Ingress protection techniques explained

One of the most critical factors in deciding which electrical enclosure or junction box should protect your electrical systems and their connections is its IP rating. No matter where the housing will be located, it needs to withstand whatever its environment throws at it. But how many people actually know how these IP ratings are achieved — and the ways they can be compromised during installation?

Chris Lloyd, Managing Director of Spelsberg UK, explains how different IP ratings can be reached and how to maximise an enclosure’s integrity.

The same rating, achieved differently

IP ratings relate to the degree of protection a housing offers against ingress from foreign bodies and moisture. EN 60529 outlines the universal rating system, which uses the letters IP followed by two digits: the first indicates protection against foreign bodies, the second protection from moisture (a third digit may indicate protection from mechanical impact, though it’s rarely used). As the numbers get higher, so does the level of protection — IP68 is the highest, offering total protection from fine dust and from complete, continuous submersion in water.

While the rating system itself is simple, the methods manufacturers use to deliver that protection are the product of years of research and development. Two enclosures with the same overall rating may achieve it in very different ways, which can have a big impact on purchase cost, installation time and the longevity of the product. Understanding the different techniques is the first step in making the right choice for a given application at the specification stage.

Sealing the lid

The most obvious way for debris or moisture to enter an enclosure is through the gap between the body and its lid. No matter how precisely an enclosure is manufactured, microscopic particles of dust and water droplets will find their way through any gap left unsealed. This is why higher-quality enclosures feature sealing arrangements around the lid.

Separate gasket seals have a habit of wandering out of position or folding during installation — infuriating, and dangerous, especially on site. To guarantee seals won’t fail, some manufacturers injection-mould the seal as a single construction that’s an integrated part of the enclosure rather than a separate component.

Enclosures designed for higher IP ratings typically need tooling to fix the lid in place. Often that’s as simple as a few small screws, but it plays an important part in pressing the seal securely flush against the surface so small impacts don’t disturb it. Medium and low IP ratings are more often supported with a push-click mechanism, which is quicker to use but allows a small degree of movement once closed. Hinges and other accessories can affect IP performance too — they may improve access, but they also introduce more gaps through which foreign bodies or moisture could get in.

Gel-filled enclosures

A popular technique for reaching IP68 is to fill the enclosure with a silicone gel after the connections have been made. This isolates the electrics from the external atmosphere entirely, so any moisture or dust that does get past the enclosure’s protection still won’t reach them. Gel-filled enclosures have distinct advantages and disadvantages that suit them to specific applications.

Using gel means an IP68 rating is easier to achieve and doesn’t need such expensive tooling, so the units are often cheaper to supply despite including the silicone mixing packs. Because internal protection is guaranteed by the gel, there’s also little need for a time-consuming, screw-down lid, which can speed up installation on jobs with numerous units.

The trade-off is that it’s impossible to access the connections without breaking the gel apart once it has set. In applications needing regular updates or routine maintenance, that becomes time-consuming and expensive, since a new gel pack is required every time. For a one-off installation left in an environment that demands IP68 protection — underground connections for external lighting, for example — gel-filled enclosures are the ideal solution. For most other applications requiring high IP, it’s generally better to pay a slightly increased premium for a product that achieves its protection through design and manufacturing quality instead.

Cable entries and knockouts

A final consideration at the specification stage is the number of entries required and how they’re presented. Many enclosures come with knockout points around the walls that are removed using the correct tools. This is preferable to pre-cut holes, since the enclosure is supplied with its IP rating intact. There’s a fine balance, though, between knockouts that are too hard to remove and ones that are too easy — either vastly increases installation time or risks accidental removal once in use.

Some manufacturers offer a customisation service that lets the customer specify the number, size and location of each entry point, so the product arrives ready to install with no unnecessary entry points opened. Where this is carried out on in-house CNC machines, it’s typically available without minimum order quantities, and a supplier’s sales team can help design the enclosure to the exact requirements of the application.

Sealing the entry itself

Specifying the correct enclosure is only the first step. As soon as a cable enters the unit, its IP rating is compromised, which makes specifying the correct entry sealing solution just as important. For high IP ratings, a traditional dome-topped cable gland offers the most secure seal, while push-fit membranes offer a faster solution for applications less exposed to the elements.

Classic installation mistakes to avoid

Even a correctly specified enclosure can lose its rating through a simple installation oversight. The most common mistakes:

• Positioning entry points on the top of an enclosure sited outdoors, where puddles collect around the seal and get drawn in by heat expansion and contraction.
• Fixing caution notices or signs to the lid with screws that perforate the enclosure.
• Not fitting breather valves in high-humidity environments with a large temperature differential.
• Compromising the enclosure by fixing it to a wall or bulkhead through the back panel — rather than using grommets over internal screw heads, or bracketing and DIN rail mounting that stays external to the internal box space.
• Using enclosures with loose gaskets that fall out of place as the lid is closed or tightened.

These are easy to avoid, and a good supplier should be able to advise on how to get the full benefit of an enclosure’s IP potential.

In short

Manufacturers invest heavily in developing techniques and product designs that maximise protection from moisture and foreign particles — some more reliably, some more quickly to install, than others. It’s always worth asking how an enclosure’s IP rating is actually achieved. A good supplier should be able to show you the options and help with specification.