400 & 500 Volt Diazed Fuse-Holders to IEC 60269-3 – Type LD

400 & 500V Diazed Fuse Holders to IEC 60269-3 – Type LD Diazed Fuse Holder | Screw Type Fuse Holder | Screw Fuse Holder | Bottle Type Fuse Holder

Product Introduction

The Lawson Type LD is a complete range of Diazed Fuse Holders, fuse bases, and accessories for use with Lawson Type LD Diazed fuse-links in home, business, and building electrical installations at 400V and 500V a.c. As the original Screw Type Fuse Holder system — based on the distinctive Bottle Type Fuse Holder design introduced by Siemens in 1909 and standardised under IEC 60269-3 — the Diazed system remains widely specified and installed across UK, European, and international electrical networks, particularly in older and heritage installations and in applications where the inherent tamper-resistance and overrating prevention of the Diazed system is required.

The Lawson Type LD Diazed Fuse Holder range covers all standard Diazed fuse base sizes — including DIII, DIV, and DV — in single-pole and multi-pole configurations. Each Screw Fuse Holder base is used in combination with a screw cap carrier that holds the bottle-shaped Diazed fuse-link in place, and a colour-coded gauge piece that physically prevents a fuse-link of higher current rating than the circuit requires from being inserted — a critical safety feature that makes the Bottle Type Fuse Holder system inherently resistant to overrating.

In addition to fuse bases, the Type LD range includes a comprehensive set of accessories: replacement screw caps, gauge pieces in all current rating colours, and surface mounting plates — making it a fully self-contained Screw Type Fuse Holder system for new installations, maintenance, and replacement projects.

Key Features

• Diazed Fuse Holder — complete fuse base, screw cap, and accessory range for the Diazed D-type fuse system
• Screw Type Fuse Holder — fuse-link is held in place by a threaded screw cap carrier screwed into the fuse base
• Screw Fuse Holder design — tool-free fuse replacement using the screw cap mechanism
• Bottle Type Fuse Holder — accepts the distinctive bottle-shaped ceramic D-type Diazed fuse-links
• Covers all standard Diazed sizes — DIII (E33), DIV (R1¼”), DV (R2) fuse bases
• Rated 400V and 500V a.c. — suitable for residential, commercial, and industrial electrical installations
• Colour-coded gauge pieces — physically prevent insertion of a fuse-link with a higher current rating than the circuit permits (anti-overrating protection)
• Current ratings: 2A to 200A depending on Diazed size — covering the full range of domestic, commercial, and light industrial circuit protection requirements
• Compliant with IEC 60269-3 — the international standard for fuses for use by unskilled persons in household and similar installations
• Full accessories range included: replacement screw caps, gauge pieces, and surface mounting plates
• Compatible with Lawson Type LD Diazed fuse-links (gG general purpose, gM motor protection, and semiconductor protection variants)

How the Diazed Screw Fuse Holder System Works

The Lawson Type LD Screw Type Fuse Holder system consists of three main components working together:

1. Fuse Base The fuse base is fixed to the panel, mounting plate, or busbar assembly. It contains the fixed contact at the base and the gauge ring — a colour-coded insert that physically limits the diameter of the fuse-link end cap that can be inserted, preventing a higher-rated fuse from being fitted in a circuit not designed for it.
2. Screw Cap (Fuse Carrier) The screw cap is the removable Screw Fuse Holder carrier component that holds the Diazed Bottle Type Fuse link in position and presses it firmly against the base contact when screwed into the fuse base. The screw cap is unscrewed to access and replace the fuse-link — no tools required. Replacement screw caps are available as accessories for all Diazed sizes.
3. Gauge Piece The gauge piece (also called a gauge ring) is a colour-coded insert fitted inside the fuse base that physically limits the maximum current rating of the fuse-link that can be installed. A gauge piece rated for, say, 25A will only accept a Diazed fuse-link with an end cap diameter equal to or smaller than that of a 25A fuse — preventing a 32A, 63A, or higher-rated fuse from being fitted. This is a fundamental safety advantage of the Diazed Bottle Type Fuse Holder system. Replacement gauge pieces in all current rating colours are available as accessories.

Accessories Available

The Lawson Type LD Diazed Fuse Holder range includes a comprehensive accessories package for installation, maintenance, and replacement:

• Replacement Screw Caps — for all Diazed sizes (DIII, DIV, DV), allowing quick replacement of worn or damaged screw cap carriers without replacing the entire fuse base
• Gauge Pieces — colour-coded inserts for all current ratings and Diazed sizes, enabling the correct anti-overrating protection to be set for each circuit within the installation
• Surface Mounting Plates — for panel and wall surface mounting of Diazed fuse bases in single-pole and multi-pole arrangements

Applications

The Lawson Type LD Diazed Fuse Holder, Screw Type Fuse Holder, and Bottle Type Fuse Holder range is used in:

• Residential electrical installations — consumer unit and distribution board fusing in domestic properties with Diazed fuse systems
• Commercial and light industrial buildings — general purpose circuit protection in commercial premises, workshops, and light industrial units
• Maintenance and replacement — like-for-like replacement of existing Diazed fuse bases, screw caps, and gauge pieces in legacy installations
• Industrial control panels — where the Diazed Screw Fuse Holder system is specified for motor circuit and transformer primary fusing
• European and international projects — the Diazed system is widely used across Europe and internationally, making the Lawson LD range suitable for international project specifications
• Heritage and conversion projects — rewiring and upgrading existing buildings where Diazed fuse systems are already installed and the decision is made to retain the Diazed format

Why Choose Lawson Type LD Diazed Fuse Holders?

The Diazed Bottle Type Fuse Holder system has been in continuous service across the world’s electrical infrastructure for over a century — and for good reason. The physical anti-overrating protection provided by the colour-coded gauge piece system is a design feature that no modern MCB or fuse can match: it is simply impossible to insert a fuse-link of a higher current rating than the gauge piece allows. This inherent safety characteristic makes the Lawson Type LD Screw Type Fuse Holder a trusted choice wherever tamper resistance and overrating prevention are priorities.

Type LD Diazed fuse-links are used to prevent short circuit in home, business and building electrical installations, with the fuse held in place by the screw cap, which is screwed into the fuse base. Lawson Fuses Lawson’s complete accessory range — including replacement screw caps, gauge pieces, and surface mounting plates — means the entire Diazed Fuse Holder system can be supplied, maintained, and serviced from a single Lawson source.

All Lawson Type LD products are manufactured under an ISO 9001 accredited quality management system with test facilities accredited to ISO/IEC 17025, and comply with IEC 60269-3 — the international standard governing fuse systems for household and similar installations.

The Lawson Type LD Diazed Fuse Holder range covers the standard Diazed (D-type) size system, where each size corresponds to a specific fuse-link body diameter, gauge ring dimension, and current rating range:

For full current rating availability by size, please refer to the Type LD Product Information Sheet or contact the Lawson Fuses sales team.

Q1. What is a Diazed Fuse Holder?

A Diazed Fuse Holder is a screw-in fuse holder system designed for use with D-type (Diazed) bottle-shaped ceramic fuse-links. It consists of a fuse base with a fixed contact and a colour-coded gauge ring, a screw cap carrier that holds the fuse-link in place, and the Diazed fuse-link itself. The Lawson Type LD Diazed Fuse Holder range covers sizes DIII, DIV, and DV for 400V and 500V a.c. installations, and is fully compliant with IEC 60269-3.

Q2. What is a Screw Type Fuse Holder?

A Screw Type Fuse Holder — also called a Screw Fuse Holder — is a fuse holder in which the fuse-link is secured by screwing a cap or carrier into the fixed fuse base. In the Diazed system, the screw cap is unscrewed by hand to access and replace the fuse-link, making fuse changes quick and tool-free. The screw-in design also creates a secure, vibration-resistant connection between the fuse-link and the holder — making it a reliable choice for both fixed and light industrial panel applications.

Q3. What is a Bottle Type Fuse Holder?

A Bottle Type Fuse Holder is the informal name for the Diazed fuse holder system, named after the distinctive bottle-shaped ceramic body of the D-type (Diazed) fuse-link it accommodates. The bottle shape — with a wider body tapering to a narrower end cap — is central to the anti-overrating safety mechanism: the diameter of the end cap varies with the current rating, and the gauge piece in the fuse base only accepts end caps up to a certain diameter, physically preventing a higher-rated fuse from being inserted.

Q4. What Diazed sizes are available in the Lawson Type LD range?

The Lawson Type LD Diazed Fuse Holder range covers the three most widely used Diazed fuse sizes: DIII (E33 gauge) for currents up to 63A, DIV (R1¼” gauge) for currents up to 100A, and DV (R2 gauge) for currents up to 200A — all rated at 500V a.c. The complete current rating availability for each size is detailed in the Type LD Product Information Sheet.

Q5. What is a gauge piece and why is it important?

A gauge piece (or gauge ring) is a colour-coded insert fitted into the Diazed fuse base that physically limits the maximum current rating of the fuse-link that can be installed. Because Diazed fuse-links have end caps of varying diameter — larger diameters for higher current ratings — a gauge piece set to, say, 25A will only accept a fuse-link rated 25A or below. This anti-overrating mechanism is a fundamental safety feature of the Diazed Fuse Holder system and is one of the primary reasons the Diazed system has remained in widespread use for over a century. Replacement gauge pieces are available for all current ratings and Diazed sizes in the Lawson Type LD accessories range.

Q6. What voltage rating is the Lawson Type LD Diazed Fuse Holder?

The Lawson Type LD Screw Type Fuse Holder range is rated for use at 400V and 500V a.c. — covering both UK/European standard supply voltages for single-phase (230/240V) and three-phase (400/415V and 500V) electrical installations.

Q7. What accessories are available for the Type LD Diazed Fuse Holder?

The Lawson Type LD range includes a comprehensive accessories package: replacement screw caps for all Diazed sizes (DIII, DIV, DV), allowing worn or damaged carriers to be replaced without changing the fuse base; gauge pieces in all current rating colours for all sizes, enabling correct anti-overrating protection; and surface mounting plates for panel and wall surface mounting of fuse bases in single-pole and multi-pole configurations.

Q8. What is the difference between the Diazed and Neozed fuse holder systems?

The Diazed (D-type) and Neozed (D0-type) are both screw-cap Bottle Type Fuse Holder systems, but they differ in size and voltage rating. The Diazed system uses larger fuse-link bodies (DIII, DIV, DV) and is rated at up to 500V a.c. The Neozed (D0) system uses smaller, more compact fuse-link bodies (D01, D02, D03) and is rated at 400V a.c. — reflecting the modern maximum voltage of European three-phase installations. Lawson supplies both — the Type LD Diazed range and the Type LNZ Neozed range. The two systems use different fuse-link body sizes and are not interchangeable.

Q9. What fuse-links are compatible with the Lawson Type LD Diazed Fuse Holder?

The Type LD Diazed Fuse Holder is compatible with Lawson Type LD Diazed fuse-links — available in gG (general purpose), gM (motor protection), and semiconductor protection variants. The correct Diazed size (DIII, DIV, or DV) and current rating must match the fuse base, gauge piece, and circuit design current. Fuse-links from other manufacturers to the same Diazed standard dimensions are also compatible provided the voltage and current ratings are appropriate.

Q10. How do I order the Lawson Type LD Diazed Fuse Holder and accessories?

The full Lawson Type LD Diazed Fuse Holder, Screw Type Fuse Holder, and Bottle Type Fuse Holder range — including fuse bases, screw caps, gauge pieces, and surface mounting plates — is available through the Lawson Fuses sales team and their network of authorised sales partners and electrical wholesalers across the UK. Contact Lawson Fuses directly for trade pricing, availability by Diazed size and current rating, and technical support for your installation or maintenance project.