IP Protection Rating Explained: How to Read an IP Code
IP protection rating: What the digits of an IP code mean, the difference between IP31 and IP65 and how to choose the right rating for a switchboard.
ContentsAn IP protection rating is a two digit code describing how well an enclosure resists the ingress of solid objects and water. It is standardised in IEC 60529 and it is the most frequently specified, and most frequently misunderstood, figure in switchboard documents. The code says nothing about mechanical strength, corrosion resistance or thermal performance; it only defines what can get inside.
How to read an IP code
The code consists of two digits after the letters IP. The first digit describes protection against solid objects and dust, the second describes protection against water. IP54 therefore denotes an enclosure where a limited amount of dust may enter without impairing operation, and which withstands splashing water from any direction. When a digit is replaced by X, that criterion has simply not been tested; IPX4 means only the water test was performed.
What each digit means
| Digit | First digit: solid objects and dust | Second digit: water |
|---|---|---|
| 0 | Unprotected | Unprotected |
| 1 | Solid objects 50 mm and larger (back of hand) | Vertically dripping water |
| 2 | Solid objects 12.5 mm and larger (finger) | Dripping water tilted up to 15° |
| 3 | Solid objects 2.5 mm and larger (tools, wires) | Spraying water up to 60° |
| 4 | Solid objects 1 mm and larger (thin wire) | Splashing water from any direction |
| 5 | Dust protected (limited ingress) | Low pressure water jets from any direction |
| 6 | Dust tight | Powerful water jets |
| 7 | — | Immersion at 1 m for 30 minutes |
| 8 | — | Continuous immersion at a pressure defined by the maker |
| 9 | — | High pressure, high temperature water jets |
Choosing a rating for a switchboard
- IP31 to IP41: clean, dry, air conditioned electrical rooms; gives the best thermal performance
- IP54: industrial production areas, dusty environments, spaces not subject to wash down; the most common choice
- IP55: food and beverage plants cleaned with pressurised water
- IP65 to IP66: outdoor sites, field enclosures, wash down lines, cement and mining sites
- IP67 and above: special applications with a risk of submersion; rarely required for a switchboard
A higher IP is not always better
As the IP rating rises the enclosure becomes sealed and natural ventilation disappears. That makes it harder to reject the power lost inside the board; the same equipment layout reaches a noticeably higher internal temperature in an IP65 enclosure than in an IP31 one. The consequences are larger busbar and cable cross-sections, or closed loop cooling such as heat exchangers and air conditioners. IP selection therefore belongs with the thermal calculation, an approach we cover in our article on busbar capacity and derating.
The second issue is sealing hardware. The performance of an IP55 or higher enclosure depends on door gasket quality, cable gland selection and the sealing of every hole cut during installation. A single irregular hole drilled on site in a gland plate effectively invalidates the rating of a certified enclosure.
Key takeaways: IP protection rating
- How to read an IP code — The code consists of two digits after the letters IP.
- A higher IP is not always better — As the IP rating rises the enclosure becomes sealed and natural ventilation disappears.
- Standard source — IEC publication catalogue: iec.ch.
Frequently asked questions
What is the difference between IP54 and IP65?
IP54 allows limited dust ingress and withstands splashing water, while IP65 is dust tight and withstands low pressure water jets. The difference is not only sealing: because heat rejection falls in an IP65 enclosure, a cooling solution usually becomes mandatory.
Does the IP rating cover impact resistance?
No. Mechanical impact resistance is defined separately by the IK code. An enclosure can be IP66 and still have a low IK value, so outdoors both should be specified together.
Related articles
- IK Impact Rating Explained: IK07, IK08 and IK10 Compared
- Switchboard Technical File, Rating Label and CE Conformity
- Short Circuit Withstand in Switchboards: Icw, Ipk and Conditional Rating
- All technical articles
At Devpan we set the IP rating together with site conditions, the cleaning regime and the thermal load calculation, and we detail gaskets, glands and cable entries to suit the chosen class. Share your ambient conditions and you can see the hidden cooling cost of an unnecessarily high IP rating in advance.
