Dynamic elaboration on the Art & Science of Hazardous Area Protection
Ex & degrees of Protection (IP) according to IEC 60529 in comparison to NEMA Enclosure-Types.
A system for classifying the degrees of protection provided by the enclosures of Electrical Equipment
Definition of protection includes:
The overall object of this system is to promote uniformity in methods of describing the protection provided by the enclosures through a structured CODE, known as IP CODE or IP INDEX, which is documented and implemented through a series of tests.
Enclosures for “versatile” application indicated in the last column shall meet requirements for
exposure to both water jets and temporary or continuous immersion.
Enclosures for “restricted” application indicated in the last column are considered suitable
only for the conditions to which they were tested.
The IP index is established through a series of tests , using high precision tets devices as documented in IEC 60529 .
For example , see the following schematic of DRIP TEST device. (Ref: IEC 60529)
NEMA is National Electrical Manufacturers Association (of USA).
NEMA Publication 250-2008 defines the descriptions, applications, features ,test criteria, and design tests of all NEMA-type enclosures
Following is the list of described test in Publication 250.
( This list is shared by IEC 60529 ……….BUT with a BIG DIFFERENCE)
The described tests are interesting due to the fact that there are following additional tests which are NOT required for IEC rating :-
Following Table can be used to carry out a comparison of the Type of enclosures from IP ‘s perspective.
To use this table , follow the procedure explained through an example.(Reference: IHS STANDARDS STORE)
An IEC IP 45 Enclosure Rating is specified. What NEMA Type Enclosures meet and exceed the IP 45 rating?
Referencing the first character, 4, in the IP rating and the row designated “IP4_” in the leftmost column in the table;
Follow the RED LINE for NEMA Types 3, 3X, 3S, 3SX, 4, 4X, 5, 6, 6P, 12, 12K, and 13 . These NEMA ratings meet and exceed the IEC protection requirements against access to hazardous parts and solid foreign objects.
Now Follow the GREEN LINE .Referencing the second character, 5, in the IP rating and the row designated “IP_5” in the rightmost column in the table; NEMA Types 3, 3X, 3S, 3SX, 4, 4X, 6, and 6P are selected. These NEMA ratings meet and exceed the IEC requirements for protection against the ingress of water.
As we can see that “NEMA Enclosure Type 5” does not meet the IP 45 protection
requirements against the ingress of water. Likewise NEMA Type 12, 12K and 13 enclosures indicates that these enclosures do not meet the IP45 requirements for protection against the ingress of water.
Only Types 3, 3X, 3S, 3SX,4, 4X, 6, and 6P could be used in an IP45 application.
(Reference : IEC 60529 Edition 2.2)
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