Modern consumer unit
Consumer Unit Replacement Edinburgh
The consumer unit is where the mains power is delivered to the various electrical circuits in the building and, as a result, the electrical accessories such as sockets, lights, etc. after passing through the electrical meter. Selecting the right consumer unit for your needs and the application is essential. We are available to help you select the greatest consumer unit, comprehend how it works, and install it.
The electricity must be shut off for a few hours before installing a new consumer, and each circuit must be connected to the proper protective device. Before and after powering up, extensive electrical testing is carried out, and the results are recorded in an Electrical Installation Certificate. The completed project is given to the client and also reported to building control.
!Therefore, it is essential that a qualified electrician who is a part of a competent person’s scheme instals the consumer unit. (eg. NICEIC).!
When to replace a consumer unit?
As the location where circuits are protected (with fuses or MCBs (Miniature Circuit Breakers)) and can be isolated, every home will either have an antique fuse board or a consumer unit (ie turned off). So when should a consumer unit be changed? Why would you replace the consumer unit? Why alter it if the previous one has served its purpose thus far? There are a number of factors to consider:
✓ It’s possible that you had an electrical installation condition report done, and the study suggested replacing the consumer unit and fuse board. You can ask the electrician who performed
the electrical test and inspection if you are unsure of the reason.
✓There are certain significant distinctions between a consumer unit and a fuse box that you should be aware of if you have a fuse board, where the circuits are protected by fuse wire rather than MCBs.
✓ You will require a new consumer for any newly constructed outbuildings, such as a garage, shed, or outhouse. The same is probably going to be true if you add an annex or an extension to your home. Rather than extending several existing circuits to the new locations, it is always preferable to run in a single new supply cable to the new area and feed new circuits out from there.
Why upgrade the consumer unit ?
In some cases, even if you already have a consumer unit (like MCBs), it is still appropriate to ponder why you would want to update it. Here are a few of them:
✓ The consumer unit may not have enough ‘ways’ to accommodate some new circuits being added to the installation.
✓ The MCBs may be very old and deteriorating.
✓ There may be no RCD protection on the consumer unit.
✓ The consumer unit may be damaged, not be securely fixed or have an inappropriate IP rating (ie large holes allowing possible electric shock for prying fingers).
✓ You are having new circuits run in the house and want to be sure all the associated electrical installation is new and complies with the latest regulations.
✓ For some older consumer units if you require a new circuit breaker (MCB) or a RCBO (residual current breaker with over-current) the manufacturers sometime charge an exorbitant amount to make it more cost effective to replace the whole consumer unit. Which, to be honest, is the better option for you.
Which consumer unit is best?
Customers frequently ask me the type of consumer unit I require. What consumer product should I purchase? Let me ask you a few questions in order to get the best solution::
- What location will the consumer unit be in? (Are you home? within the garage? Outside?))
- How many circuits must it support?
- Would you prefer a single circuit tripping off rather than several in the case of a circuit fault?
- Which do you value more: quality or budget price?
- Do you need additional security measures like SPDs and AFDDs?
To ensure you have the solution to the query “what consumer unit do I need for my house?,” we can offer guidance to help you with the aforementioned questions. What works best for one client may not always work best for another.
Try to buy the most expensive consumer unit you can afford.
Spending more money on a consumer product will result in higher-quality board components. Why save costs when the MCBs and RCDs could save your life?
Cheap consumer goods are frequently considered to be “nasty.” The consumer units can be challenging to install, and the breakers may stop working reliably. They may also not fit properly in the areas that are designated. In most cases, it is preferable to let the electrician who will be installing the board make the purchase. Over the years, they would have installed a wide variety of sorts and learned which ones are pleasant to install (which implies less labour expense for you). They typically stick with those. Therefore, you will have a tidy and expertly installed consumer unit because they will be quite knowledgeable with the finest way to install that product.
Remember that metal consumer units, which are better at containing the spread of a fire, are required for all newly installed consumer units under the most recent wiring standards (18th edition). Therefore, if you purchased a “so-called” bargain for a plastic consumer unit, you won’t be able to install it unless it is housed in a sizable metal enclosure (which may cost you more than a metal consumer unit!)
MCB’s or RCBO’s?
Consumer units in the modern era come in two main shapes:
1. Dual or split load RCD consumer units.
2. Consumer units RCBO.
Let’s start by addressing the question of why a split load consumer unit (or why a dual RCD consumer unit)?
In this case, the consumer unit has two RCDs, each of which can isolate power to half of the circuits, in addition to a main switch to isolate power to the entire consumer unit. This means that all of the circuits and MCBs that those RCDs are safeguarding will be without power if one of them trips off due to a problem. As you may imagine, if you lost electricity to half your home’s circuits, this would be extremely disruptive.
The RCBO consumer unit, on the other hand, contains a main switch once again, but each circuit is secured by an RCBO (which is in effect an RCD and MCB in one unit). Only the one RCBO protecting the circuit with the problem would go off in a fault condition. minimising disturbance while you wait for the electrician to identify the problem.
Although RCBO consumer units are more expensive, they are a far superior choice for the reasons mentioned above.
Consumer unit without RCD protection
A consumer unit without RCD protection may occasionally be utilised in an application legally. An example of this may be a shed that needs a lighting and socket circuit. This is supplied by an armoured cable, perhaps from a circuit on the house’s main consumer unit. The consumer unit in the shed doesn’t require a second RCD if the supply circuit on the main consumer unit is RCD protected and the necessary disconnection times are observed. In fact, having two RCDs on the same circuit may be a hassle because you never know which one will trigger in the case of a problem. (In some cases, you can utilise various RCD ratings to prevent this; it is outside the scope of this essay.)
Consumer unit with SPD’s and consumer unit with AFDD’s
Improvements and advances are made to boost electrical safety as wiring standards are gradually expanded throughout time. Surge protection devices (SPDs) and arc fault detection devices are two such enhancements that have recently been made (AFDDs).
To safeguard all the circuits downstream from significant voltage surges (or spikes), such as lightning strikes or voltage surges, surge protection devices are installed in the consumer unit. This is especially important if there is expensive, delicate electronic equipment present that could be harmed by higher voltages. These gadgets will be protected by a consumer unit with surge protection, which will turn off the power before it reaches the circuits in the building.
Devices that detect arc faults are meant to reduce the risk of fire in a fixed installation’s final circuits as a result of persistent arc fault currents. Although a spark-producing defect in a circuit wouldn’t trip the MCBs or RCDs, it could still pose a serious threat.
The 18th edition wiring standards do not require the use of either of these devices, but they are available if you want to add that level of security to your installation.
Allow for more circuits than you have
In order to future-proof a new consumer unit as much as possible, make sure there are a few more ways on the board. So, for instance, if the home uses 8 circuits, I would advise installing a 10 way board. If a log cabin is built in the garden, there is a spare place for an MCB for the circuit for the log cabin.
Which consumer unit to buy?
Every electrician has a favourite consumer unit to install, and each has advantages and disadvantages. Hager and MK are a good quality product and pleasant to install if you have a larger money. Lewden boards are a viable option if you need RCBOs but don’t want to spend as much money as you would on Hager.
How does a consumer unit work?
So just how does a consumer unit work? There are a number of components to consider – main switch, MCBs, RCDs, busbar and the incoming and outgoing cables. Let’s the journey of the electricity as it enters a dual RCD consumer unit. The description should give you a better idea of how to wire a consumer unit.
The mains cables (otherwise known as the consumer unit tails) coming into the consumer unit, usually have a cross-sectional area of 25mm2 and are cable of carrying up to 100A. These should enter via a consumer unit tails gland or sometimes it enters the consumer unit from the back of the board. The tails then feed into the top of the main switch.
If the mains switch is put in the OFF position then no power will be fed into the consumer unit.
On the bottom of the main switch are connected the interconnecting cables for feeding power to each of the RCD’s. Each RCD will have its own neutral terminal bar. It’s important the neutrals from one RCD are not mixed up with the neutrals from the other, otherwise we will get nuisance tripping of the RCD.
Once the current has fed through the RCD, the busbar (solid copper bar under the MCBs) carries the electricity into each of the circuit breakers (MCBs). If each individual MCB is in the ON position the current will flow through onto the final circuit attached on the top terminal of the MCB.
The current flows through the circuit, around the house to each socket, light etc.
Should a circuit exceed the current rating on the MCB then the MCB will trip off. Should there be a current imbalance greater than the stated current (typically 30mA) on any of the circuits covered by the RCD, then the RCD will trip off.
Frequently asked questions
Consumer units are often placed in hidden away locations which can be difficult access – which is not ideal. If a consumer unit is being changed, it is normally the case that it will be replaced in the same location. (It is possible to relocate a consumer unit, but it involves, among other things, lengthening (or shortening) each cable entering the consumer unit).
Where you are fitting a new consumer unit the regulations state it should be easily reachable and be mounted with the switches at a height of between 0.45m & 1.2m above floor level.
A consumer unit should ideally not be fitted in a bathroom, near a gas meter or in a location which is very humid or outdoors (unless the consumer unit has a suitable IP rating).
It is often the case that these locations may only require two circuits (normally a socket circuit and a lighting circuit). In that case, a 2 way garage unit (with or without an RCD) would suffice for this scenario.
If any of the switches in the consumer unit trip off the first thing to try is to switch them back on. Sometimes an RCD may trip off if an old style incandescent light bulb blows. The RCD can simply be switched back on; change the light bulb and away you go. However, if the tripped switch trips itself off again, ie it simply won’t stay in the on position then there is likely to be a fault on the circuit.
One thing to try, is to unplug all the appliances in the house connected to the problem circuit and then try to switch it on again. If it tips now, then you know it is an issue with the electrical installation. At this point it is best to call us for assistance
. If you require help in deciding whether to upgrade your consumer unit or have a new consumer unit installed in your property, then do give us a call and we’d be happy to provide you with a quote..
The condition of the earthing conductor and the earth bonding cables will be inspected on the site survey and if they are the wrong size or in a bad condition then they should be replaced. However, in many cases the earthing is suitable to reuse in the new consumer unit.
- The type of circuit overload protection will have longer disconnection times. What that means is, if there is too much current being drawn on a circuit (may be too many electric heaters are on one circuit) then the fuse wire will blow (or MCB trip off) in order to protect the cable from overheating and eventually melting.
- It is actually quite difficult and potentially dangerous to replace the fuse wire after it has blown. The fuse wire may ‘blow’ on a dark winters evening, causing the lighting circuit to switch off, just when you need to see what you are doing to replace the fuse wire. You then have to remove the cover on some fuse boards to get to the fuse, which means live parts are exposed. Then it can be quite fiddly undoing the screw and threading the fuse wire into the fuse holder, all while you are crouched on your knees in the under stairs cupboard in the dark! Not ideal.
- There is likely to be no RCD (Residual Current Device) protection on a fuse board – more on this later. This means you and your family are more susceptible to an electric shock in the event of an electrical fault. The fuse (or MCB) will protect the cable, however, the RCD will protect you should you touch a live part of the installation. In that event, you become a part of the electrical circuit and some current flows through you to earth. This creates an imbalance in the current which has flowed out from the supply compared to what has flowed back. The RCD picks up this imbalance and trips off.
Some old fuse boards may have an old fashioned earth leakage device sited before the fuseboard. However, these will not meet the higher modern standards and best replaced. They deteriorate over the years and don’t trip off in the required time.