Updating Old Fuseboxes

Posted by on July 12, 2017

In many old homes, fuseboxes (called Consumer Units in the trade) can be vintage artifacts of a bygone era. They can also be incredibly dangerous too. They can be fires waiting to happen. Many customers know this, take a peak, and leave it well alone. People often think it is incredibly expensive to replace them and bring them up to modern standards, yet for a qualified electrician like me it isn’t a particularly difficult job.

One of the benefits up upgrading the consumer unit to a modern one meeting present day standards is that is also an opportunity, in fact a necessity, to test the rest of the wiring that goes into it. Examining the wiring is rather like an archaeological dig. You tend to discover a history of either people who took incredible pride in their job, or as often is the case, a scary series of make do fixes that just about hold together.

A Case Study

I was called to upgrade a consumer unit in Norwich because the wiring had been condemned and someone wanted to live in the house without the worry of it bursting into flames.

The old consumer unit with the case on.

An older style consumer unit, not the worst example I’ve seen either!

A Quick Tour of the Fusebox

First of all, any electrical circuit in a house has live, neutral and earth conductors. Live essentially feeds something (like a lightbulb) shown in the older style red colour, the neutral (black in this case) completes the circuit and runs from the item back to the consumer unit – therefore completing the circuit. The earth (yellow/green) is a protective conductor which in the case of a faulty will take the current away from are of fault back to earth, therefore protecting a person from that current running through them instead.  Whilst modern colours are brown for live and blue for neutral, the principles remain the same.

  • A is the incoming feed (known as meter tails) which comes from your meter into the main fuse in the consumer unit (B). In this instance the main fuse also serves as an RCD (see later) to protect against any faults between the live and earth (e.g. someone hammering  a nail that goes through the earth and live conductors in a cable).
  • C is often called the busbar, this is the backbone of a consumer unit, it is thick piece of copper that links all the live circuits together. Unlike in this example, the busbar has a plastic safety flap over the top protecting from electrical shop.
  • D are the miniature circuit breakers (MCBs), commonly and incorrectly known as fuses. Their sole purpose is to protect the cable they are attached to from overloading and potentially catching fire. When the current drawn by the appliances attached to the circuit excedes the MCB rating, they ‘trip’ and isolate (turn off) the circuit, therefore protecting the cable.
  • E is the point at which the live part of each cable is connected to the circuit breaker. When the circuit breaker is on, current flows though the circuit breaker and into the relevant circuit.
  • F is the neutral bar, the point at which all neutral conductors from all circuits are connected.
  • G is the earth bar, the point at which all earth conductors from all circuits are connected. It is also the point at which the earth coming from the supply is connected, and any other earthing conductors (such as those attached to water pipes) are brought together.

This is just a simple explanation of a domestic consumer unit.

In with the new!

Whilst I am not gong to discuss all the faults with this particular unit, and the faults found within the wiring around the property, needless to say that replacing it requires an electrician to test all the aspects of the installation.

  • Condition of the supply.
  • Condition of the old consumer unit.
  • Condition of all the circuits within the house.
  • Condition of all the fixtures and fittings (sockets, switches, light fittings)

The reason for doing this is to ensure a new consumer unit is not installed whilst faults still remain within the house.

Before commissioning this unit, I first had to fix various problems with the circuits, fixtures and fittings. Whilst all of the circuits were deemed acceptable within parameters laid down, the main ring circuit showed a significant difference to the others, suggesting somewhere there was a minor fault. It took a few days to finally isolate it, but the fault was simply down to a damaged cable (probably down to a workman’s powertool at some stage).

What the Customer Said

Brilliant job! Martin did the job spot on budget, on time and efficiently. He obviously took pride in his work and went way beyond what he was originally called in to do at no extra cost!

If you would like me to look at replacing your consumer unit with one that is safe and meets modern-day standards, do give me a call.


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