Connector Strips and Terminal Blocks — 3A, 15A, 30A and 60A Chocolate Block Selection Guide for UK Electricians

Connector strips — sometimes called chocolate blocks — are the original cable joining solution for UK domestic and commercial electrical work. Despite the growing popularity of push-wire connectors, terminal blocks remain indispensable for fixed wiring connections inside consumer units, junction boxes, luminaire terminals, and motor wiring enclosures. This guide covers the four current ratings you need, when to use each, and how to select the correct cross-section for safe, compliant BS 7671:2018+A2:2022 installations.

What Is a Connector Strip?

A PVC connector strip (terminal block or chocolate block) consists of a row of brass or copper barrel connectors moulded into an insulating PVC body. Each barrel accepts conductors from both ends, clamped by a pair of machine screws. The strip is supplied in a standard length — typically 12 or 15 ways — and individual connectors are snapped off to provide the number of poles required. Current rating is stamped on the body and determined by barrel size, screw thread, and PVC grade.

Key properties:

• Current rating — 3A (lighting), 15A (socket circuits), 30A (radials, sub-mains), 60A (cooker, shower supplies)
• Conductor entry — accepts solid and stranded conductor; always strip to the correct depth marked on the barrel
• Screw torque — follow manufacturer's data sheet; over-tightening splits the insulation body
• BS EN 60998 — the product standard for connecting devices for low-voltage circuits; all reputable connector strips carry this marking

Rating Selection — Which Chocolate Block for Which Circuit?

3A Connector Strip — Lighting Circuits

The 3A strip is designed for lighting final circuits up to 6A MCB protection (BS 7671 Appendix 4 Table 4D5A, 1.0mm² T&E). It is the correct choice for:

• Ceiling rose loop-in and loop-out connections (replacing fabric connectors in older work)
• Batten holder and pendant lampholder terminations
• Low-voltage transformer secondary terminals (12V MR16, 12V T&E)
• Smoke alarm base connections (mains supply ≤ 3A)

Do not use 3A strip on socket ring mains, radial circuits, or any circuit protected above 6A — the barrel cannot safely carry the prospective current.

15A Connector Strip — Ring Finals, Radials, and General Wiring

The 15A PVC connector strip is the most-used size in domestic first and second fix. It accepts up to 2.5mm² conductors and suits:

• Ring final circuit (32A MCB) connections inside consumer units and back boxes where WAGO is impractical
• Immersion heater supply (16A circuit, 2.5mm² T&E) at the FCU terminal and immersion head
• Fan and extractor supply terminations inside the ceiling void
• Cooker hood supply at the FSU flex outlet
• Junction box connections for spurs, extensions, and temporary supply splits on site

The 15A rating covers 2.5mm² conductors at ambient temperatures up to 30°C (BS 7671 Table 4D5A). At higher ambient temperatures, apply the correction factors from BS 7671 Appendix 4.

30A 12-Way Terminal Block — Sub-Mains, Consumer Units, and Distribution

A 30A terminal block rated to 30A (and typically 6mm² max conductor) is the standard choice for:

• Sub-main distribution points — connecting the meter tail to an outbuilding consumer unit
• Consumer unit busbars where a separate terminal is required for a dedicated circuit (e.g., EV charger supply, CCTV dedicated circuit)
• Motor control wiring inside isolator enclosures (control circuit up to 6mm²)
• Bonding connections in airing cupboards and plant rooms where an earth bar is not fitted

The 12-way format allows a single terminal block to distribute from one incoming conductor to multiple outgoing circuits inside a metal enclosure. Always fit the appropriate IP-rated enclosure and verify the conductor is rated for the prospective fault current at the point of installation.

60A 25mm² Connector Strip — Heavy Duty Supplies

The 60A single-block connector is designed for large conductor cross-sections up to 25mm² and covers:

• Cooker supply connections (40–45A circuit, 6mm² or 10mm² T&E) at the cooker control unit or the cooker tail terminals
• Electric shower supply (40–50A circuit, 10mm²) at the back of the shower enclosure — always isolate at the consumer unit before opening
• Single-phase EV charge point supply (32A, 6mm² T&E or SWA) at the charger input terminals
• Generator or temporary supply connection on site (always via lockable isolator)

At 25mm², conductor preparation is critical: strip exactly to depth, ensure no insulation under the screw, and verify torque with a calibrated torque driver. Loose connections at high current cause localised heating, arcing, and potential fire.

How to Make a Safe Connector Strip Connection — Step by Step

1. Isolate and prove dead — use a calibrated voltage indicator (GS 38) at all terminals before handling.
2. Snap off the correct number of poles — cut through the PVC body with a sharp knife or snap at the moulded break points.
3. Strip conductor to correct depth — use the gauge marked on the terminal body. Over-stripping leaves bare conductor exposed; under-stripping means only insulation enters the barrel.
4. Insert conductor fully — push until the conductor shoulder contacts the barrel mouth. For stranded conductors, twist clockwise to consolidate strands before insertion.
5. Tighten to correct torque — check the manufacturer's data sheet. A typical 15A block requires 0.5–0.6 Nm on the terminal screws. Use a calibrated torque screwdriver on 30A and 60A terminals.
6. Tug-test each conductor — apply a firm pull (3–4 kg for 2.5mm²) to confirm the conductor is clamped. Any conductor that pulls free indicates an under-torqued or incorrectly inserted connection.
7. Record on EIC/MIC — if the connection is within a notifiable installation, record the terminal type and conductor cross-section on the Electrical Installation Certificate (BS 7671 Part 6).

Connector Strips vs Push-Wire Connectors

WAGO and Q-NECT push-wire connectors have largely displaced chocolate blocks for junction box and lighting connections due to their speed and reusability. However, connector strips retain advantages in specific applications:

• Fixed enclosures — inside a consumer unit or motor isolator, a screw terminal provides a mechanically secure, vibration-resistant connection that push-wire connectors cannot always match.
• Large conductors — push-wire connectors are typically limited to 6mm². For 10mm² and above, connector strip or DIN rail terminal blocks are the practical choice.
• Cost — a 3A or 15A strip
• Inspection evidence — screw-terminal connections are more straightforward to verify with a tug-test during EICR periodic inspection.

BS 7671:2018+A2:2022 and Regulation 526

Regulation 526 of BS 7671 requires that every connection in a wiring system shall be accessible for inspection, testing, and maintenance unless the connection is between a cold tail and heating element, or in a compound-filled enclosure. Connector strips installed inside junction boxes, back boxes, and consumer units meet this requirement provided the enclosure can be reopened without damage. Connector strips must not be buried in plaster or enclosed in inaccessible voids — if a permanent, hidden connection is required, a maintenance-free connector (Reg 526.3) with the appropriate certification is needed.

Selecting the Right Strip for the Job — Quick Reference

Recommended Products

3A PVC Connector Strip

The standard 3A chocolate block for domestic lighting circuits. Accepts 1.0mm² solid or stranded conductor. Snap-off individual terminals as needed. PVC insulation is flame-retardant. Suitable for ceiling rose, batten holder, and smoke alarm terminations on circuits up to 6A MCB.

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15A PVC Connector Strip

The most-used size for domestic ring final circuits, radials, FCU outputs, and immersion heater supplies. Accepts up to 2.5mm² conductors. Full-length strip can be snapped to any length. PVC body meets BS EN 60998 flame-retardancy requirements. Suitable for socket ring mains (32A MCB), lighting radials (16A), and fan spurs.

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Knightsbridge 30A 12-Way Terminal Block Natural

A quality 12-way terminal block rated to 30A for sub-main distribution, consumer unit connections, and motor control wiring. Each pole accepts up to 6mm² conductor. The 12-way format allows one block to serve an entire distribution point. Clear natural PVC housing allows conductor inspection without removal. Knightsbridge quality with BS EN 60998 compliance.

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ProFix 60A 25mm² Connector Strip — Single Block

Heavy-duty single-block connector rated to 60A for cooker supplies (10mm² T&E), electric shower circuits (10mm²), and single-phase EV charger inputs (6–10mm²). Accepts conductors up to 25mm². Single-block format is ideal where only one connection is needed — no unused poles to cover. ProFix quality for demanding trade applications where secure, high-current connections are critical.

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