Cable Sizing
Installation · C&G 2365 Units 203/305 · Premium section
Picking a cable is a chain of checks: start from the design current, choose protection, then de-rate for how the cable actually runs — grouped with others, buried in insulation, passing through hot spaces. The tabulated capacity that survives those has to beat the current the protective device lets through.
Then comes : a cable that carries the current happily can still deliver mains too weak at the end of a long run, so length becomes part of the calculation. BS 7671 sets the limits; the arithmetic is yours.
Our lessons build the method step by step with calculators inline, then drill it with practice questions that change the numbers — because the exam certainly will.
Common questions
- Is there a free Cable Sizing quiz?
- Cable Sizing sits in the Installation section, which is part of TradeTraining Premium — but the app is free to start, sample questions are open to everyone, and the free sections cover the fundamentals first.
- Where does Cable Sizing sit in the City & Guilds scheme?
- Cable Sizing maps to C&G 2365 Units 203/305. On TradeTraining it lives in the Installation section as bite-size lessons with practice questions.
- What factors affect cable sizing?
- The design current, the protective device rating, and the installation conditions: ambient temperature, grouping with other circuits, thermal insulation and the installation method all de-rate a cable's tabulated capacity. over the run length then sets a second, independent limit.