Free notes
Cable types and marks of conformityGrey or white twin and earth. Does it matter?
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The question at the end: Grey or white twin and earth. Does it matter? The answer is in the notes below.
The notes
Exactly as they are on the site.
| Cable | What it is / where it's used |
|---|---|
| Single core | One insulated conductor, e.g. a 10 mm² green/yellow bonding conductor or a 16 mm² earthing conductor. "Single core" means one cable, not one strand. |
| Twin and earth (T&E) flat, multicore, PVC/PVC, 70 °C | The standard domestic cable. 6242Y has a grey sheath. 6242B has a white sheath and is low smoke zero halogen (LSZH / LSF): less, lighter smoke in a fire, but harder to strip. Grey has a chalky powder inside so it strips easily, which is why most sparks prefer it. |
| Flex | Flexible cable with many fine strands, for appliances and pendants |
| MICC | Mineral insulated copper clad: copper sheath with magnesium oxide powder inside. Very tough and expensive, but moisture from sweaty hands or breath on the ends ruins it. White sheath = emergency lighting (e.g. listed buildings, schools, churches). Red sheath = fire alarms. |
| SWA | Steel wire armoured, with 3, 4 or 5 cores. Used commercially and industrially, and for outside sockets, lights and outbuildings. The armour can be used as the CPC. It's not the same as the DNO supply cable. |
Marks of conformity show a product meets the required standards:
- CE is the EU mark.
- After Brexit, UKCA is used in Great Britain and UKNI in Northern Ireland.
- You'll also see BASEC (cables), ENEC, BEAB and the Kitemark.
Electrician's Guide to the Building Regs · 2.2.2 Conformance to equipment standards: UKCA / UKNI marks · p.35
A common sight: T&E draped loosely across loft joists with a single clip. It's ugly and poor workmanship, but it isn't against the rules, because it's clipped direct. A better job would drill through the joists (following Part A) or clip at every joist.
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