When preparing for a full or partial re-wire, or a new installation, there are lots of decisions to be made. This page provides some useful information about the most common decisions you may be asked to make.
Socket and Accessory Heights
Part M of the Building Regulations lays out some very specific rules regarding the height of electrical fixtures and fittings in a domestic setting. In all new installations, the bottom of accessories should be no lower than 450mm above the finished floor level, whilst the top of accessories should be no higher than 1200mm above the finished floor level.
For existing installations however, the regulations do allow for fixtures and fittings to remain at the same height as they are presently providing the accessibility is no worse than it was before the re-wire.
You can therefore elect to have the fixtures and fittings left where they are, or moved to fit the current building regulations. In some situations you may be advised to move them, in which case it would be advised that their placement complies with the current regulations. An example of such a situation maybe a socket outlet that is currently mounted in or on the skirting board.
There are no rules regarding the height of consumer units, but Part P of the Building Regulations suggests that these should be installed such that the switches are at a height of between 1350mm and 1450mm. This puts them out of reach of young children whilst still being accessible to most adults when they are standing or sitting.
Using modern consumer units, the electrical installation in your home is typically split into two distinct sections. Upstairs and Downstairs, with each section being supplied by a separate fault protection device. Under these conditions however, a fault can take out power to an entire floor. This could increase the risk of injury from trips and falls for the residents if the fault occurs at night and results in a loss of lighting.
This risk can be mitigated by splitting using a different scheme. Typically the property will be split into two sections. The front and rear of the property for example. The front portion (both upstairs and downstairs) is connected to one fault protection device and the remainder is connected to another. In this scenario, a fault in the front lighting circuit won’t affect all the lights on a single floor so the resident will still be able to use some lights upstairs and downstairs.
This could increase the cost of installation slightly due to increased cable usage and added complexity when compared to a straight forward upstairs downstairs split. However, this should be weighed against the benefits it can bring.
RCDs plus MCBs or RCBOs
Most domestic installations will use a combination of residual current devices (RCDs) and miniature circuit breakers (MCBs). With the normal split, a fault on one circuit will cut the power to all circuits supplied by the same RCD as the one on which the fault occurred. This can be inconvenient.
To reduce the inconvenience, you can elect to use residual current devices with overload protection (RCBOs) instead. In this scenario, each circuit is provided with the additional protection of an RCD and the overcurrent protection provided by an MCB in one combined unit. Using these devices means a fault on one circuit will not disrupt power to other circuits.
You don’t have to use a single approach, you can mix and match to best suit your needs and your desire to minimise the inconvenience when a fault does occur.
Cost may also be a factor in this decision as RCBOs are somewhat more expensive than MCBs.
Not all circuits have to be protected by a residual current device (RCD). In some cases you may not want them to be in order to avoid the potential problems when an RCD is tripped. Some typical examples are mains powered smoke alarms, appliances such as fridge freezers or life support or other health related devices.
Today, there are a wealth of accessory styles to choose from allowing you to pick ones that match the styling of the room in which they are being installed, you don’t have to have boring old white. It is worth a word of caution though. Like many other styles and trends relating to home styling, accessory styles can come and go and this can present a problem in the future should you need to replace an accessory due to damage or if you need to add to the installation.
Getting that perfect match for accessories installed a few years ago can be impossible, resulting in mismatch or you having to pay to replace all so they match.
Sticking to plain vanilla white accessories gives a greater chance of finding ones that don’t stand out like a sore thumb if they are replaced or added to.
Neon Lamp Indicators
There is very often the choice of having an illuminated indicator in switches and socket outlets to indicate whether they are turned on or not. Unless there is a compelling reason to have these, my advice is to avoid them. They are typically orange neon lamps. Very simple devices, but over time they can degrade resulting in a loss of illumination or an annoying flickering (which can itself lead to a dangerous situation if people come to rely on the lamp being on to indicate something is turned on). They also make it more difficult to perform testing on the installation as they adversely affect some of the tests required to prove the installation is safe.
With these points in mind, my advice is avoid them where you can and only have them installed if there is a very compelling reason to.