Shower circuit design.

Dbat: 
 

Surely the breaker is protecting the cable, not the load. 

The breaker has to protect the cable against fault current ("adiabatic" or “let through” in the case of mcb's and RCBOs) - Section 434.

Depending on the nature of the load, the breaker may  have to protect the cable (and load) against overload current (Reg 433.1.1). Protection against overload current may be omitted if the load is fixed - Regulation 433.3.1(ii) - provided protection against fault current is provided according to Section 434.

Further, OCPDs may be expected to protect a load as well as a cable (both are, according to BS 7671, classed as electrical equipment, and if the load is a fixed item of electrical equipment, it's part of the installation in terms of its selection and erection at least) …  although I understand there is a misconception in the industry about this.

Dbat: 
 

Surely the breaker is protecting the cable, not the load. 

The breaker has to protect the cable against fault current ("adiabatic" or “let through” in the case of mcb's and RCBOs) - Section 434.

Depending on the nature of the load, the breaker may  have to protect the cable (and load) against overload current (Reg 433.1.1). Protection against overload current may be omitted if the load is fixed - Regulation 433.3.1(ii) - provided protection against fault current is provided according to Section 434.

Further, OCPDs may be expected to protect a load as well as a cable (both are, according to BS 7671, classed as electrical equipment, and if the load is a fixed item of electrical equipment, it's part of the installation in terms of its selection and erection at least) …  although I understand there is a misconception in the industry about this.