Surge Protective Devices (SPD) are used to protect the electrical installation, which consists of the consumer unit, wiring and accessories, from electrical power surges known as transient overvoltages.

They are also used to protect sensitive electronic equipment connected to the installation, such as computers, televisions, washing machines and safety circuits, such as fire detection systems and emergency lighting. Equipment with sensitive electronic circuitry can be vulnerable to damage by transient overvoltages.The effects of a surge can result in either instant failure or damage to the equipment only evident over a longer period of time.

SPD’s are usually installed within the consumer unit to protect the electrical installation but different types of SPD are available to protect the installation from other incoming services, such as telephone lines and cable TV. It is important to remember that protecting the electrical installation alone and not the other services could leave another route for transient voltages to enter the installation.

There are three different types of Surge Protective Devices:

• Type 1 SPD installed at the origin, e.g. main distribution board.
• Type 2 SPD installed at sub-distribution boards
  (Combined Type 1 & 2 SPDs are available and are usually installed in consumer units).
• Type 3 SPD installed close to the protected load. They must only be installed as a supplement to Type 2 SPD.

What are transient overvoltages?

Transient overvoltages are defined as short duration surges of electricity which occur due to the sudden release of energy previously-stored or induced by other means. Transient overvoltages can be either naturally occurring or man-made.

How do transient overvoltages occur?

Man-made transients appear due to switching of motors and transformers, along with some types of lighting. Historically this has not been an issue within domestic installations but more recently, installations are changing with the advent of new technologies such as electric vehicle charging, air/ground source heat pumps and speed-controlled washing machines have made transients much more likely to occur within domestic installations.

Natural transient overvoltages occur due to indirect lightning strikes most likely to happen due to a direct lightning strike on an adjacent overhead power or telephone line causing the transient overvoltage to travel along the lines, which can cause significant damage to the electrical installation and associated equipment.

Do I have to have SPDs installed?

The current edition of the IET Wiring Regulations, BS 7671:2018, states that unless a risk assessment is carried out, protection against transient overvoltage shall be provided where the consequence caused by overvoltage could:

Result in serious injury to, or loss of, human life; or
Result in interruption of public services and/or damage to cultural heritage; or
Result in interruption of commercial or industrial activity; or
Affect a large number of co-located individuals.
It is also worth checking with your insurance company as some policies may state that equipment must be covered with an SPD or they will not payout in the event of a claim.

This regulation applies to all types of premises which include domestic, commercial and industrial.

Reference – IET

A Residual Current Device (RCD) is a safety device designed to quickly disconnect electrical circuits when it detects an imbalance in the electric current, helping prevent electrical shocks and fire hazards. An RCD is a standalone device that is typically installed at the origin of the electrical installation. It offers protection to a group of circuits or to the entire installation, detecting imbalances in the current flow.

RCD’s & Split Load Consumer Units are now being phased out in place of RCBO’s, mainly due to the combination of earth leakage in modern installations & nuisance tripping. The cost of RCBO’s have come down considerably recently and benefit the installation by combining the functions of an RCD with an MCB into a miniature device. If a circuit trips when protected by an RCBO it does not affect half of the house / installation as it would with an RCD / split load consumer unit, only that individual circuit would be isolated.

An ‘MCB’ (Miniature Circuit Breaker) primarily acts as a circuit breaker, protecting against overloads and short circuits. It is responsible for interrupting the current flow when it exceeds the rated capacity of the circuit – protecting the cabling or when a short circuit occurs. MCBs are commonly used in residential and commercial settings to protect individual circuits and appliances. They can be paired with an RCD where required, in a spilt-load consumer unit to combine overload, short circuit & earth leakage protection. Or simply fit an all-in-one ‘RCBO’ device which contains all of the above in one unit.

RCBO stands for ‘Residual Current Breaker with Over-Current‘. As the name suggests it protects against two types of fault and in essence combines the functionality of an MCB and RCD.

The primary functions of RCBOs are to ensure protection against earth fault currents, overload, and short circuit currents. It is recommended that an RCBO be attached to each separate circuit, meaning that a fault in one circuit will not affect the functioning of the others.

A Distribution Board or DB is generally a consumer unit that is used in larger, more power hungry electrical installations such as industrial and commercial settings. They are often larger than the traditional consumer unit found in your house, although ultimately operate in much the same way.

Distribution boards, will often be Three Phase, used for more demanding applications and larger motors for example

A DB divides the incoming electrical power supply into subsidiary circuits. These circuits are provided with a protective fuse or circuit breaker with the rating depending on the cables size, installation method and length.

A distribution board can feed multiple other DB’s known as Distribution Circuits or sub-main’s

Consumer units are basically the modern and safer version of fuse boxes.

If your house is fitted with an old fuse board / fuse box which is wooden, or has rewireable fuses – it might be time to for you to replacement as it may not have RCD protection for example and modern safety devices. However, just because the fusebox is old does not mean it needs replacing. It is recommended that you have an Electrical Installation Condition Report / EICR carried out to inspect and test your fusebox and the wiring in your home. Contact us today to book an inspection and for advice

Where your installation is on what’s known as PME or TN-CS (Which most of the UK now is) there is a risk of ‘loosing a neutral’ which is outside of your control. This can happen within the electricity network supplying your home. The risk is the installation could rise to a dangerous voltage. To get around this the car chargers we use have ‘Open PEN Detection’ and automatically disconnect in the event of a fault, making them safe to use! This also removes the requirement for an earth rod being installed.

Type 1 plug

Power rating of 3-7kW AC, Single Phase (Slow/Fast Charge):

• Approx 12 miles range per 30 mins of charging
• Only available in single phase
• Less common in modern electric cars
• Has no locking mechanism when the car is connected to supply
• Up to 7kW AC. This socket is typically found on older EVs, such as the original (2010-2017) Nissan Leaf

Type 2 plug (Also known as ‘Mennekes’ connector)

Power rating of 3-42kW AC, Single Phase/Three Phase (Fast Charge):

• Approx 75 miles range per 30 mins of charging
• Becoming the standard European charging cable connector type
• Compatible with both single and three-phase electricity supply
• In-built locking mechanism when connected to the power supply
• Tesla has a 120 kW DC version of type 2
• A fast charger charges at speeds of between 7kW to 22kW AC and is the most common type of home charge point. Fast chargers are found on the public charging network, too. Zap Map reports they are the most easily found charger type in the UK.
• A 7kW fast charger will refill an EV battery in six to eight hours, with a 22kW connection taking three hours. Popular fast charge networks include BP Pulse, Pod Point and the Gridserve Electric Highway.

CHAdeMO plug

Power rating of 50kW DC, Three Phase (Rapid Charge):

• Approx 85 miles range per 30 mins of charging
• Older type of charging cable connector for rapid charging
• Compatible with Japanese vehicle manufacturers
• Most common rapid connector type due to the popularity of the Nissan Leaf
• This connection is favoured by Japanese and Korean car makers. Popular models that use it include the Mitsubishi Outlander PHEV and Nissan Leaf.

Combined Charging System (CCS) plug

Power rating of 50-350kW DC, Rapid Charge:

• Approx 85-200 miles range per 30 mins of charging
• The most versatile rapid charging connector
• Likely to become the most popular DC connector standard
• Enables a higher power rating to support larger ultra rapids chargers
• Up to 350kW DC. The most popular form of rapid or ultra-rapid charging connection, CCS car sockets contain a combined alternating current (AC) and DC port
• Electric cars that use CCS include the BMW i3, Jaguar I-Pace, Kia e-Niro and Volkswagen ID.3

Here are some things to consider when you’re choosing a place for your charge point.

• Do you want the charge point to be hidden or on view? Whether you have a tethered or untethered charge point will make a difference here, you may not want the tethered cable to look like a coiled garden hose on the front of your house
• Where is the charging port on your EV located? Some are easy enough – right on the front, but others are on a side, or even further back where you’d normally have a fuel filler cap
• Factor in the length of the charging cable. Even on a private drive, a cable can present a very serious trip hazard
• The charger will also require access to your home wifi signal to take advantage of the smart tools, such as remote charging and access to off-peak energy tariffs, so it may not want to be at the furthest corner from your router

This depends on the size of your car battery and the speed of the charging point. With a 7kW charging point it takes just under 8 hours to fully charge an electric car with 60kWh battery.

The kilowatt (kW) refers to the power rating of a home charge point and is the maximum amount of power that can be drawn from the point at any one time. A 7kW home charger will charge your car three times faster than a standard three-pin plug. 22kW is for three-phase installations only, generally commercial properties.

In the UK 3-7 kW chargers are the most popular and are widely recommended. Most homes have a single-phase (AC) electricity supply and can support the additional 7 kW load. There are some homes with three-phase (AC) supply that can use a more powerful charger up to 22 kW. We will check that your fuse board has enough spare capacity to support the additional load of a home charging station.