Guide to IP ratings

An IP rating tells you how well an electrical enclosure protects its contents against solid objects, dust and water. IP stands for International Protection, although it’s more commonly referred to as Ingress Protection. The rating system is defined by EN 60529 and provides a standard way of comparing the protection offered by different enclosures.

How to read an IP rating

An IP rating normally consists of the letters IP followed by two numbers, for example IP56:

Digit	Meaning
5 — first digit	Protection against contact with dangerous parts and the ingress of solid objects or dust
6 — second digit	Protection against harmful ingress of water

The letter X can be used instead of either number when that particular type of protection isn’t applicable or isn’t required. IP4X, for example, specifies protection against solid objects greater than 1mm without specifying a water-protection requirement.

First digit: protection against solids and dust

Rating	Level of protection
IP0X	No specified protection against contact or solid foreign bodies
IP1X	Protection against large-area contact and solid objects greater than 50mm
IP2X	Protection against finger contact and solid objects greater than 12mm
IP3X	Protection against tools, wires and solid objects greater than 2.5mm
IP4X	Protection against tools, wires and solid objects greater than 1mm
IP5X	Dust protected — some dust may enter, but not enough to interfere with satisfactory operation
IP6X	Dust tight — no penetration of dust

Second digit: protection against water

Rating	Level of protection
IPX0	No specified water protection
IPX1	Protection against vertically falling water drops
IPX2	Protection against dripping water when tilted up to 15°
IPX3	Protection against spraying water up to 60° from vertical
IPX4	Protection against splashing water from all directions
IPX5	Protection against water jets
IPX6	Protection against powerful, heavy water jets
IPX7	Protection against temporary immersion in water
IPX8	Protection against the effects of long-term, continuous immersion
IPX9	Protection against high-pressure, high-temperature water jets

Choosing the right IP rating

It can be tempting to simply specify the highest IP rating available, but a higher rating isn’t necessarily more appropriate for every installation. Over-specification can increase cost and may make an enclosure less suitable for applications where ventilation, pressure compensation or drainage matters. Where equipment generates significant heat, for example, ventilation may be needed to keep it within its designed operating conditions — and any opening designed for ventilation or drainage needs care, since it can affect the enclosure’s IP rating.

When specifying an enclosure, work through:

• Dust and solid objects — what particles or foreign objects could reach the enclosure?
• Water exposure — will it encounter dripping water, splashes, jets or immersion?
• Heat and condensation — could temperature and humidity changes cause condensation inside it?
• Cable entries — how many cables need to enter, and how will those entry points be sealed?
• Maintenance — will the enclosure need opening regularly for inspection or alteration?
• The wider environment — could it be exposed to chemicals, salt water, acids, corrosion or UV?

IP rating doesn’t mean corrosion resistance

IP ratings relate specifically to ingress protection. The tests behind them are comparative and use fresh water, so an IP rating alone doesn’t indicate how well an enclosure withstands salt water, chemicals, acid rain, corrosion, UV exposure or other hostile environments — material selection needs to be considered separately. Moulded materials can offer good corrosion and chemical resistance, but performance varies by material and environment.

How is a high IP rating achieved?

Two enclosures with the same IP rating may achieve their protection in very different ways. Design choices — lid seals and gaskets, screw-fixed lids, push-click closures, gel filling, knockouts and specially designed cable entries — all affect purchase price, installation time, reliability, maintenance requirements and longevity.

The gap between an enclosure body and its lid is an obvious potential route for dust and moisture, which is why seals are commonly used at this interface. Integrated seals have an advantage here, since a separate gasket can move, fold or become displaced during installation.

For applications requiring IP68 protection, an enclosure can also be filled with silicone gel after the electrical connections have been made. This isolates the components from the external environment, but accessing the connections later means disturbing the gel and replacing it — better suited to installations meant to remain undisturbed than ones needing frequent maintenance.

Don’t compromise the rating during installation

Selecting the right enclosure is only the first step — poor installation practice can compromise its designed-in protection. Common mistakes to avoid:

• Positioning cable entries on top of an outdoor enclosure, where water can collect around the entry seal.
• Screwing labels or signs through the enclosure lid, which creates an additional ingress path.
• Ignoring condensation — high humidity combined with significant temperature swings may need ventilation or breather arrangements.
• Fixing through the rear of the enclosure incorrectly — mounting holes can compromise the rating unless the right sealing or external mounting system is used.
• Displacing a gasket when closing the lid — a loose or folded gasket can stop the enclosure sealing correctly.

Quick IP rating checklist

Before selecting an enclosure, ask:

1. What level of protection against solids and dust is required?
2. What type of water exposure will the enclosure experience?
3. Is temporary or continuous immersion possible?
4. Are condensation or major temperature changes likely?
5. Does the enclosure material suit the chemical, corrosive and UV environment?
6. Where will cables enter the enclosure?
7. How will the enclosure be mounted?
8. Will regular access or maintenance be required?

Choosing the correct IP rating means considering the whole application rather than simply picking the highest number. The enclosure, material, cable entries, mounting arrangement, ventilation and installation method all contribute to the finished solution.