical4less WPPV-1S1): £71.21 ex. VAT.
What's inside every combiner box
Metal vs plastic — which should I choose?
| Feature | Metal (WMPV) | Plastic polycarbonate (WPPV) |
|---|---|---|
| — | IP65 steel enclosure | IP65 polycarbonate enclosure |
| — | Higher mechanical protection — IK10 | Lightweight, corrosion-resistant |
| — | Better for commercial or exposed locations | Ideal for domestic external walls and roof spaces |
| — | Non-conductive internal DIN rail | Fully non-conductive body — no bonding required |
| — | Slightly heavier — more robust feel | UV stabilised — suitable for direct sun exposure |
For most domestic rooftop or outbuilding installations, either enclosure type is suitable. The plastic WPPV is the most popular choice for domestic use — lighter, inherently non-conductive, and UV stabilised. The metal WMPV is preferred for more exposed commercial locations or where a higher level of mechanical protection is specified.
1-string vs 2-string — which do I need?
The string count refers to how many independent PV string cables connect into the combiner box. On a typical domestic installation with a single MPPT inverter and one string of panels, a 1-string (1S1) unit is correct. For systems with two strings — either two strings into a single MPPT input, or two independent MPPT inputs on a dual-tracker inverter — a 2-string (2S2) unit brings both string cables to one protected, organised connection point.
| Configuration | Model required | Example |
|---|---|---|
| — | 1-string: WMPV-1S1 or WPPV-1S1 | Single string, 1 MPPT input — most domestic systems up to ~4kW |
| — | 2-string: WMPV-2S2 or WPPV-2S2 | Two strings — dual MPPT inverter, east/west split array, or larger systems |
Where it fits in a solar installation
The combiner box installs between the PV array output and the inverter's DC input terminals. Typically it is mounted on the external wall near where the string cables enter the building, in the roof space, or adjacent to the inverter. All four WCED models are IP65 rated for outdoor installation — they can be mounted externally on the building fabric or in a sheltered outdoor location.
On the AC side of the inverter, a Type 2 AC SPD at the consumer unit provides protection for the inverter's grid connection. The combiner box DC SPD and the AC consumer unit SPD together provide complete surge protection for the full PV installation. See: Surge protection for solar and heat pumps
Full specifications
| Specification | WMPV-1S1 / WPPV-1S1 | WMPV-2S2 / WPPV-2S2 |
|---|---|---|
| Max DC voltage | 1000V DC | 1000V DC |
| String inputs / outputs | 1 in / 1 out | 2 in / 2 out |
| Max current per string | 32A | 32A |
| DC isolator rating | 45A | 45A |
| String fuse rating | 15A per string | 15A per string |
| SPD type | Type 2 DC, 20/40kA | Type 2 DC, 20/40kA |
| SPD voltage rating | 1000V DC | 1000V DC |
| Enclosure rating | IP65 IK10 | IP65 IK10 |
| Enclosure material | Metal (WMPV) / Polycarbonate (WPPV) | Metal (WMPV) / Polycarbonate (WPPV) |
| Cable entry | Cable glands — maintain IP65 | Cable glands — maintain IP65 |
| Mounting | Wall-mounted, surface fix | Wall-mounted, surface fix |
| Standard | EN 61439-2 (metal) / EN 61439-3 (plastic) | EN 61439-2 (metal) / EN 61439-3 (plastic) |
| Suitable for | Domestic and light commercial PV | Domestic and light commercial PV |
All four models in stock. Same-day dispatch on orders before 3pm. Also available: standalone DC SPDs (WSPV1000 / WSPV600) for custom combiner arrangements.
View full WCED range →Frequently Asked Questions
Do I need a combiner box or can I connect directly to the inverter?
For a single-string system, connecting directly to the inverter is possible — but you lose the DC disconnect point, the string fusing, and the surge protection that a combiner box provides. Most MCS-accredited installers specify a combiner box as standard practice for any PV installation. The DC disconnect is particularly valuable for safe servicing without needing to cover panels or disconnect at module connectors.
Is a 1000V DC combiner box suitable for all domestic solar inverters?
Yes — most domestic string inverters operate at DC string voltages between 200V and 600V under normal conditions, well within the 1000V DC rating of these units. The 1000V rating provides a safe margin and future-proofs the installation for higher-voltage string configurations.
What fuse rating should I use per string?
The WCED combiner boxes are supplied with 15A gPV fuses per string as standard, suitable for most domestic PV strings with panels rated up to around 10–11A short circuit current (Isc). If your panels have a higher Isc — check the panel datasheet — the fuse rating should be selected to exceed the panel Isc but not exceed the string cable rating. Always verify against the panel manufacturer's datasheet.
Can this combiner box be installed outdoors?
Yes — all four models are IP65 rated and suitable for outdoor installation. Cable glands must be correctly fitted and sized for the cable diameter to maintain the IP65 rating. The polycarbonate WPPV models use UV-stabilised polycarbonate suitable for direct sunlight exposure. The metal WMPV models should have any cut or exposed edges treated to prevent corrosion in coastal or high-humidity environments.
Does a DC combiner box SPD replace the need for AC surge protection?
No — they protect different parts of the system. The DC combiner box SPD protects against surges arriving via the PV string cables from the array. An AC Type 2 SPD at the consumer unit protects the inverter's AC output connection and the rest of the property's circuits. Both are needed for complete surge protection on a solar installation. See: Surge protection for solar and heat pumps
What is the difference between the metal and plastic combiner box at the same string count?
Both the metal (WMPV) and plastic (WPPV) variants at the same string count contain identical internal components — the same DC isolator, fuses, and SPD. The difference is purely the enclosure: steel for the metal versions, UV-stabilised polycarbonate for the plastic. Both are IP65 IK10. Choose metal where higher mechanical robustness or a more commercial aesthetic is required; choose plastic for typical domestic wall-mount applications where weight and non-conductivity are advantages.
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