The easy way to selection
By Simon Rowlinson, Marketing Manager for Wylex
With the recent changes to the 17th Edition, the specification of consumer units has become something of a mystery to many but in order to try to help wholesalers understand and recommend the right consumer unit to their customers for a new 17th edition project, Wylex has come up with a simple way to simplify the specification of their units; in fact, it works rather well for consumer units in general.
The logic goes something like this; everyone understands the star rating system for hotels, the classification system that makes it easy to tell at a glance the difference between what a 2 star and 5 star hotel offers. So Wylex thought why not take this idea and apply a consumer unit rating using those familiar 5 stars to show what you get from a specific model. At the same time, it actually gives a rough guide to seeing ultimate value for money, performance and safety.
Keep it simple
All types of Wylex consumer units can be installed under the 17th edition; it’s the application of the circuit protection design that dictates how they comply and the resulting levels of protection offered. So, where a 2 star hotel is a basic minimum, the minimum standard for a consumer unit says it will comply to the 17th simply by having been fitted with a couple of 30mA RCDs. But there are times when your customers may require a lot more.
So what is the Wylex 5 Star Rating? Let’s start by looking at the 17th edition.
These are summaries of the new regulations that apply:
1. Cables concealed less than 50mm deep in a wall/partition that are not mechanically protected by an earthed metallic covering must be 30mA RCD protected (522.6.6, 522.6.7, 522.6.8.)
2. Every installation must be divided into separate circuits to avoid hazards and minimise inconvenience in the event of a fault, and must take account of the danger that may rise from the failure of a single circuit such as lighting. The possibility of unwanted tripping of RCDs must be reduced (314.1).
3. For parts of the installation that require separately controlled circuits, these must not be affected by the failure of other circuits (314.2).
4. Socket outlets for general use by ordinary persons must be 30mA RCD protected (411.3.3).
5. All circuits in a room that contains a bath or shower must be 30mA RCD protected (701.411.3.3)
It is worth noting that 30mA protection may be offered by any mechanical switching device or association of devices such as a RCBO, RCD or any other equipment designed to open contacts when the residual current attains a given value.
It’s quite easy to meet three of the summary points 1, 4 and 5 with basic 30mA protective devices in order to comply with each regulation in isolation. But in practice, these must be combined with the other summary points 2 and 3; it’s now you need to apply some electrician’s knowledge based on understanding the final installation, to choose the right type of consumer unit, and then come up with the best solution.
So, what types of consumers units are there?
Four generic consumer unit types are considered here: Main Switch, Split Load, High Integrity and Dual RCD. They differ in the way that they provide 30mA earth fault protection, particularly on independent circuits.
When fitted with independent RCBOs, a unit with a Main Switch incomer complies completely with all five summary points, because this arrangement assures continuity of supply better than any other arrangement; if one device trips due to an earth fault, none of the others are affected
Where any independent circuits are required as in paragraph 3, Dual RCD units can never comply.
But that’s not to say that 30mA RCD group protection can’t be used. Circuits that are protected by a combination of MCBs and a RCD benefit from two-pole protection under earth fault conditions. High Integrity and Split Load units can both comply with paragraph 3 because they both can accommodate circuits that require independent protection i.e. a 30mA RCBO can be fitted where required.
A simple guide
Wholesalers can now easily help to guide the contractor and offer them the best and safest solution for today and for the future. Wouldn’t you agree that the more independent RCBO protected circuits that are used or maybe added to a consumer unit, the more an installation complies? The ‘minimum end user’s expectation’ will be set by the consumer unit your customers decide to install to set the overall star rating of the installation, which in turn sets the rating their customers will ultimately give them.
With the Solution 17 star rating system from Wylex, the most appropriate consumer unit and devices for each individual installation, from a basic minimum standard through to 5 star rating, can now be selected.
Finally, like simply choosing a hotel room today, the Wylex Solution 17 star rating system will help everyone involved to choose and to specify the most economically and electrically appropriate solution every time.
A wall chart is also available from Wylex to remind you and your customers which consumer units are available, and their specifications.