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.

Interesting Facts About Lightning…

If you have been keeping an eye on our Facebook page recently, you will have seen we did a interesting fact a day for 10 days. All the 10 facts can be found here within this post.


Fact One… The Speed of Lightning

While the flashes we see as a result of a lightning strike travel at the speed of light (670,000,000 mph) an actual lightning strike travels comparatively gentile 270,000 mph. This means it would take about 55 minutes to travel to the moon, or around 1.5 seconds to get from London to Bristol.







Fact Two… When lightning strikes a beach

When lightning strikes sand or sandy soil, it fuses together the grains to create a small glass-like tube known as fulgurite. They are not only prized by collectors, they are also of great scientific value in demonstrating past occurrence of lightning storms.








Fact Three… The most lightning-struck location in the world

Lake Maracaibo in Venezuela is the place on Earth that receives the most lightning strikes. Massive thunderstorms occur on 140-160 nights per year with an average of 28 lightning strikes per minute lasting up to 10 hours at a time. That’s as many as 40,000 lightning strikes in one night!



Fact Four… Helicopters cause lightning

Recent research from the Met Office revealed that helicopters can cause an isolated lightning strike. While flying, the helicopter acquires a negative charge, so if it flies close to an area that is positively charged (e.g. hail or the base of a cumulonimbus cloud) it can trigger a lightning strike.








Fact Five… 1,400,000,000 strikes every year

Lightning is one of nature’s most recurrent and common spectacles. Around the world, there are over 3,000,000 flashes every day. That’s around 44 strikes every second.











Fact 6… Lightning destroys trees

Trees can often be destroyed by lightning strikes. When lightning hits a tree, it usually travels just below the tree’s bark where there is a layer of sap and water. This layer becomes instantly heated and expands causing the bark to be blasted off the tree and sometimes splitting the wood.









Fact 7… It can help plants grow

While nitrogen is in the air all around us, for plants to be able to absorb it (a process vital for their growth) they rely on a process called Nitrogen fixation. Although much of this process is done by bacteria and algae, the extreme heat of a lightning strike causes nitrogen to bond with oxygen to create nitrogen oxides which combine with moisture in the air to fall as rain and water plants with nitrate-rich water.



Fact 8… The width of a thumb and hotter than the sun

While the intensity of a lightning strike can make them appear as thick bolts across the sky, the actual width of a lightning bolt is only about 2-3 cm. The average length of a lightning bolt is about 2-3 miles. The charge carried down this small channel is so intense that the temperature of the lightning reaches 30,000 °C – that’s five times hotter than the surface of the Sun.






Fact 9… Volcanic lightning

While lightning storms are impressive in their own right, they don’t quite compare to the spectacle when volcanic eruptions trigger lightning strikes. When an eruption occurs, earth and ash are thrown into the air in a giant plume, colliding to create an electrical charge. In the same way as normal lightning, the imbalance between the plume’s electrical charge and the charge in the atmosphere leads to lightning strikes.








Fact 10… Counting lightning

To tell how far away a thunderstorm is, simply count the number of seconds between the flash of lightning and the boom of thunder that follows. Divide this number by five and this tells you how many miles away you are from the storm (or divide by three for the distance in kilometres).



And finally…

Did you know, until the late 18th century it was believed that ringing church bells repelled lightning so many church bells bore the inscription fulgura frango, meaning ‘I chase lightning’.

During a thunderstorm, bell ringers would run to the bell tower to ring the bells. However, a high tower with a metal bell was in fact about the worst place to be.

Between 1753 and 1786 in France, 103 bell-ringers were struck by lightning and killed, resulting in the custom being banned.

We hope you enjoyed the fun facts about Lightning. Watch out for more information coming soon to our Facebook page and on our website.

These facts are available from The Met Office.

Fitting our Surge Devices into traditional manufacturers mains units

This is a question that will crop up quite a lot this year, especially as Surge Protection gains popularity through the 18th edition of the wiring regulations. We have been asked time and time again over the years about whether contractors are allowed to install our Surge Protection Device into a traditional manufacturers mains unit. We hope this short blog article will clear things up for you.

Most consumer unit manufacturers, quite rightly, won’t guarantee their boards if another manufacturers MCB’s or RCBO’s are fitted inside it. This is generally because the MCB’s are specifically designed to align with their own unique busbar systems and a badly fitting MCB might create a hot spot with a poorly aligned busbar connection.

However, a free standing din-rail mounted device, such as a surge arrester or timer etc. is not connected to the busbar system, it is only wired by the installer with cables, therefore such problems can’t exist.

If the consumer unit manufacturer insists you use their own surge arrerster, this is purely for commercial reasons, as the installer you can decide to fit our surge arrester in any manufacturers board and we will guarantee it for 10 years. Or you can fit our surge arrester in a separate enclosure directly adjacent to the consumer unit. Even with the separate enclosure added, our prices will still be well below the cost of a surge arrester from the traditional manufacturers.

If you would like any more info on this matter please call our dedicated team on 01484 851 747.

Lightning & Surge Device 10651/LED

Lightning Protection – Product Focus – 10651/LED

Last week we discussed lightning protection being mandatory if the building is fed by over-head lines or it has external lightning protection. To follow on from that, in this week’s blog we will be talking about a specific device, the 10651/LED.

Why It’s Installed:

For those that missed our last blog, here’s a quick re-cap on why Lightning protection is installed.

When lightning hits external lightning protection (or over-head power lines) the lighting travels down the cable to the main incomer of a building. Although external lightning protection is earthed, only 50% of the total voltage from a lightning strike will go to earth and the other 50% (possibly up to 100Ka) will travel across the cross-bond on to the incoming panel and out on to the electrical circuits in the installation. This creates a massive risk to the property and to any life inside.

What Is It:

The 10651/LED is a three-phase lightning and surge combined device. This means that it not only protects against lightning strikes, it will also take any surges out of the electrical system. The 10651/LED is a large device (about 8 module width), which contains all the necessary components to ensure that the electrical system is safe from over-voltages and lightning strikes.

How It Works:

As we discussed last week, the lightning will travel down the copper tape (or over-head cable) and on to your distribution board. With the 10651/LED being so big, it is usually mounted in to an enclosure next to the main panel. When the device detects the spike in the system (whether Lightning or a surge), it directs the spike down to earth and re-sets itself. This device works in about 25ms, which is much faster that the RCD will detect anything, meaning that the breakers wont trip and the electrical supply will continue un-interrupted.

How It’s Installed:

As I previously mentioned, the 10651/LED is very large and usually is mounted in an enclosure next to the board, this needs to fit as close to the main switch as possible. From an existing three-phase breaker in the board, take your live cables in to the top of the device. Take a neutral cable from your neutral bar to the neutral terminal on the top of the device. Finally take an earth connection from the earth bar to the bottom of the device, for this connection the cable needs to be less than 50cm in length.

Check out the 10651/LED here.

If you need any advise about which device you need, please use the contact form or call us in the office on 01484 581747.

Lightning & Surge Protection; What is Mandatory?

It’s all very confusing when it comes to trying to work out what’s mandatory and what’s a recommendation when it comes to lightning & surge protection. This week in our fortnightly blog we decided to try and make it all a bit clearer for you.

What is mandatory?


Lightning Protection

Lightning protection is mandatory in certain circumstances;

  • If the building has external lightning protection already installed (copper tape and earth rods)
  • If the building is fed by overhead power lines


  • When external lightning protection is fitted: When lightning hits the external protection it travels down the copper tape to where it will be cross bonded to your incoming panel, where it connects with the earth. The reason for the mandatory requirement of lighting protection, is that only 50% of the lighting impulse will go directly to earth, the other 50% will travel through the cross bond on to the incoming panel and out on to the electrical circuits in the installation. This creates a massive risk to the life and to the property in this installation.


  • When the building is fed by overhead power lines: When lighting hits the power line, we have the same problem as with the external lightning prooverhead power linestection. The lightning impulse will travel down the power line directly on to the incoming panel, where again it will travel out on to the electrical circuits in the installation.

It is more common to see church’s, schools and hospitals with external lightning protection fitted, as these are classed as high risk buildings, especially with them being public places and in most instances tall. It is less common to see domestic dwellings with external lightning protection, however it does happen occasionally. It is more common to see a domestic dwelling with overhead power lines feeding the property.

Surge Protection

Surge Protection, as in type 2 and 3, are not mandatory, although they are strongly recommended it is not a requirement to have them fitted and your electrical system will still come up to standard without them. In our last blog we discussed the reasons why you would want to fit surge protection in your own home.

I hope this has made it a bit clearer for you, if you need any more advice on what sort of protection you need to be either fitting or recommending, please give us a call on 01484 851747 or you can send us an email through our contact form.

Our website has a great product selector page, to find out which device you need please click here.

Thanks for reading, Helen Johnson

Why should you fit a surge arrester in your home?

Domestic surge arrestors are not mandatory, so why are so many people now fitting them?

The reason is money. The cost of a domestic surge arrestor such as our SY2-D is negligible compared with buying a new TV or replacing the electrical items in your house. Do a quick mental calculation of how much your electrical items are worth, your TV, washing machine, cooker, fridge and not forgetting all of the things you plug in to charge, such as phones, tablets and laptops. Now you can see how that bill would quickly mount up if your home was effected by surges.

Surges occur in every electrical system, they can come from your mains power, turning lights on or turning on large electrical items (such as a washing machine). Unlike lightning damage, Surge damage isn’t as easily seen, it won’t be anything dramatic like blowing up or setting on fire as can occur with lightning damage. Surges just slowly degrade all of the electrical components in your electrical system, which will shorten the life span of your electrical items. A TV that should last 5 years could only potentially last 2 years, if it’s seeing continuous surges.

trailing lead surge protection

Many people say “I don’t need to worry about surges, I use those surge protection trailing leads”. The problem with using these trailing leads as your only form of surge protection is that you don’t plug everything in to them, even the most safety conscious person would not think of plugging their washing machine or fridge through a trailing lead. When you start looking at how many of these trailing leads you would need to protect your whole house, can you imagine how much that would cost? Obviously it would be less than replacing all of your electrical goods, but still expensive, especially when you consider that the majority of surge protection trailing leads sold have little or no information on how they actually work or whether they comply with any sort of standards or regulations.


The most efficient and cost effective way to protect a domestic property from surges is a domestic surge arrester. This can be mounted inside (or next to) any consumer unit, its easily wired in with a parallel connection to an adjacent breaker, a connection to the neutral bar and a connection to the earth bar and that’s it, your whole installation is protected from surge’s.

At only £56.44 each nett, the SY2-D provide a complete surge protection solution to your domestic installation for a great price!

For more information on this device, please see below:

For help choosing the best device if you are looking for something different, please see below:


Thanks for taking the time to read this article and if there is anything you need please contact us on 01484851747.

Helen Johnson

New Product!!! Type 1+2+3, 100kA, Full mode protection common and differential

We have added a new product to our range that directly competes with the Furse ESP415M1. This new product provides enhanced protection to BSEN62305 & BSEN61643. The technical specs are listed below…

  • Very low let through voltage between all conductors less than 600V
  • Full mode protection, phase to earth, phase to neutral, neutral to earth
  • Combined arrester Type 1+2+3 can handle lightning currents and protect sensitive electronic equipment
  • Lightning protection Level 1, which is the highest 100kA 10/350µs
  • Three way visual indication of status
  • Remote changeover contacts can be linked to BMS, buzzer, light etc
  • No earth leakage, means RCD, RCCB will not trip
  • Will extinguish follow currents after activation
  • Din rail mountable
  • Manufactured in Europe by market leading company
  • Can be supplied in a metal or polycarbonate IP65 housing for a small additional cost
  • Internal thermal disconnector

Available in three phase: 10811LED or single phase 10812LED.

Surge Protection Devices Ltd are always striving to bring out new, innovative products to add to their collection of over 3,000 products they already have.

If you would like any more information about this product, please contact our technical helpline on 01484851747.