UL (UNDERWRITERS LABORATORIES):
An independent organization with main headquarters on the north side of Chicago. They create and publish Standards primarily purposed to ensure safety most predominantly from fire, explosion, and electrocution. Their Standards do not address performance except in so far as it might affect safety.
The Industrial Control Panels Standard UL508A, Edition 3, dated April 24, 2018 is now certified under ANSI ( American National Standards Institute – see below) and took affect from July 2020. It is normally the users of the panel who will require (or not) conformance to UL 508A. The “users” here can be looked upon as the chain linking the electrical industrial control panel supplier to the final installation. The OEM (such as a machine builder), the actual installation site owners (such as a factory or plant), and the AHJ (the authority having jurisdiction – such as a local municipal government body, or a fire-chief).
Most industrial control components (and conductors) that are made for widespread distribution for the USA market will have been certified individually to some level according to the relevant (and ANSI certified) UL Standard, and will be catalogued, and will come out of the box, marked as such. An Industrial Control Panel, when required to be, could as a whole be marked to show it’s conformance with UL 508A. Some panels may fail inspections if not designed specifically to the corresponding Standard, (as examples:
- special component used that did not have any UL component certification;
- wrong size short circuit protection component;
- wrong size conductor;
- UL RECOGNIZED component not used according to conditions set by UL;
- UL (fully) LISTED component yet not in correct category for UL 508A panel. )
UL also has extensive testing facilities where it develops the conditions for the Standards and verifies components and whole panels. It will also conduct special tests to certify equipment for compliance to specific requirements (such as compliance to Standards for special use applications – like renewable energy to grid inverters, or to verify overall Short Circuit Current Rating of a completely assembled panel). As such UL acts as an NRTL (Nationally Recognized Testing Laboratory). There are other NRTLs in the USA quite independent of UL such as Intertek and MET. They offer similar testing in sites in other parts of the country. They test for conformance with the UL written Standards. In this respect, they are an alternative to UL for their customers and could also have different charges and may make different judgements.
NFPA (NATIONAL FIRE PROTECTION ASSOCIATION):
This organization is non-profit. They do not conduct tests nor inspections. Similarly to UL, they are concerned with the danger of fire and the other safety issues, but do not intend to address performance. They write standards by bringing together viewpoints of volunteers and get the approval of ANSI (see below). NFPA Standards are looked upon as regulation in the USA, most notably NFPA 70 which is referred to as the National Electrical Code (NEC). NFPA 79 is the Standard “Electrical Standard for Industrial Machinery”. This latter Standard is relevant for Industrial Control Panels as it defines for a particular machine installation what is required between the panel and other panels and the machine itself. UL 508A, when applied, would override stipulations inside the panel including connection points and inside circuits – one example of a difference (where UL 508A is stricter):- conductors inside need to have 90 Co insulation but be rated to run at 75 Co max.
NFPA 70 is referred to as the National Electric Code (NEC). It applies to all general practices in the wider environment including household for example and may impose additional regulations corresponding to the possible exposure of unskilled persons.
UL
ANSI (AMERICAN NATIONAL STANDARD INSTITUTE):
ANSI is the senior and overall authority for all USA Standards in all sectors of industrial practice and regulation. It also represents the USA internationally with membership in ISO (International Organization for Standardization). In the USA, it evaluates Standards written by others and certifies some of them, but not all.
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