Todd Thompson - Construction Manager - 2M CCTV
There is some confusion about the technical ratings of enclosures for electronic components. In an earlier article, we provided information and a chart for decoding the IP ratings on a given assembly (you'll find a NEMA ratings chart at the bottom of this article). Here, we want to go a step further and explain what NEMA Ratings are and how, if at all, it is related to IP ratings.
Who is NEMA?
The National Electrical Manufacturing Association (NEMA) is an association that is voluntary. It is not a policing organization, and it has neither the authority, nor jurisdiction, to support or refute the claims of manufacturers of electronics enclosures. As stated in its white paper, A Brief Comparison of NEMA 250 and IEC 60529, NEMA publications of standards and guidelines provide a consensus view of relevant interested parties. NEMA does not independently test, evaluate, or verify the standards set forth in its publication.
With the disclaimer out of the way, the question may be asked,Then what good is a NEMA rating?
NEMA ratings and responsible manufacturers
Keeping in mind that associations set such standards for the use of its members, the voluntary nature of the association puts the onus of proof directly on the manufacturer.
Manufacturers want to control risk and stay out of the fray of product liability lawsuits. It would be unwise, nonsense, for a manufacturer that wants both a growing market and minimal loss to claim a product has certain physical qualities that have not been tested adequately, either by their own testing facilities, or by an independent testing company.
NEMA provides the guidelines for independent manufacturers and testing labs. This ensures consumers have the resources of the manufacturer or testing laboratory should there be a need for recourse down the road.
What do the NEMA guidelines provide?
The NEMA ratings that are seen on product specification documents are intended to advise the customer of the relative protection an enclosure offers against intrusion by foreign substances or environmental conditions.
Additionally, the NEMA rating is the manufacturer's claim with regard to the relative degree of protection the enclosure offers. It refers to the camera body, the box or dome, for example. It is separate from a guarantee.
Unless the manufacturer guarantees its claims, there is little recourse for the customer in the event of a failure. NEMA would leave the customer holding the bag as it cannot force compliance by the manufacturer or even verify the manufacturer's claims.
How do the NEMA guidelines relate to IP ratings?
IP ratings are intended to provide guidance on the degree of protection against the intrusion of solid foreign objects and water as well as the protection the enclosure offers to persons from the hazardous parts inside of it. In other words, IP ratings do not cover the hazards of environmental conditions such as gas exposure, acidic atmospheric conditions, corrosives, the effects of icing.
NEMA, for instance, gives guidance on the security of the doors or covers on an enclosure. It also gives construction requirements so that those who install NEMA enclosures will uphold the rating instead of devaluing it by using materials or methods that compromise it.
IP ratings can be viewed as cousins to NEMA ratings. They are related in the sense that both IP and NEMA provide product selection guidance. However, the two ratings are different in scope.
IP ratings are limited to the three areas of protection: human, water, and solid foreign objects. NEMA includes specifications for construction. NEMA ratings provide advice for conditions like icing, oil, gasket deterioration, and other similar hazards. In other words, NEMA's scope is broader than the IP ratings.
Is it possible to determine equivalent ratings between IP and NEMA?
While NEMA provides enough guidance that an equivalent IP rating may be determined, equivalents are not really possible. IP ratings will not help a customer to determine an equivalency to a NEMA rating. NEMA ratings require other hazards or conditions to be considered. IP, for example, does not address corrosion standards.
Which is better for the consumer?
Honestly, the NEMA rating is more important for consumers who intend to install electronics in conditions that may include icing, acids, corrosives, oil, or tampering.
Keep in mind, though, the manufacturer who claims a NEMA rating will have to stand by that designation without any help from the National Electrical Manufacturers Association. This means that manufacturers will be reluctant, if they are wise, before listing a NEMA rating in their product literature.
An IP rating should be sufficient in relatively normal environmental conditions, but when dealing with anything out of the ordinary, environmentally speaking, look for the NEMA enclosure rating, if you want to breathe more easily.
NEMA Ratings Chart demonstrating each number/type with illustrated examples of enclosure protection. Below illustrations are for Non-Hazardous locations only.