Combination Surge Arrestor 40kA with NPE, 1+1 & 3+1 Module | Onesto SPD

The Onesto BY7-40 Combination Surge Protection Device is a compact, DIN rail mounted surge arrestor combining line and neutral-to-earth (NPE) protection in a single narrow module. Rated at 40kA, it is available in a 2-module 1+1 (single pole + neutral) configuration for single-phase boards, or a 4-module 3+1 (three pole + neutral) configuration for three-phase boards, at 275V or 385V. It is a practical, space-saving choice for boards needing a higher discharge rating than the 20kA combination unit, while still combining line and neutral protection in one compact housing.

• Application: Suitable for TN/TT distribution boards requiring combined line and neutral-to-earth protection at a higher discharge rating
• Key specification: 40kA maximum discharge current (Imax), Class II / Type 2 SPD
• Configuration: 1+1 module (single-phase + neutral) or 3+1 module (three-phase + neutral)
• Voltage: 275V or 385V operating voltage options
• Space-saving: Combines line and NPE protection in one compact DIN rail unit
• Status indicator: Green/red indication window shows functional or failed status

Key Features

• Combines line surge protection and neutral-to-earth (NPE) protection in a single compact DIN rail module, saving board space compared to separate devices
• 40kA maximum discharge current (Imax), 20kA nominal discharge current (In)
• Voltage protection level (Up) of approximately 2.0kV
• Visual green (functional) / red (failed) indication window
• PA66 UL94-V0 flame-retardant housing, IP20 degree of protection
• Suitable for TN and TT earthing systems

Typical Applications

• Domestic and commercial distribution boards with limited DIN rail space needing a higher discharge rating
• Single-phase boards requiring 1+1 (line + neutral) protection
• Three-phase boards requiring 3+1 (three-phase + neutral) protection
• Farm, rural and commercial properties needing combined line/neutral surge protection with greater surge exposure
• Retrofitting combined SPD protection into existing boards

Technical Specifications

What's Included

• 1 x Onesto BY7-40 Combination Surge Protection Device (module configuration and voltage as selected)

Please note: DIN rail, distribution board wiring, circuit breakers and installation accessories are not included unless specifically listed above.

Installation & Compatibility Notes

• Confirm whether your board is single-phase (use 1+1) or three-phase (use 3+1) before ordering.
• Confirm your board's earthing system (TN or TT) and system voltage (275V or 385V) before ordering.
• Confirm wiring capacity requirements against your board's cable sizes before installation.
• Installation should be carried out by a suitably qualified electrician in line with local wiring regulations.
• Check the status indicator periodically — a red window means the SPD has operated and must be replaced.

Warranty & Support

This product is supplied with the applicable manufacturer or supplier warranty, subject to correct installation, correct application, and warranty terms.

Zisabo supplies quality plumbing, pump, filtration and electrical products with practical support to help customers choose the correct item for their application. If you are unsure whether this product is suitable, contact us before ordering and our team will assist where possible.

Need help choosing? If you are unsure whether this product is suitable for your board, contact Zisabo with your system voltage, earthing type and phase configuration, and we will assist where possible.