Understanding Your Consumer Unit Domestic Lighting 💡 - Circuit Protection - MCB and RCD In this short video we look at the requirements within a domestic consumer unit for a UK lighting circuit. The circuit needs the correct type of circuit breaker (MCB) either type B, C or D depending on the load characteristics to offer overload and short circuit protection. The circuit also requires addition protection in the form of an RCD rated at 30 mA or less that will also offer earth leakage protection