Replacing a fuse box
There are two main types of fuse board change (consumer unit):
For clarity the correct terminology for a fuse board, fuse box, motherboard, main fuse and the many other terms we’ve heard is a consumer unit.
Dual RCD Consumer unit
A Dual RCD consumer unit is a consumer unit with two RCD’s. RCD stands for residual current device.
An RCD is designed to protect the user by disconnecting the electrics quickly enough to prevent death. Typically a consumer unit of dual RCD design will be laid out with the following circuits (found in a typical 3 bedroom home):
- RCD 1: Ground floor lights, 1st floor sockets, Kitchen sockets, Smoke Alarms
- RCD 2: 1st floor lights , ground floor sockets, Cooker, Immersion Heater/Boiler
Each of these circuits will be protected by individual MCB’s (Miniature circuit breakers or flick switches as people like to call them). These protect against over current preventing the circuit from drawing more current then it was designed for.
The disadvantage to this design is that, for example, if a light bulb blows on the ground floor this will trip RCD 1 (trip refers to switch off or disconnect). This will in turn switch off not only the ground floor lights but also 1st floor sockets, kitchen sockets and smoke alarms. So say you were on your computer, which is plugged into your 1st floor sockets and you’re writing an important e-mail, then a bulb on the ground floor blows. This would result in you losing your e-mail as RCD 1, which protects them both, would trip.
The advantage of this consumer unit layout is that it’s inexpensive which normally suits landlords, those who don’t intend to live in their current home for too long or those who are on a tight budget.
Consumer unit with RCBO’s
A consumer unit with RCBO’s is a consumer unit which consists of an RCBO for each circuit. RCBO stands for residual current circuit breaker with overload protection. An RCBO like an RCD protects the user by disconnecting the circuit quickly enough to prevent death and also has overload/over current protection built in.
As each circuit has its own RCBO, if a light bulb blows on the ground floor it only trips the ground floor lighting circuit and therefore this minimises any inconvenience.
The only disadvantage is the cost, as RCBO’s are expensive to purchase.
So how do I know what size consumer unit to order?
In order to work out what size consumer to order, you need to look at your existing fuse box.
The number of fuses = the number of circuits.
Therefore if you count 8 fuses you will need to order either a Dual RCD consumer unit suitable for 10 Circuits OR a consumer unit with 10 RCBO’s, depending on which type of consumer unit you have decided on – 10 because we should always leave 1 or 2 spare circuits.
This picture of a typical consumer unit, as shown above there are 8 fuses numbered therefore you have 8 circuits. Each fuse has the current rating written on it, the colour also signifies the rating.
Red = 30A, Blue = 15A, White = 5A. In this example you would have 4 x 5A, 1 x 15A and 3 x 30A.
Is there anything I need to know before I have a new fuse board (consumer unit) fitted?
Yes, we or someone else needs to verify that the installation is safe to alter. This is done by carrying out an electrical installation condition report. An engineer needs to come and test the wiring end to end and carry out various checks including visual, test and measurement. The installation needs to satisfy certain requirements before a new consumer unit is fitted. One of the most important is earthing and bonding:
The process of a fuse board change at C J Sparks Ltd
- You contact us to place your order. If your unsure of any details regarding your existing fuse box you can send us some photos, we can identify what we need to from these.
- Our engineer will arrive at 8am (our standard start time) on the agreed date and introduce him or herself. They will arrive wearing overshoes to ensure they do not get your floors dirty.
- Our engineer will then need to switch off your electricity to begin the fuse box change process. The electricity in most cases will be off until 3-4pm
- Once the fuse box change has been completed the engineer will begin to carry out electrical testing. This will involve testing the wiring end to end ensuring that the electrical installation is safe.
- The engineer will then tidy up ensuring the same standard of cleanliness as when they arrived
- Upon completion of this the engineer will talk you through how the consumer unit functions and also about the safety of your current electrical installation. We will then send you the completion certificate and building regulations notification with the local council notified following payment.
Note, should an electrical installation condition report not be previously carried out, this will be required before a fuse board change is to take place. This is to ensure that we the installation is safe to alter.
Summary of the consumer unit installation
- New consumer unit with modern safety devices fitted by a qualified professional.
- Upgrade of main supply tails and main earth if required (consumer unit must be within 2 meters of the electric meter).
- Completion certificate provided and building regulations notification made.
Dual RCD consumer units with MCB’s
Up to 5 circuits allowing for 1 spare (6 total) £350 excluding VAT (£420 including VAT) supply and fitting
Upto 9 circuits allowing for 1 spare (10 total) £400 excluding VAT (£480 including VAT) supply and fitting
Upto 17 circuits allowing for 1 spare (18 total) £600 excluding VAT (£720 including VAT) supply and fitting
Consumer units for RCBOs
Upto 9 circuits allowing for 1 spare (10 total)£280 excluding VAT (£336 including VAT) supply and fitting for the board only
Upto 19 circuits allowing for 1 spare (20 total)£500 excluding VAT (£600 including VAT) supply and fitting for the board only
£80 excluding VAT (£96 including VAT) per RCBO needed
BS7671:2008 Amendment 3 2015
Any consumer unit that we fit within a domestic premises will be compliant with the latest regulations; basically, the consumer unit will be made from a non combustible material.
What about an electrical installation condition report?
Carrying out an electrical installation condition report requires an excellent knowledge of not only correct electrical regulations but also, past ones too.
We charge £150 (£180 inc VAT) for the first 4 circuits or part of and then £25.00 (£30 inc VAT) per circuit thereafter.
But do I really need to change my consumer unit?
Not necessarily. It really depends on several factors but we would always recommend an electrical installation condition report be carried out to decide this.
- The factors that could affect whether or not you need to change the fuse board are:Having or planning to have new electrical work e.g. new sockets installed and you don’t currently have RCD protection for the circuit that covers those electrics
- You would like the new safety features that come with a modern fuse board/consumer unit
- You worry about have to change fuse wire or a fuse in the event of it blowing
- If you live in a flat above the ground floor, aren’t planning to have any new electrics completed, then you probably won’t need to change your consumer unit as RCD protection won’t necessarily be required but we still recommend an electrical installation condition report be carried out
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