18th Edition
21/11/19 19:58
I've recently been on a three day course to get my skills updated to the 18th Edition wiring regulations. It is possible to study and simply take the exam in order to achieve the new requirements for electrical installers although I chose on this occasion to study at a training centre. The main reason I did this is that the 18th Edition has a few new items that are causing a bit of a stir in the electrical world and I wanted to study as part of a group so that we could discuss these changes and see how other installers are interpreting these new regulations.
It's worth noting that the 18th Edition regulations fully came into effect in January 2019, and although I've been working to the new regulations (a prerogative we have to allow us the time to study) , I have only recently taken the exam.
Some of the main changes causing confusion are as follows:
1. SPDs or Surge protective devices. These are additional modules housed within the main consumer unit or often sited in another enclosure next to the existing board. These are designed to mitigate electrical over voltages from an external influence that may occur within the electrical installation originating . In short, this is basically all about lightning strikes and preventing damage to some of the more sensitive electrical items we now have within our homes. That's not to say it isn't about preventing fires as well, it does also help against that. To be clear, we aren't talking about a direct strike on the property here, we are talking about a nearby strike that can introduce a surge into the property. These devices mitigate the surge by 'dumping' the over voltage to earth so as to keep the nominal voltage in the property as close to the usual 230v as possible. The confusion around these is in fact when it's appropriate to install them. I understand why it is causing confusion as the method for calculating the need for such a device is, in my opinion rather arbitrary. However, I personally think that installing these devices when fitting a new consumer unit in a domestic dwelling is in the main part a good idea. The additional cost of the components vs the possible loss of equipment due to damage makes it such that to not install them would be unwise. (Although I do always give my customers an informed choice on these matters and some do in fact opt against it). There are circumstances where I would definitely install them, and that's in rural locations, especially those with overhead power supplies.
2. AFDDs or Arc fault detection devices. These are also additional component that are installed within the consumer unit and are designed to 'trip' if an arc fault is detected. That's the kind of fault that can occur at loose connections within an installation for example. Not all arcs are detected though, as by design, any switch that turns on an off a mains voltage will at the point of switching cause a tiny arc at the point that the contacts are just making or breaking. This is normal arcing and the device is clever enough to ignore these. It will however trip when a loose connection is causing a heat build up due to a fault producing around 1Kw of power. That's quite an arc occurring at that point and is likely to cause some localised burning, or worse still a fire. The issue around whether to install these or not, is that they are currently prohibitively expensive, sizeable, required for every individual circuit and also difficult to source! While I think these are fantastic devices, and would be a major advantage in all installations (electrical fires are still a big risk), until they come down in price and are incorporated into the current RCBOs that we use, then they won't be getting installed in a normal setting.
3. RCDs or Residual Current Devices. These aren't new; they are the device that detects a leakage of current to earth caused by a fault and trip out to prevent electric shock to those in contact with a live part. What is new however are the types of RCD being manufactured and the requirement to use certain types in certain situations. Nowadays we have far more appliances in our house that use an element of DC power as well as the AC supply power. A normal AC type RCD will not necessarily trip effectively if a fault occurs on a DC part of an appliance whereas a type A device will (as well as tripping on an AC fault). I feel that there is no benefit in installing the older AC type RCDs anymore, although many manufactures have yet to flood the market with A type RCDs until (I think) they have sold all the old stock of AC type ones. I expect a reasonably fast uptake on A type RCDs once they are readily available. There are other new types of RCD out there now too, but I won't go into those here.
4. Split load RCD boards vs RCBOs. RCBOs are devices that incorporate an RCD and an MCB (mini circuit breaker) in one device. This allows for each circuit to be protected individually against earth faults. Under the 17th edition regulations it was common practice to install a consumer unit with two RCDs within (split load board). One of these RCDs protected half the circuits, and the other, the other half. This meant that if a fault occurred on a circuit on one half of the board, all circuits on that half of the board would trip out when the controlling RCD tripped. While this could be somewhat annoying, it was done in the main for cheapness (RCBOs were expensive) but had the disadvantage that half the house tripped out. This was still better than under the 16th edition when only one RCD was used on all socket outlets and as such when that one tripped, all sockets stopped working. In those days lights weren't protected by RCDs so they would have stayed on. The 18th edition now states (in a roundabout sort of way) that there is a case for installing RCBOs to each circuit rather than split load boards. This is because much of our modern equipment in a house normally leaks a certain amount of current to earth. If only 2 RCDs are used then it's possible that many pieces of equipment could leak enough current to earth to cause nuisance tripping which would be a pain! By controlling each circuit with its own RCD (in the form of an RCBO) would help to reduce the chances of nuisance tripping. Given that RCBOs have recently come down in price recently I think these are likely to be installed far more often than they currently are. Personally, from my own testing, I think it's unlikely that the nuisance tripping on a split load board is very likely in a domestic dwelling, however, I always offer RCBOs as an additional option when replacing a consumer unit nowadays.
There are many other changes in the 18th Edition but the above appear to be those that are causing most uncertainly as to how we go forward. This of course is only my take on them, but I hope it's helped you to understand those changes.
It's worth noting that the 18th Edition regulations fully came into effect in January 2019, and although I've been working to the new regulations (a prerogative we have to allow us the time to study) , I have only recently taken the exam.
Some of the main changes causing confusion are as follows:
1. SPDs or Surge protective devices. These are additional modules housed within the main consumer unit or often sited in another enclosure next to the existing board. These are designed to mitigate electrical over voltages from an external influence that may occur within the electrical installation originating . In short, this is basically all about lightning strikes and preventing damage to some of the more sensitive electrical items we now have within our homes. That's not to say it isn't about preventing fires as well, it does also help against that. To be clear, we aren't talking about a direct strike on the property here, we are talking about a nearby strike that can introduce a surge into the property. These devices mitigate the surge by 'dumping' the over voltage to earth so as to keep the nominal voltage in the property as close to the usual 230v as possible. The confusion around these is in fact when it's appropriate to install them. I understand why it is causing confusion as the method for calculating the need for such a device is, in my opinion rather arbitrary. However, I personally think that installing these devices when fitting a new consumer unit in a domestic dwelling is in the main part a good idea. The additional cost of the components vs the possible loss of equipment due to damage makes it such that to not install them would be unwise. (Although I do always give my customers an informed choice on these matters and some do in fact opt against it). There are circumstances where I would definitely install them, and that's in rural locations, especially those with overhead power supplies.
2. AFDDs or Arc fault detection devices. These are also additional component that are installed within the consumer unit and are designed to 'trip' if an arc fault is detected. That's the kind of fault that can occur at loose connections within an installation for example. Not all arcs are detected though, as by design, any switch that turns on an off a mains voltage will at the point of switching cause a tiny arc at the point that the contacts are just making or breaking. This is normal arcing and the device is clever enough to ignore these. It will however trip when a loose connection is causing a heat build up due to a fault producing around 1Kw of power. That's quite an arc occurring at that point and is likely to cause some localised burning, or worse still a fire. The issue around whether to install these or not, is that they are currently prohibitively expensive, sizeable, required for every individual circuit and also difficult to source! While I think these are fantastic devices, and would be a major advantage in all installations (electrical fires are still a big risk), until they come down in price and are incorporated into the current RCBOs that we use, then they won't be getting installed in a normal setting.
3. RCDs or Residual Current Devices. These aren't new; they are the device that detects a leakage of current to earth caused by a fault and trip out to prevent electric shock to those in contact with a live part. What is new however are the types of RCD being manufactured and the requirement to use certain types in certain situations. Nowadays we have far more appliances in our house that use an element of DC power as well as the AC supply power. A normal AC type RCD will not necessarily trip effectively if a fault occurs on a DC part of an appliance whereas a type A device will (as well as tripping on an AC fault). I feel that there is no benefit in installing the older AC type RCDs anymore, although many manufactures have yet to flood the market with A type RCDs until (I think) they have sold all the old stock of AC type ones. I expect a reasonably fast uptake on A type RCDs once they are readily available. There are other new types of RCD out there now too, but I won't go into those here.
4. Split load RCD boards vs RCBOs. RCBOs are devices that incorporate an RCD and an MCB (mini circuit breaker) in one device. This allows for each circuit to be protected individually against earth faults. Under the 17th edition regulations it was common practice to install a consumer unit with two RCDs within (split load board). One of these RCDs protected half the circuits, and the other, the other half. This meant that if a fault occurred on a circuit on one half of the board, all circuits on that half of the board would trip out when the controlling RCD tripped. While this could be somewhat annoying, it was done in the main for cheapness (RCBOs were expensive) but had the disadvantage that half the house tripped out. This was still better than under the 16th edition when only one RCD was used on all socket outlets and as such when that one tripped, all sockets stopped working. In those days lights weren't protected by RCDs so they would have stayed on. The 18th edition now states (in a roundabout sort of way) that there is a case for installing RCBOs to each circuit rather than split load boards. This is because much of our modern equipment in a house normally leaks a certain amount of current to earth. If only 2 RCDs are used then it's possible that many pieces of equipment could leak enough current to earth to cause nuisance tripping which would be a pain! By controlling each circuit with its own RCD (in the form of an RCBO) would help to reduce the chances of nuisance tripping. Given that RCBOs have recently come down in price recently I think these are likely to be installed far more often than they currently are. Personally, from my own testing, I think it's unlikely that the nuisance tripping on a split load board is very likely in a domestic dwelling, however, I always offer RCBOs as an additional option when replacing a consumer unit nowadays.
There are many other changes in the 18th Edition but the above appear to be those that are causing most uncertainly as to how we go forward. This of course is only my take on them, but I hope it's helped you to understand those changes.