The different types of domestic consumption units
Main switch consumer units
The simplest form of consumer unit, the main breaker board is supplied with only a 100A mains isolator. When the 17th Edition of the Regulations came into force, it seemed to many that the days of the mains breaker main, supplied without RCD, were numbered.
However, main breaker fuse boards, when used in conjunction with a full bank of RCBOs, are now considered the best way to satisfy 17th Edition as this allows complete separation of circuits and prevents nuisance tripping. .
The downside to this installation is cost, as using individual RCBOs is considerably more expensive than using RCDs with MCBs. However, many homeowners are willing to pay the extra cost for the peace of mind that RCBOs provide.
High integrity boards
A ‘High Integrity Consumer Unit’ is one that allows superior circuit separation while protecting all circuits from ground leakage. It does this by using three neutral bars that allow the use of 2 RCDs and a full bank of RCBOs.
Therefore, the user can protect all non-mission critical circuits, such as lighting and main ring on RCDs, while protecting all mission critical circuits independently with RCBOs. In this situation, a problem with the refrigerator will not affect the smoke alarms or, for example, the alarm system will not cut off power to the tropical fish tank. High integrity panelboards provide very good compliance with the 17th Edition Wiring Regulations.
Split Load Consumer Units
A split load switchgear, in common parlance, is one that is supplied with a main switch and RCD. Now that we are operating under the 17th edition regulations, the implied charge of a split charging unit is that MCBs should only be placed on the RCD side while RCBOs are installed on the main breaker side.
A split load switchgear, used in this way, meets the 17th Edition Regulations particularly well and cost-effectively as it protects all circuits from ground faults and reduces the risk of nuisance tripping on mission critical circuits through good circuit separation.
Garage consumer units
The term ‘garage consumer unit’ applies to smaller consumer units and there is nothing more special about these consumer units. Most normal home environments have only a small number of circuits in their garages, garden sheds, and outhouses, and therefore do not require the larger 10-way to 36-way fuse boards used in the main home.
Garage units typically have between 2 and 5 shapes, depending on what is used in the toilet. A normal shed with lighting and a couple of plugs would use a 2-way unit, while a shop using a lathe and power tools might go for a 5-way unit.
Fully loaded consumer units
These consumer units usually come with 2 RCDs and a full bank of MCBs and usually have between 10 and 15 usable ways. While they are very cost effective and fully 17th Edition compliant, they do not provide very good circuit separation.