Do I Need To Upgrade My Consumer Unit

WHAT IS A CONSUMER UNIT?

Your consumer unit, commonly known as a fuse box is the main protective device within your property. Its job is to cut the electricity supply in the event of a fault and keep the occupiers safe.

Consumer units have come a long way from the days of fuse wire, with new safety devices being introduced regularly.

WHAT SHOULD A NEW CONSUMER UNIT CONTAIN.

Any newly installed consumer unit must meet the most recent edition of regulations for electrical installations BS7671. In a domestic installation:

1. All circuits must be protected by a 30mA type A RCD, with a very few exceptions.

2. They must contain a surge protection device, unless expressly refused by the client in writing, (See below)

3. They must be fully metallic with self-closing covers to reduce the spread of fire from melting plastic.

4. And in certain circumstances they must contain arc fault detection (AFDD)

WHAT IS AN RCD.

An RCD (residual current device) is a safety device which sits within your consumer unit and monitors for faults. It does this by measuring the amount of power passing through the live conductor against the amount returning through the neutral. When the difference is more than the rating of the RCD it disconnects. All domestic circuits must now be protected by an RCD with a rating of 30mA, this is because it’s deemed to be below the fatal amount a person can receive as a shock.

TYPES OF RCD DEVICES.

 Most RCD devices currently installed in older consumer units are known as RCCD’s and usually there are just one or two units in a consumer unit, meaning that each RCD protects half or all of the installation. This is not an ideal setup as a single fault can affect your entire property. In a modern consumer unit we now use RCBO devices on all final circuits. These devices contain both the MCB (fuse) and RCD in one unit, meaning that a fault is contained to a single circuit and does not affect the rest of the property.

This is to comply with selectivity regulations and keep the maximum allowable earth leakage of any one RCD unit below the 30% maximum. Newly installed RCD’s should also be type A, this regulation was introduced in 2022 to stop the use of older style type AC RCD’s (which have been banned in a number of European countries for many years) as these can be blinded to faults where there is a lot of DC equipment on a circuit, which in modern homes is every circuit.

SURGE PROTECTION

SPD’s are now common within new installations following amendment 2 of BS7671 2019 and should only be omitted if the client give a written consent that the cost of an SPD is less than the possible damage a surge can cause to their electrical installation and equipment. This goes back to when SPD's were an expensive addition, but today they add very little cost to the installation and are fitted as standard.

A Surge can be caused by switch of large generators and more commonly by direct lighting strikes to overhead distribution equipment. This sends a surge of power through the network and can cause damage to sensitive DC equipment within properties, the increasing amount of this type of equipment means damage is more common.

SPD’s monitor the incoming voltage and when a spike is detected they dump the excess back down to earth.

There are three types of SPD.

Type 1 – where your property is supplied via over head power lines and/or has a lightening protection system installed. This must be installed at the origin of the supply.

Type 2 – where your property is fed from underground cables with no lightening protection. These should be at the origin of the supply and on any sub distribution circuits more than 10 meters from the origin.

Type 3 - These are usually installed alongside type 1 & 2, they are usuallay found within equipment such as extension leads.

AFDD

Arc fault detection is the newest safety device on the market. They can detect arcing caused by damaged cables and loose connections on a circuit.

They are more expensive than RCBO's but costs are ever decreasing as technology moves forward.

They are currently only a requirement in high risk situations such as high rise blocks, care homes and houses of multiple occupation. They should also be strongly considered for timber buildings and buildings with thatched roofs. and are onlt required on socket circuits

It's likely that these will become more common in the coming years and could well be a requirement for all installations at some point soon.

CONSIDERATIONS

Replacing a consumer unit is probably one of the most important jobs in your property. It is the safety device that could save you from injury or stop a fire breaking out. Whilst not always necessary, It is a good idea to keep this safety device to the highest most current standards for peace of mind.

When replacing a domestic consumer unit, make sure you choose the right contractor for the job! Cheapest is not best here, you get what you pay for. Good equipment isn't cheap and a good job takes time.

here is a list of everything a good contractor should consider and discuss with you prior.

1. Check and test existing wiring prior to upgrading, this is to check that your existing wiring is in a suitable condition. Adding a new consumer unit which is much more sensitive to faults, to old, faulty wiring is risky as it can cause unwanted tripping. We have seen enough bypassed RCD's in the past because the installer didn't check the wiring first.

2. Check your current earthing and bonding arrangements and advise you to upgrade if necessary. Most older properties typically need bonding to incoming service pipework such as water and gas.

3. Install a consumer unit that meets all the requirement discussed.

4. Carryout a full test of the system once energised and issue you with an electrical installation certificate, clearly detailing the work carried out, and issue a building control notification to confirm the works meet building regulations.