Electrical Cable Buying Guide

Electrical Cable Buying Guide: Choosing the Right Cable for Every Job

Choosing the correct electrical cable is essential for safety, performance, and compliance with wiring regulations. Using the wrong cable, underestimating the load, or neglecting proper fixings can lead to overheating, voltage drop, or even fire. Whether you are wiring a lighting circuit, an outdoor garden shed, or a high-power cooker, the right cable, cleats, and glands make all the difference.

 

1. Standard Domestic Cable (Twin & Earth)

Twin and Earth (T&E) cable is the most common choice for indoor wiring in domestic properties. It contains:

• One live conductor (brown)
• One neutral conductor (blue)
• One earth conductor (bare copper or green/yellow sleeved)

This cable is suitable for most lighting, socket, and fixed appliance circuits inside the home.

Common Uses and Sizes

• Lighting circuits: 1.0 mm² or 1.5 mm². Use 1.5 mm² for longer runs or where extra capacity is desired.
• Socket circuits: 2.5 mm² is the standard size for general-purpose sockets. Suitable for computers, TVs, small kitchen appliances, and other domestic equipment.
• Cookers and ovens: Depending on the appliance rating, 2.5 mm², 4 mm², 6 mm², or even 10 mm² may be required. Always check the manufacturer’s power rating.
• Showers: High-power showers may require 6 mm², 10 mm², or larger cables. Overestimating cable size is safer for long runs.

Installation tips:

• Fix cables using suitable clips at recommended intervals.
• Avoid sharp bends; the minimum bend radius should be at least 6–8 times the cable diameter for T&E.
• Do not place cables under tension or kink them.
• For circuits with high load or long runs, consider upsizing the cable to reduce voltage drop.

2. Armoured Cable (SWA) for Outdoor and Heavy-Duty Installations

When running cable outdoors, underground, or in locations where mechanical damage is possible, standard T&E is not sufficient. Steel Wire Armoured (SWA) cable offers protection for both the conductors and the installation as a whole. SWA is strong, durable, and suitable for long-term use in harsher conditions.

Common SWA Uses

• Garden sheds or garages
• Outdoor lighting circuits
• Hot tubs or external appliances
• Underground mains supply runs

SWA cable consists of:

1.    Conductors (live, neutral, earth)

2.    Inner PVC sheath

3.    Steel wire armour (mechanical protection)

4.    Outer PVC sheath for environmental protection

SWA Cable Size Guide

Load / Appliance	Recommended SWA Cable	Notes
Small outdoor lighting	1.5 mm²	For low-current circuits like garden path lights
Standard socket supply / small shed	2.5 mm²	Can handle general appliances and hand tools
Medium-load appliances (cookers, ovens, showers)	4 mm² – 6 mm²	Larger cables needed for higher current or longer distances
High-power appliances / long-distance runs	10 mm²	For heavy-duty equipment, long feeder runs, or multiple sockets

Tip: Always check voltage drop, especially for long cable runs. Even if the appliance’s current is within limits, a long run can cause voltage drop that reduces performance or damages appliances. If in doubt, increase cable size.

3. Cleats and Cable Fixings

Proper mechanical support is essential for safety and compliance. Cleats secure SWA cable, prevent sagging, and protect against accidental movement or damage.

Recommended Cleat Spacing

Cable Size	Cleat Type	Max Spacing (Horizontal / Vertical)
Up to 10 mm²	Standard saddle or roller	600 mm / 900 mm
16 – 25 mm²	Heavy-duty saddle	450 mm / 600 mm
35 mm²+	Roller-type cleats	300 mm / 450 mm

Key points:

• Do not over-tighten cleats; they should support the cable without crushing it.
• Avoid sharp bends; minimum bend radius for SWA is 12 times the cable diameter.
• Use cleats rated for the environment (plastic cleats are fine indoors; metal or UV-resistant cleats are needed outdoors).

4. Cable Glands

Cable glands provide a safe and secure termination for SWA cable. They ensure the armour is properly clamped, the conductors are accessible, and the installation maintains its IP rating.

Common Gland Types

Cable Size	Gland Type	Notes
Up to 10 mm²	Standard SWA compression gland	Suitable for most indoor and outdoor boxes
16 – 25 mm²	Heavy-duty SWA gland	Outdoor or industrial applications
35 mm²+	Oversized industrial gland	High-current appliances or feeders
Any SWA to metal box	Brass or nickel-plated gland	Ensures earth continuity from armour to enclosure

Installation tips:

• Make sure the gland grips both the outer sheath and armour.
• Select a gland with the correct IP rating for the location (IP65 or higher for outdoor or damp areas).
• Tighten compression glands according to manufacturer instructions to avoid damaging the cable.

5. Choosing Cable by Application

Here’s a quick overview of common domestic and outdoor cable applications:

Installation	Recommended Cable	Notes
Indoor lighting	T&E 1.0 – 1.5 mm²	Longer runs or high load may need 1.5 mm²
Indoor sockets	T&E 2.5 mm²	Standard radial or ring circuits
Cooker / oven	T&E 2.5 – 10 mm²	Depends on rating and distance
Shower	T&E 6 – 10 mm²	Check shower manufacturer’s rating
Garden shed / outdoor sockets	SWA 2.5 mm²	Protects against damage and moisture
Outdoor lighting	SWA 1.5 mm²	Low current, long life outdoors
Hot tubs / high-power outdoor equipment	SWA 6 – 10 mm²	Use correct gland and cleats
Underground feeder runs	SWA 2.5 – 10 mm²	Select cable size based on load and distance

6. Additional Considerations

1.    Environment: For damp, wet, or outdoor conditions, always use SWA or outdoor-rated T&E.

2.    Load & Distance: Choose cable size based on the appliance’s current and run length. Oversizing is safer and reduces voltage drop.

3.    Mechanical Protection: Use cleats at correct intervals and avoid unnecessary bends.

4.    Terminations: Always use the correct SWA glands and ensure proper armour earthing.

5.    Compliance: All cables, cleats, and glands should meet BS 7671 and relevant IP standards.

6.    Future Proofing: Consider spare capacity for upgrades such as EV chargers, garden lighting expansion, or additional appliances.