Bell Transformer — Consumer Unit Accessory

Bell Transformer — Consumer Unit Accessory

The Bell Transformer is a compact, DIN rail-mounted transformer that provides a low-voltage output for powering doorbells, chimes and other ancillary devices directly from a consumer unit or distribution board. Designed to occupy a single module width (18mm), this transformer integrates neatly alongside MCBs and RCBOs without requiring a separate enclosure or external power supply.

It eliminates the need for battery-powered systems and provides a permanent, reliable low-voltage supply for wired doorbell installations in UK homes and light commercial premises.

Key Features

• DIN rail mounting — fits directly into any consumer unit or standard distribution board
• Compact 1-module width (18mm) — minimal space required on busbar
• 240V AC input / 8V AC output — suitable for standard UK doorbell and chime circuits
• Integrated protection — built-in thermal fuse for overload safety
• Low-voltage Class III output — safe for doorbell wiring without additional RCD protection on the bell circuit
• No external power supply needed — powered directly from consumer unit busbar
• Suitable for new installations and retrofits in domestic and light commercial properties

Technical Specification

• Class II double-insulated construction
• Supplied Technologies Limited, UK

Installation Notes

The bell transformer must be installed by a qualified electrician in accordance with BS 7671. Isolate the supply before installation. The transformer snaps onto a 35mm DIN rail and connects to the consumer unit busbar via the input terminal. Route the low-voltage output cable to the doorbell or chime location. The output circuit is SELV (Safety Extra-Low Voltage) and does not require additional RCD protection, though the supply-side circuit should be protected by an appropriately rated MCB.