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Hammond’s handy reference guide to IP ratings

07 September 2021

Environmental sealing is often required for small electronic systems installed in the factory environment. The white paper will help you select the appropriate IP rating.

Small electronic systems are increasingly being installed in the factory environment as part of distributed control and monitoring equipment. When it comes to the level of environmental sealing required from the enclosure, it is, as always, a balancing act. Over-specify for the application and the enclosure cost will be too high; under-specify and there is the risk of equipment failure or malfunction as the result of contaminant ingress. 

A few basic questions

Where will the product be used? Inside, outside or possibly both? For outside installation, UV stability is a potential issue for plastic enclosures, so polycarbonate is the default choice. For mobile applications such as road and rail, is shock and vibration likely to be a concern? Is the ingress of dust and water a possible issue? Are there likely to be contaminants such as oils and chemicals? If so, metal enclosures, particularly stainless-steel ones, typically offer better resistance than plastic ones. Is resistance to impact damage a possible problem? Are particularly high or low temperature expected?

Environmental sealing

The relevant international standard is IEC 60529. Typically, enclosures rated at IP54 are suitable for general purpose use; for installation in environments where dust and water are likely to be present, IP66, 67 or 68 would normally be specified. The highest rating is IP69K, which gives protection against steam cleaning at high pressure. In North America, enclosures' environmental sealing is normally defined as a NEMA (National Electrical Manufacturers Association) number. NEMA ratings also require additional product features and tests (such as functionality under icing conditions, enclosures for hazardous areas, knock-outs for cable connections and others) not addressed by IP ratings.

EN 60529 defines ratings as IPxx, where the first digit defines the protection against solid objects and the second the protection against water ingress. 

Protection classesfor solid object protection

First figure

Scope of protection


No protection.


Protection from solid objects greater than 50mm in diameter.


Protection against solid objects greater in diameter than 12.5mm.


Protection against solid objects greater in diameter than 2.5mm.


Protection against solid objects larger than 1.0mm.


Protection against the ingress of dust in harmful quantities.


Dust tight.

Protection classesfor water protection

Second figure

Scope of protection


No protection


Protected against vertically falling drops of water.


Protection against falling water droplets up to 15° from the vertical.


Protected against direct water sprays from up to 60 degrees from the vertical.


Protected against splashing water from any direction.


Protection against low pressure 6.3mm jets of water sprayed from any angle.


Protection against powerful 12.5mm water jets from any angle.


Protection against temporary immersion in water up to 1 metre deep.


Protection against continuous immersion in water greater than 1 metre in depth.


Protection against high-pressure, high-temperature jet sprays, wash-downs or steam-cleaning procedures.

As an example, IP68: the first digit "6" means totally dust tight and the second digit "8" means protection against continuous immersion in water greater than 1 metre in depth.

Many of our plastic, die-cast and metal enclosures offer third-party tested high IP ratings. Our digital shortform Industrial Enclosures catalogue is an easy-to-use overview of our main IP rated ranges.

The catalogue gives full technical details and part numbers for each product, and 'Quick Links' go to the relevant page on the Hammond website, from where detailed CAD drawings can be downloaded so that configuring the enclosure to the application is much simplified. Hammond is, of course, very happy to supply you with a configured version of the standard product. 

The selected families in the catalogue are:

• 1554 IP68 polycarbonate with flat lid. 
• 1555 IP68 polycarbonate with styled lid.
• 1554PB IP66 polycarbonate pushbutton.
• 1555F IP68 polycarbonate flanged lid enclosures.
• PCJ IP66 polycarbonate junction box with latching lockable cover.
• 1590Z IP65 GRP heavy duty enclosures.
• PJU IP66 GRP junction box with hinged cover.
• EJSS IP66 304 stainless steel junction box with continuous hinged cover.
• 1590 IP68 die-cast aluminium rugged enclosure.
• Accessories: IP68 brass and nylon cord grips; IP66 stainless steel and non-metallic IP66 hole plugs; rainproof ventilators

Our general digital shortform gives details of all our major enclosure product ranges.

A digital version of our current English language shortform catalogue can be downloaded as a 4MB PDF. If you would like us to send you a printed copy, please email

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