Explaining: IP ratings

The IP Rating system is there to provide a guide to the degree of protection that lighting equipment has against the ingress of solids and liquids. The ratings are defined in international standard EN60529.

The First Number (IPn*) relates to solids and ranges from 0 – 6. 

The numbers offer a logical progression that indicate protection from the ingress of larger to smaller objects, so the lowest number (zero) indicates that there is no protection against touching live parts within the equipment.

The most common rating intended for general interior use is IP20, which tells you that nothing larger than 12.5mm diameter can reach a live part when the equipment is fully assembled.

A given rating is based on the complete assembly of a piece of equipment, as it would be used in an installation. It is important to understand this. Many fixtures use a protective cover to conceal the live parts. The IP rating only holds good with that cover in place. There are also luminaires where the IP rating only applies when the fixture is installed; the nature of the installation defines the IP rating (such as a downlight mounted into a ceiling).

The Second Number IP*n) relates to liquids and ranges from 0 – 9. 

Ratings for liquid ingress differ from that of solids. The second number relates to different styles of liquid ingress; drips, sprays, splashes, jets and immersion.  And it’s important to note that protection against one type of ingress does not assume protection against other types of liquid ingress. This is a common misunderstanding with IP liquid ratings.

This means that IP*5 is not necessarily more suitable than an IP*4 for a specific installation. Particular care needs to be taken with the higher ratings. Protection in particular circumstances cannot be assumed. The actual protection should be explained in the manufacturer’s documentation.

The installation conditions of immersible ratings must also be checked with care. An IP67 luminaire can be immersed up to a shallow depth of only 1000mm. But the manufacturer’s data may put a time limit on that immersion, so a ‘generic’ IP67 uplight to be fitted permanently in a garden pond may not be suitable. Always check the manufacturers data.

An IP68 rating also needs to be checked, because a similar situation may refer there. Unlikely as it seems, not all IP68 luminaires are designed for complete protection against water ingress. An IP68 rating can be given for a luminaire where water can enter but only in such a way that it does not present any danger.

What does the X mean in an IP rating?

Occasionally,  a number is replaced by an X (IP nX or IP Xn). This does not mean that the fixture has no protection against solid or liquid ingress. It means that no data is available to confirm a rating. It may be that a common-sense evaluation is assumed. If a fixture has a decent IP rating against ingress of liquids, then an assumption for ingress of solids can be made. Again, this is in the hands of the manufacturer and the specification should make reference to it. It doesn’t work the other way around. No assumption on liquid ingress can be made on the basis of a rating for ingress of solids.

Additional IP numbers

The most common Additional Number in the lighting industry is the one that covers Mechanical Impact Resistance. It’s most commonly seen in relation to exterior public area lighting where there is a higher likelihood of damage being done, leaving electrical connections dangerously exposed. This used to be known as the ‘third’ IP number but has been superceded by an IK number. There are 10 ratings available.

As a rule-of-thumb guide, many manufacturers have their outdoor equipment rated at IK08 and it’s useful to take that as a minimum specification rating.

There is no test for longevity

The IP tests take place in a laboratory environment, not in the ‘real world’. Some luminaire bodies will deteriorate in time, or due to environmental exposure (salt in the air, for example, or sunlight on plastics). Always talk to the manufacturer about specific installations – and get it in writing.

Typical IP numbers associated with lighting equipment

  • IP20: for most general purpose interior luminaires
  • IP44: common for street lighting and basic bollards and floodlights.
  • IP65: very common for outdoor lighting in public areas and for professional floodlighting
  • IP67: considered as a luminaire that can be immersed in water, but beware the time-limit caveat on this one.
  • IP68: an absolute requirement for underwater luminaires, but ONLY underwater.

The IP numbers themselves

Protection rating against ingress of solids (IPn…)

  • 0: No protection against contact and ingress of objects at all
  • 1: Protection against objects  >50mm, but no protection against deliberate contact with a body part
    2: Protection against objects >12.5mm, such as fingers or similar objects
  • 3: Protection against objects >2.5mm, typically tools and thick wire
  • 4: Protection against objects >1mm, which includes most wires and slender fixings (screws, etc)
  • 5: Protection again ‘dust’, though not entirely prevented, is not sufficient to interfere with satisfactory operation  of the equipment
  • 6: ‘Dust Tight’, meaning that there is NO ingress of dust and provides complete protection against contact with internal parts

Protection rating against ingress of liquid (IP…n)

  • 0: No protection against liquid ingress
  • 1: Protection against vertically falling dripping water.
        Duration: 10 minutes (water equivalent to 1mm of rainfall per minute)
  • 2: Protection against dripping water when the equipment is tilted at 15deg. from its normal position.
        Duration: 10 minutes (water equivalent to 3mm of rainfall per minute)
  • 3: Protection against a spray of water at any angle up to 60deg. from the vertical.
        Duration: 5 minutes. Water volume: 0.7L/min. Pressure: 50-150kPa
  • 4: Protection against water splashing against the equipment from any direction.
        Duration: 5 minutes. Water volume: 10L/min. Pressure: 50-150kPa
  • 5: Protection against water projected from a nozzle from any direction. 
      Duration: (at least) 3 minutes. Water volume: 12.5L/min. Pressure: 30kPa at 3m.
  • 6: Protection against a powerful jet of water from a 12.5mm nozzle from any direction.
        Duration: (at least) 3 minutes. Water volume: 100L/min. Pressure: 100kPa at 3m.
  • 7: Protection against a harmful quantity of water when the equipment is immersed, under defined conditions of pressure and time.
        Duration: 30 minutes. With the lowest point of the equipment 1000mm below the surface of the water, or the highest point being 150mm below the surface, whichever is deeper. 
  • 8: Protection against continuous immersion in water beyond a depth of 1m, under conditions specified by the manufacturer.
        Duration: continuous. Depth specified by the manufacturer, generally up to 3m

The IK numbers relating to mechanical impact resilience

  • 00: Unprotected, or where no test has been carried out.
  • 01: Impact energy of 0.15J (Joules), equivalent to dropping a 200g object from a height of 75mm onto the equipment.
  • 02: Impact energy of 0.2J, equivalent to a 200g object dropped from a height of 100mm. 
  • 03: Impact energy of 0.35J, equivalent to a 200g object dropped from a height of 175mm.
  • 04: Impact energy of 0.5J, equivalent to a 200g object dropped from a height of 250mm.
  • 05: Impact energy of 0.7J, equivalent to a 200g object dropped from a height of 3350mm.
  • 06: Impact energy of 1J, equivalent to a 500g object dropped from a height of 200mm.
  • 07: Impact energy of 2J, equivalent to a 500g object dropped from a height of 400mm.
  • 08: Impact energy of 5J, equivalent to a 1.7kg object dropped from a height of 200mm.
  • 09: Impact energy of 10J, equivalent to a 5kg object dropped from a height of 200mm.

IP ratings are there as a guide to safety. Taking advice from manufacturers is always recommended. If an equipment supplier can’t provide the advice that’s being sought, it may be best to reconsider the specification.

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John Bullock is the editor of The Light Review

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