OLD CONSUMER UNIT OR FUSE BOX TYPICAL PROBLEMS

1) What are the typical problems with an old consumer unit or fuse box?

The consumer unit is the brains of our electrical system and contains a variety of parts that require upgrading and replacing over time. In the event of a fault, it is the job of the fuse box or consumer unit to turn the power off to prevent fatal electric shock, earth fault, risk of fire and much more.  

Typical problems with an OLD CONSUMER UNIT or fuse box include:

• RCD tripping 
• Short Circuit Problems 
• Fuses Blowing 
• Fusebox Buzzing 
• Parts Failure
• Overheating
• Main Switch Failure 

2) RCD tripping

Your RCD (Residual Current Device) / GFCI (Ground Fault Circuit Interrupter) / RCCB device is the life-saving device in your fuse box or consumer unit that prevents lethal electric shock from occurring. 

Each of these devices is designed to trip when it senses a problem, the issue is, there can be many reasons that the device will trip and pinning things down can be rather difficult at times. 

Each of these switch devices usually have a test button which should be checked periodically to ensure correct operation and to ensure that the device is working properly. 

3) Short circuit problems

There are devices in your fuse box that are designed to prevent electrical issues from occurring. Short circuit protection (and electrical overload protection) is provided by fuse wire or a cartridge fuse in fuse boxes. In the consumer unit, the Miniature Circuit Breaker (MCB) is the device that we rely on for short circuit protection. 

A short circuit is an electrical fault where Line (HOT) and Neutral have developed a very low or no resistance connection between them. The result of this very low impedance path is a massive electrical fault current that is allowed to flow around the circuit. 

Short Circuits are common with old wiring, old fuse boxes or consumer units, poor electrical installation work and electrical appliances that have gone faulty. 

Where a short circuit occurs INSIDE a consumer unit or fuse box, it is likely that a cable has moved and become damaged or a switch has gone faulty. Where frequent tripping of switches is occurring, have it checked out ASAP.

4) Fuses blowing

Where fuses are blowing in an old fuse board, it is more likely that electrical faults lie on the electrical circuits rather than within the fuse box itself. An infrequent or occasional fuse blowing is not a problem and can be caused by things such as light bulbs that blow on the lighting circuit or the occasional startup of a powerful appliance.

Where fuses are blowing more regularly, then it is likely that some electrical work will need to be carried out to ascertain the issue. It’s more likely that cables will become damaged if switches are continually reset or fuses continually replaced. 

It’s a good idea to have older consumer units or older fuse boxes replaced with more modern fuse boxes or consumer units. Fault finding will need to be carried out before this can be done along with an in-depth electrical inspection to find out the condition of the electrical system.

5) Fusebox buzzing

Where a fuse box is buzzing, there may be electrical problems within the box. There can be some buzzing noises that are actually harmful and are actually part of the normal operation of the electrical system such as a doorbell transformer in normal operation. 

Buzzing noises can indicate that circuits are overloaded, circuit breakers are failing or that there are other electrical issues that require professional intervention by a qualified electrician.

6) Parts failure

As an OLD CONSUMER UNIT ages, the parts are more prone to failure through corrosion, rust or just wear and tear. This can present a problem! Whilst a piece of fuse wire for an older fuse box can be replaced, more modern consumer units have switches and when these fail, replacement parts can be difficult to find.

With a consumer unit switch failure, there are sometimes only second-hand parts available in order to perform a repair. This can be risky due to the unknown origin and operation status of pre-owned parts.

Many emergency electricians will carry a good stock of obsolete parts for fuse boxes and consumer units so if you have a switch failure, try an emergency electrician FIRST. 

Other parts of the consumer unit can also be difficult to source if the unit is over 10 years old. 

7) Overheating 

The number 1 cause of overheating inside a fuse box or consumer unit is without doubt, LOOSE CONNECTIONS. This is often as a result of improper maintenance by a qualified professional. Each consumer unit manufacturer has a specific torque requirement for their electrical connections on switches and other terminals inside the consumer unit. 

Over time, connections can become loose through continued heating and cooling of metals causing expansion and contraction. When combined with supply frequency vibrations, this can create loose connections to occur over the years. 

The result of loose connections is a high resistance as the current flows. The risk of electrical fire is very real in these situations and is more common with higher-powered circuits. 

8) Main Switch Failure

The main switch is the point of electrical isolation for the fuse box or consumer unit. It is often a red isolation switch and its purpose is to disconnect the Line (Hot) and Neutral of the incoming supply to prevent any trip switches or fuses from receiving power inside the fuse box or consumer unit. 

These switches are prone to failure and are one of the most common components that will give you problems in your consumer unit or fuse box. There is an article with more information about the linked main switch here.

9) When is it time to upgrade the unit?

A consumer unit or fuse box should be upgraded every 20 to 30 years. The cost of doing so is relatively minimal when compared to the typical Gas boiler in the home and the lifespan of the modern consumer unit is much longer than that of a boiler making them incredible value!

Failing to have a unit upgraded could lead to expensive repairs should secondary issues occur. An electrical inspection is recommended every ten years in a domestic installation to highlight any hidden defects or electrical dangers that may be lurking unnoticed. 

The electrical inspection should also be carried out before a new consumer unit is added to the installation. A new consumer unit is very sensitive due to all the latest technology within it. The right consumer unit will be chosen by your electrician and should contain a combination of electrical shock protection devices, overload protection devices, surge protection devices and possibly even an arc fault detection device. 

10) How is the upgrade work carried out?

• Pre-installation checks
• Removal of old box
• Labelling
• Division of wiring and circuits
• Installation of new CU 
• Testing and certification

11) Pre-Installation checks

The modern units are incredibly sensitive and as mentioned, checks (Electrical Installation Condition Report) will need to be carried out beforehand on the electrical installation to ensure that the system is suitable for the installation of the new main consumer unit.

This is especially the case where a new consumer unit is to be installed with old wiring.

12) Removal of old box

Removing the old box from the wall needs to be done with care, your electrician will mark each of the wires and label them before installing the new consumer unit. 

13) Division of Wiring and Circuits

Older fuse boxes and consumer units often have had many more circuits added on. There may not have been space for this and it was common to double up on existing circuits rather than installing a new consumer unit.

When the new unit is due to go on, your electrician will split circuits where possible for better convenience and safety in the event of an electrical fault. 

14) Installation of new CU

The new consumer unit is installed, the connections checked and wiring run neatly inside the unit to prevent overheating and confusion for future testing. Where cables need to be extended, they will be extended at this point. 

15) Testing and Certification

Final testing and certification of the unit will be carried out at this point. The electric shock protection devices will be tested with the correct equipment to ensure that they are tripping off in the correct time and under the correct fault current conditions. 
Paperwork will be filled out including an Electrical Installation Certificate.

16) What are the likely costs involved?

Where electrical wiring requires repairing or replacing prior to a consumer unit installation, this could be anything from £300 for minor repairs up to £5000-£9000 for a complete rewire. Once the electrical safety inspection has been conducted, the full costs of any repairs will be known. 

Where the electrical wiring needs to be split into different circuits as in the case of ‘doubling up’ the costs are usually under £400. Its important to talk to your electrician to establish costs once the initial report has been carried out. 

If there are no issues whatsoever, then the consumer unit is likely to cost £600-900 to replace excluding the safety checks prior.

17) Summary

When an OLD CONSUMER UNIT is becoming problematic, an upgraded consumer unit may be the answer. Following the electrical inspection and electrical installation condition report details, the costs will be known for any repairs that need to be carried out to the electrical wiring prior to the upgraded consumer unit being installed. 

Modern standards and wiring regulations state that electrical installations should be checked every ten years. This is not only good common sense but is possibly a way to show your home insurance company that you are correctly maintaining your electrical system. 

Consumer unit replacement is great value and offers additional protection against electric shock occurring along with peace of mind that the electrical system is in good working order.