Choosing a suitable RCCB for Special Locations

(16/04/2009)

The new 17th Edition of the IEE Wiring Regulations gives particular attention to protection in so-called Special Locations. These include, for example, swimming pools, marinas and other basins, as well as caravan and camping parks. In general, the requirements for these areas dictate the almost universal provision of residual current protection, typically in the form of an RCCB (residual current circuit breaker).

Choosing a suitable RCCB is, however, not always as easy as it may seem. Let’s first consider caravan and camping sites. These days, it’s very likely that a high proportion of the loads will be electronic – televisions, computers and even fluorescent lights with high-frequency ballasts fall into this category. Loads of this type generate pulsed DC residual currents that can prevent standard RCCBs from tripping under fault conditions.

Not surprisingly, leading manufacturers of RCCBs such as Schneider Electric have developed products to overcome this difficulty, and in many cases, so-called Type A devices will provide a satisfactory solution. However, where there is a very high proportion of electronic ballast loads, or where the loads include a lot of equipment fitted with interference filters, a better choice is likely to be the new reference Si RCCBs.

These also have the benefit of reduced sensitivity to the supply surges caused by lightning strikes, which may be an important benefit on those camping and caravan sites that are fed by long outdoor overhead lines.

But what of swimming pools and similar installations? In some cases, these may pose problems that are somewhat similar to those already discussed, in that the loads could include fluorescent lighting, and any pumps used may, in these energy conscious days, be fitted with variable speed drives. In these instances, the use of a Type A or reference Si RCCBs is recommended.

There is, however, another issue to be considered – that of the potentially corrosive environments. The presence of moisture, possibly loaded with salt, is a distinct possibility, and chlorine, which combines with water to produce hydrochloric acid, is commonly used to treat the water in swimming pools. RCCB devices used in these areas are typically enclosed in protective enclosures. This adds to cost, however, and even the best of enclosures offers no useful protection when the door is open.

There is another solution – RCCBs that can withstand adverse operating conditions. Once again, Schneider Electric can offer suitable products, in the form of reference SiE RCCBs, which are specially sealed to prevent the ingress of moisture and other contaminants. These devices have exactly the same electrical characteristics as reference Si RCCBs, and so provide excellent protection with a minimum risk of nuisance trips in even the most demanding of applications.

While most electrical contractors as well as the specifiers and designers of electrical installations now understand that the 17th Edition of the IEE Wiring Regulations places greatly increased emphasis on the use of residual current protection, not all may yet be aware of the benefits offered by Type A, reference Si and reference SiE devices, particularly in Special Locations.

The criteria for selecting these products are, however, reasonably straightforward, as has been outlined in this brief item. And further advice is, of course, readily available from expert suppliers of circuit protection equipment such as Schneider Electric.

Related categories:  Circuit breakers MCB, MCCB, ACB