The IP Rating Often Includes a Third Digit Denoting Impact Resistance
The ability of an enclosure to protect a piece of equipment from outside elements (such as rain, or to keep fingers away from electrical circuits) is called "environmental protection" and is often specified by "IP" ratings (standing for "ingress protection"), which are specified by European Standard IEC 60529.
Naturally, higher degrees of protection can increase the cost of a product, and should be applied only when necessary to ensure safe and functional operation of the product in the environmental conditions and application in which it will be used. Please refer to the appropriate sections of IEC 60529 for complete information on the standard. The following is a brief summary of the IP rating system.
The first digit of the IP designation describes the degree of protection against access to hazardous parts.
The second digit designates the degree of protection against water.
The third digit describes the degree of protection against mechanical impact, and is often not specified.
1st / Protection against foreign objects / 2nd / Protection against water / 3rd / Protection against mechanical impacts
0 / Not protected / 0 / Not protected / 0 / Not protected
1 / Protected against objects greater than 50 mm diameter / 1 / Protected against dripping water / 1 / Impact 0.225 joule
2 / Protected against objects greater than 12 mm diameter / 2 / Protected against dripping water when tilted up to 15 degrees / 2 / Impact 0.375 joule
3 / Protected against objects greater than 2.5 mm diameter / 3 / Protected against spraying water / 3 / Impact 0.60 joule
4 / Protected against objects greater than 1.0 mm diameter / 4 / Protected against splashing water / n/a / -----
5 / Dust protected / 5 / Protected against water jets / 5 / Impact 2.00 joule
6 / Dust tight / 6 / Protected against heavy seas / n/a / -----
n/a / ----- / 7 / Protection against the effects of immersion / 7 / Impact 6.00 joule
n/a / ----- / 8 / Protection against submersion / n/a / -----
n/a / ----- / n/a / ----- / 9 / Impact 20.00 joule
Example:A rating of IP-21 indicates that the enclosure offers protection from objects greater than 12-mm in diameter, such as a typical person's finger or a metal rod (indicated by the first digit being "2"), and protection from water dripping onto the unit without the unit becoming electrically unstable or unsafe through shorting or other loss of insulation effectiveness (indicated by the second digit being "1"). The third digit is often not specified.
The first number defines the level of protection against penetration of solid objects into the housing.
Example: - scored a 5 out of 6
The second number defines the level of protection against penetration of liquids into the housing.
Example -ROCKY scored 4 out of 8
Additional information can be found in the 1976 IEC Publication,
Classification of Degrees of Protection Provided by Enclosures.
Number / Degree of Protection / Number / Degree of Protection
0 / No protection against contact or
entry of solids. / 0 / No protection.
1 / Protection against accidental
contact by hand, but not deliberate
contact. Protection against large
objects. (greater than 50mm) / 1 / Protection against drops of condensed
water. Condensed water falling on housing
shall have no effect.
2 / Protection against contact by fingers.
Protection against medium-size foreign
objects. (greater than 12mm) / 2 / Protection against drops of liquid.
Drops of falling liquid shall have no
effect when housing is tilted to 15
degrees from vertical.
3 / Protection against contact by tools,
wire, etc. Protection against small
foreign objects.(greater than 2.5mm) / 3 / Protection against rain. No harmful
effect from rain at angle less than 60
degrees from vertical.
4 / Protection against contact by small
tools and wires. Protection against
small foreign objects. (greater than
1mm) / 4 / Protection against splashing from any
direction.
5 / Complete protection against contact
with live or moving parts. Protection
against harmful deposits of dust. / 5 / Protection against water jets from any
direction.
6 / Complete protection of live or moving
parts. Protection against penetration
of dust. / 6 / Protection against conditions on ships'
decks. Water from heavy seas will
not enter.
7 / Protection against immersion in water.
Water will not enter under stated
conditions of pressure and time.
8 / Protection against indefinite immersion
in water under a specified pressure.
Dust protection
First characteristic
numeral / Brief
description
0 / Non-protected
1 / Protected against solid objects greater than 50mm
2 / Protected against solid objects greater than 12.5mm
3 / Protected against solid objects greater than 2.5mm
4 / Protected against solid objects greater than 1mm
5 / Dust-protected
6 / Dust tight
/ Water protection
Second characteristic
numeral / Brief
description
0 / Non-protected
1 / Protected against dripping water
2 / Protected against dripping water when tilted up to 15°
3 / Protected against spraying water
4 / Protected against splashing water
5 / Protected against water jets
6 / Protected against heavy seas
7 / Protected against the effects of immersion
8 / Protected against submersion
The IP Rating often includes a third digit denoting impact resistance.