Surge protection and the 18th edition regulations…

Today I would like to talk to you about Surge Protection and the 18th edition regulations…









There has been a lot of noise in 2019 about the correct use of surge protection devices while conforming to the 18th edition so today I am going to go through the regulations and use my specialist knowledge in surge protection to explain when, where and how SPD’s should be installed.

In the regulations there are a few installations where surge protection must be fitted:

(Page 101, Regulation 443.4)

Where the consequences of over voltage could:

– Cause serious injury or loss of human life.

Here everyone always considers hospitals and doctors surgeries, where in fact this single line covers a lot of the installations that most contractors work on daily. Under this regulation, any board feeding emergency lightning or fire alarm panels must have surge protection installed. This is because if this equipment was to be damaged, it could mean a potential injury to people within the building.

– Damage of public services or cultural heritage.

For public services this could be anything from a train station to a library, or even motorway services. If it can affect a public service an SPD must be installed. For cultural heritage, this is to mainly protect important historical remains from potential damage, especially when dehumidifiers, or other critical equipment are used to prolong the lifespan of historical objects.

– Interruption to commercial and industrial activity.

This one we have just covered in our last article, but is pretty self explanatory.

– Could affect a large number of co-located individuals.

This could be anything from a school to an exhibition centre or even a block of flats. If electrical damage can affect a large group of people, then an SPD must be installed.

When applying these regulations, it is important to understand that the regulations are not retrospective, therefore will only apply if you are installing a new distribution board or making a significant amendment to an existing installation.

For all other installations, either an SPD is installed or there is a risk assessment which can be performed which will give you a risk level, to state if SPD’s are needed in that installation. I will go further in to the risk assessment method in our next article.

The exception is single dwellings, where an SPD can be omitted if the value of the installation is not seen as significant. This is not a very clear regulation. Essentially it means that the contractor must discuss with the installation owner whether they want an SPD installed or not. It is recommended that if you discuss SPD’s with the home owner and they decline to have them installed, that you get a paper confirmation of this, whether that is on the quote itself or in a declaration such as the document available through NAPIT. This will ensure that if any damage is caused in the future, which could have been averted through the use of an SPD, that the contractor will have proof that it was declined by the customer.

That is most of the regulations surrounding the use of SPD’s. The last thing I would like to mention is the mixing manufacturers regulation. Essentially, as an SPD is installed from an MCB and not directly on the busbar system, it does not affect the integrity of the consumer unit. Also as an SPD is a voltage detection device, it does not have a short circuit withstand capacity, such as an MCB, so does not require type testing to any specific manufacturer. With SPD installation, it is very important to keep the cable lengths as short as possible, so by installing the SPD in the consumer unit, you are keeping these cable lengths to a minimum. Therefore, any manufacturer who states that a contractor must use their SPD is using this regulation for commercial benefit, not to enhance the safety and integrity of our electrical systems, which is what BS7671 was designed to do.

Thanks for reading, if you have any more questions please get in touch with our technical support team on 01484 851 747.

Kirsty Johnson, Technical Sales Director

Lightning and Surge protection in Commercial and Industrial installations…

Lightning and Surge protection in commercial and industrial installations









Following on from my previous post on 21st November about Lightning protection in domestic installations we move on today to discuss lightning and surge protection in commercial and industrial installations.

BS7671 states that Surge Protection Devices (SPD’s) must be installed where the consequence of an over-voltage could result in an interruption of commercial and industrial activity, which in most commercial / industrial installations will be the majority of distribution boards.

When considering which device to install, we need to look at where on the electrical supply you are working. If you are working on a main incoming panel, you will need to assess whether the building needs a combined lightning and surge device (Type 1+2+3) to protect against direct lightning strikes. As discussed in the previous article, only buildings which are either fed by an overhead power line or have an external Lightning Protection System (LPS) will need a Type 1+2+3 device, otherwise a Type 2 device is sufficient. If you are working on a sub distribution board that doesn’t feed any external circuits, the device you will need is a Type 2, which will protect against any transient over-voltages.

If you were looking at protecting a whole commercial or industrial installation, rather than just the board you are working on, firstly a device will need to be installed on the main incomer, then any sub distribution boards more than 10 meters away will need their own protection. Unfortunately, surge protection has a limited range of protection, which is limited after a 10 meter radius, and as surges are most often caused inside the electrical installation rather than transmitted from the main incomer, it is important to ensure that the devices are installed as close to the equipment you wish to protect as possible.

If you want to discuss this any further please call our specialist surge team on 01484 851 747.

Lightning Protection in Domestic installations…

Lightning Protection in Domestic installations…

Following on from my post last week about surge protection in domestic installations today I want to talk to you about lightning protection in domestic installations.

Lightning Protection only needs to be installed on a domestic installation when the property is directly fed by over head power lines, or has an external lightning protection system (LPS) on the property.

Having an external LPS on a domestic property is rare, because the LPS system is designed to protect the physical building in a lightning storm. Most domestic properties are deemed not at risk from direct lightning strikes. The LPS is usually cross-bonded to the main incoming panel, so generally when an LPS is struck by lightning, 50% of the energy goes to earth through the earth rods, then 50% of the energy comes into the building via the cross-bond. Please see the photo below.








This is the same principle with overhead power lines, except as the L&N supply come directly in to your incomer, if the overhead line is stuck by lightning the whole lightning impulse is then transferred through to the domestic electrical system.

This is why you need to install a combined lightning and surge device (Type 1+2+3) on the main panel where the LPS system is cross-bonded to, or where overhead power lines are connected to the internal electrical system.

If there are any consumer units more than 10-15 metres away from the main incoming panel then a surge device (Type 2) will need to be installed. This surge device will be taking care of all the surges generated internally to the property.

Please note that a combined lightning and surge device (Type 1+2+3) will not only protect against direct lightning strikes but also internally generated surges too.

If you have any more questions please get in touch with our specialist surge team on 01484 851 747.

Why do we need to fit domestic surge arresters?

Surge protection has made it’s way into the Wiring Regulations over the past few years, which has left everybody questioning the need for surge protection devices, and quite rightly so.


Surges are temporary rises in over-voltage and can also be referred to as spikes. These spikes are happening all the time within a domestic environment, e.g. when lights are turned on, a washing machine / tumble dryer starts up and especially when the power goes off and comes back on again. Now, these short spikes in the voltage will run around the electrical system and degrade the components inside domestic appliances. This basically means that appliances are only lasting a fraction of their lifespan due to seeing surges.


We are not really experiencing any more surges than we did 30-40 years ago, the problem we are having in this day and age is our technology. TV’s in the 70’s / 80’s were huge, they had massive components inside them that could withstand surges, and ultimately they lasted a long time (I can remember my parents having the same TV for 20+ years). TV’s built today are so thin, and they enable you to do so much more than just simply watch TV. These features mean the technology inside these TV’s has to be so much more sophisticated and faster. Technology in itself though is becoming smaller and more sophisticated, and most electrical equipment nowadays has very delicate micro-processor’s inside. These micro processor’s are very sensitive, especially to over-voltages (surges). The surges prematurely degrade these components, which leads to device failure.


In a domestic situation, this means expensive equipment having to be replaced more often than is necessary.


A Typical TV from the 1980’s 











Compared to a TV from 2019











Add up the value of the electrical equipment in your house and you make your own mind up if it’s worth protecting it all for about £60.


Please be aware that the SY2-D is a Surge Protection Device, not a Lightning Device. This means it will not protect your electrical equipment against direct Lightning strikes. You only need to install a combined Lightning & Surge Device if the domestic property is fed directly by overhead power lines, or it has an external lightning protection system on the building (copper tape and earth rods). To read more about Lightning Protection in Domestic installations please look out for our next article, which will be released next week.


To view the technical specifications or purchase the SY2-D please follow this link:

How to choose an SPD

Due to the changes in the 18th edition there has been the sudden appearance of many surge protection experts, so as a company with over 50 years of experience in the surge protection industry, the technical team at Surge Protection Devices Ltd would like to give you some pointers on how to choose an Surge Protection Device (SPD) for your installation.

Types of Protection

When discussing different types of surge protection, there are three main types:

Type What it does Where to use it
Type 1 Protection against direct  Lightning strikes At the mains incomer of any electrical installation where external Lightning Protection is installed, or is fed by overhead lines.
Type 2 Surge Protection At the mains incomer of any building that doesn’t need any lightning protection, and for use on any sub boards more than 10-15 meters from the main panel.
Type 3 End equipment protection On any piece of equipment where a low let through voltage is needed.

The types of surge protection are combined in most units, giving you two main types. Lightning Protection or Surge Protection.

What are we protecting against?

For the majority of installations we are protecting against surges. A surge is a voltage spike, these are very short elevations in the voltage supplying electrical equipment. Surges can be caused by quite a few different factors, such as switching events. In a domestic property this could mean switching on your washing machine, or commercially, all of the computers in an office being turned on at the same time when staff arrive for work, and industrially, generators or machinery that uses a high level of power when turning on. Nearby lightning strikes can also cause surges in the system as lightning can travel a long distance underground interfering with electrical equipment up to 2 miles away. So in most cases we are looking at a type 2 on the main incomer and type 2 on any subsequent sub boards.

What about lightning?

The only time that a direct lightning strike becomes a consideration is if the         building has either an external lightning protection system, or if the building is fed directly by over head power lines. In these two considerations both will cause a lighting strike to be transmitted directly on to the incoming panel of an installation. In these cases we would be looking at a type 1 device on the main incomer and type 2 on any subsequent sub boards.

How surge protection works

When a surge is detected by an SPD, the excess voltage is diverted to earth. The device then resets itself and is ready for the next surge. This whole process takes place in about 25 nano-seconds, so is extremely fast. The supply to the rest of the installation is never disrupted, as its only the over voltage which will be diverted to earth.

How to choose a device

Ok, so now we know what type of surge protection we need, now we need to consider which device. The most important things to consider are:

Is the device suitable for your earthing arrangement?
This is one of the most common issues with SPD installation. The most important consideration is for TT systems, where the device needs to be suitable. Surge Protection Devices LTD provide Devices suitable for every earthing arrangement, and are happy to assist in choosing the correct device for your installation

Is the device protecting both the live & neutral poles?
There are a few devices on the market with may seem inexpensive compared to other devices, but if the device is not protecting both live & neutral, surges may enter your property and bypass the SPD.

What warranty does the manufacturer provide?
This is generally a key indicator of the quality of the components used in the SPD. Surge Protection Devices LTD provide a 10 year warranty with all of our products

Do you feel confident that the manufacturer could assist with any technical information you may need?
With surge protection, you may require some additional information to complete your installation. You will need to have confidence in the manufacturer of the SPD to ensure they can help assist you. Surge Protection Devices LTD are the leading manufacturers of surge protection devices, we have been supporting customers in the U.K. market for many years. We work with leading training organisations to hold seminars around the country to expand the knowledge of surge protection and we also sit on the JPEL panel to aid in the production of the latest regulations.

Is the device from a trusted source?
Are you buying from a reputable wholesaler or distributor? Surge Protection Devices LTD have national accounts with all of the major Wholesalers in the UK, and we also work with many Independent Wholesalers to ensure you are provided with the correct information when you purchase your device.

For more information on any of the devices or would like to discuss your installation further, please give us a call in the office on 01484 851747, or visit our website

Lightning Strikes at a US whiskey warehouse and destroys nine million litres of whiskey{~email~}#JimBeam

Which Device Do I Need?

Here at SPD Ltd we like to make things as simple as possible, so have made a flow diagram that will guide you through a couple of key questions to determine which device you need. This is an excellent reference tool that you can take on site with you so it’s to hand when you need it.

Surge Protection FAQ’S

Please find below a link to a PDF file with some common FAQ’s on. Please feel free to print this out for display.

Surge Protection FAQ

ELEX Exhibitions Video

This year we are exhibiting at all the ELEX Exhibitions all over the country. Here are a list of dates…

14th & 15th March – Event City, Manchester, M17 8AS. Find us on stand number J76.

25th & 26th April – Westpoint Centre, Exeter, EX5 1DJ. Find us on stand number H78.

23rd & 24th May – Yorkshire Event Centre, Harrogate, HG2 8NZ. Find us on stand number F140.

19th & 20th September – Ricoh Arena, Coventry, CV6 6GE. Find us on stand number C33.

7th & 8th November – Sandown Park, KT10 9AJ. Find us on stand number I3.

If you want to find out any more information about these exhibitions please watch the short video below…

Lightning and Surge protection for electrical and electronic systems to the new British and European Standard BSEN62305

Recently introduced standards put equal importance on protecting the electrical installation and electrical equipment as well as the building itself. This focus is because modern electronic components are very small and sensitive to over-voltages. As technology increases, consumer’s demand that the electrical items we use get smaller, which means the components inside are also smaller. The reduction in the size of these components over the years now makes electronic equipment so sensitive to over-voltages. An over-voltage, or a surge as they are generally called are short spikes in voltage, which unknown to most people are occurring all the time. As the components inside the electrical equipment we use are so small they are slowly degraded by these surges, which gradually shorten the lifespan of the equipment. This phenomenon affects everything that is plugged in to power, from your household electronics through to industrial machinery and computers. Many computer systems are now networked and they rely on each other to operate. If one part of the system gets damaged due to lightning or surges, the whole system will not operate. The consequential losses suffered during such events i.e. downtime and lost production, can be very high.

A Type 1+2+3 combined lightning and surge device must be installed if the building is fed by over-head lines or it has an external lightning protection system. When lightning hits the external lightning protection system (or over-head power lines) the lightning travels down the cable to the main incomer of the building. Although the external lightning protection system is earthed, only 50% of the total voltage from a lightning strike will go to earth, the other 50% (possibly up to 100kA) will travel across the cross-bond on to the incoming panel and out onto the electrical circuits in the installation. This creates a massive risk to the property and to any life inside.

The Type 1+2+3 combined lightning and surge device is usually fitted in a separate enclosure and mounted next to the main board. They are wired in parallel to the supply, and can either be fed directly from an existing breaker in the board, or you can install connection blocks off the main board and wire the device into these connection blocks. If the building has sub-distribution boards more than 10 metres away from the incoming panel, these boards will require additional protection. A Type 2 device is usually sufficient here, unless the panels / sub-distribution boards feed external circuits such as car park lighting, CCTV etc. then these should have a combined Type 1+2+3 device fitted as standard.

In all other installations, where the building does not have an external lightning protection system and is fed by underground cable then a Type 2 surge arrester is sufficient. This Type 2 device can sit on the main board, where it will protect all outgoing circuits. If there are any sub-distribution boards 10 metres away from the main board then these will also need protecting with a Type 2 device. The reason for this is because surges can occur from anywhere in a building. Usually we think about the surges coming in from the mains, but generally this is not the case. Only about 20% of surges occur from outside the building. Whereas 80% of surges are generated from within the building, due to things like switching events.

Domestic Installations

Surge Protection is required to be installed under the 18th edition guidelines from January 2019. This is because the surges that have always occurred in our systems now pose a threat due to the increasing use of more sophisticated electrical equipment. As you can imagine, the equipment we use everyday is getting more technical, but also smaller. Which means that the components inside are getting smaller, so more susceptible to damage from any over voltage. The 18th edition states the only instance surge protection may not be installed in a domestic situation is if the value of the surge protection device exceeds the value of the electrical installation or a risk assessment has been carried out to prove the property does not require protection.

Main Incoming Position

Most modern and the latest designed Type 1+2+3 combined lightning and surge arresters will have common and differential mode protection (all mode arresters). This means that these new devices protect not only from phase to earth and neutral to earth, but also phase to neutral and phase to phase. The advantage of an all mode arrester is a very low let through voltage between all conductors, less than 600V. A device of this type will be able to handle direct lightning currents as well as protect sensitive electronic equipment from damages up to 10 metres away.

Sub-Distribution Boards

Type 2 devices commonly referred to as surge arresters are generally fitted at the sub-distribution board position. They take out of the system internal surges from switching events, which can damage sensitive electronic equipment. Any sub-distribution board more then 10 metres away from the arrester at the main incoming position should have a Type 2 device fitted. They have visual indication of status and should be checked regularly to see if they remain active.

Final Circuits

Type 3 arresters are generally fitted to stand alone pieces of end equipment fed from sockets but not exclusively e.g. a fire alarm panel more than 10 metres away from a sub-distribution board, which has a Type 2 surge protection device fitted.