A Guide To Understanding Residential Electrical Consumer Units

A consumer unit, described with the obsolete term fuse-box, is the main unit where all the KwH and Kw pass through to enter into the residential property. Almost every consumer knows where it is located on their property but very few people would know why it exists and how to use it. The consumer unit is the first point where electricity enters from the electricity meter into a residential property. The role of the consumer unit is to methodically circulate electricity all through the property with the help of circuit breakers, residual current devices and main switches. Let’s look at each one of these devices in further detail.

Circuit Breakers & Their Performance

Circuit breakers manage specific electrical circuits within a property and they can go off to prevent the loss of electrical circuits or devices on the circuit. A circuit breaker can locate faults within the circuit they are managing and stop the flow of electricity. Miniature circuit breakers (MCB) may be installed with the electrical outlet on each appliance and there will also be circuit breakers for an entire area of the house.  Some of the cases when a circuit breaker will trip or switch off is during an overcurrent or an overload, so let’s look at what each of these terms means.


An overcurrent is when there is a failure in a circuit of any kind. One kind of circuit failure is when a live wire gets loose and accidentally touches the earth or neutral wire. This kind of situation can be referred to as an overcurrent and the circuit will automatically trip at the circuit breaker. 


An overload occurs when there is an unnecessarily excessive number of appliances plugged into the same circuit. The key to knowing when there are too many devices plugged in is when the number of appliances and the electricity they consume is more than the rating of the miniature circuit breaker. For example, you plug an extension wire in an electrical outlet and all of the sockets on the extension wire are full and each of the devices connected have high electrical consumption. In such a case, there is a high likelihood that the electricity consumption of the number of appliances is higher than the miniature circuit breaker reading and the circuit will trip or overload. 

Main Switch

The main switch controls the supply of mains electricity to the consumer unit from the meter and from the consumer unit to the rest of the property. When viewed from outside there will be a label of ‘Main Switch’ on this panel. The main switch is sometimes also referred to as an isolator. The reason for this is because, when the main switch is turned off, it will isolate the entire circuit connected to the consumer unit from the electrical mains. The main switch will usually have a 3 phase labelling system where L1, L2 and L3 are the three phases that supply power to the circuit. The main switch will also have a path to electrically ground the complete circuit, known as a ‘neutral wire’. 

The main switch is switched off when it is in the 0 position, this indicates that the main supply is disconnected from the circuit and to the consumer unit. The main switch is switched on when it is in the 1 position, this indicates that the main switch is delivering electricity to the consumer unit from the main supply.

Written by Frederick Jace

A passionate Blogger and a Full time Tech writer. SEO and Content Writer Expert since 2015.

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