Metal Surge Arrestor Unit (WME440SP)

The WME440SP Metal Surge Arrestor Unit provides a simple and compliant way to add surge protection to an existing installation. Housed in a compact IP40-rated metal enclosure, it is supplied with a 100A main switch and a twin-pole 40kA Type 2 Surge Protection Device (SPD).

Installed between the meter and the consumer unit, this unit ensures compliance with the 18th Edition wiring regulations (Amendment 2), which require surge protection on most new circuits. Suitable for both domestic and light commercial installs. For outdoor use, see our IP65-rated enclosures.

• 100A main switch for secure isolation
• 40kA Type 2 SPD for overvoltage and lightning surge protection
• Compact design: only 4 modules wide
• IP40 steel enclosure with earthed lid
• Meets BS7671:2018 (A2) and BS EN 61439 requirements

Often paired with metal meter isolators or PME fault detection units to build fully regulation-compliant EV and renewable setups.

• Part code: WME440SP
• Incomer: 100A main switch
• SPD: Type 2, twin-pole, 40kA
• Enclosure: Metal, IP40 rated
• Modules: 4
• Dimensions: 110(W) × 175(H) × 91(D) mm
• Standards: BS EN 61439, BS7671:2018 (Amendment 2)

Designed for straightforward integration into existing installations. Must be installed by a qualified electrician.

• Fit between meter tails and the main consumer unit
• Ensure SPD earth conductor is kept as short as possible
• Check connections and test SPD before energising
• Maintain IP40 integrity when routing cables

Where should this surge arrestor unit be installed?

It is designed to be installed between the meter and the main consumer unit to provide system-wide surge protection. For direct integration into boards, see our standalone SPDs.

What type of SPD is included?

A twin-pole, 40kA Type 2 surge protection device, suitable for domestic and small commercial applications. For three-phase installs, see our 3 Phase SPD range.

Does this unit comply with the 18th Edition regs?

Yes – it meets the surge protection requirements set out in BS7671:2018 (Amendment 2). For EV and heat pump compliance, consider pairing with a PME Fault Detection Unit.

What size is the enclosure?

The unit is compact at just 110 × 175 × 91 mm, making it easy to fit in tight meter cupboard spaces. For larger setups with spare ways, see our Heat Pump Consumer Units which include surge protection as standard.