I recently encountered the term "Local Amendments" in responses written by Tester101 and Ed Beal. I would like to know what they meant by this.
Building codes (including the NEC and many others covering a variety of subjects) are usually written by independent organizations who specialize in the subject.
Local laws are passed by governments. Since local politicians are generally not electricians / structural engineers / fire marshals etc, they "adopt" the 3rd party codes by requiring all local construction to comply with them. But sometimes for various reasons the government wants to make additional requirements or changes, e.g. to take into account local conditions, additional safety, historical reasons, etc. They can change the code in any way they want, maybe prohibiting something they feel is risky or allowing something that would normally be prohibited. Or maybe they just change the wording or definitions a bit to clarify or be consistent with other local laws.
In the USA, building codes are often selected by state government, although local cities and counties may have additional rules they require. Note that every state has their own building codes, which is why you must look up the rules for your specific location. Even states that adopt the NEC (which is most of them, but not all) may use different versions. E.g. here is the current NEC adoption, as of September 1 2015:
The changes themselves can be minor and pedantic or major. For an example, here is the Massachusetts electrical code. Note that it starts by saying the code is the 2014 National Electrical Code, with a number of changes.
The National Electric Code (NEC), also known as NFPA-70, is published by NFPA (National Fire Protection Association). NFPA is a non-governmental standards development organization; their published codes and standards are not enforceable.
Not enforceable until a government code enforcment agency adopts them (or portions of them) as the legal code. If you look up the electrical code for the state you live in, you may find that only portions of the NEC are actually adopted into the state code (such is the case in California, where I live). So, in addition to the state code, your local code enforcement agency or AHJ (Agency Having Jurisdiction) is free to add additional requirements, though these would rarely contradict higher level code authority.
Pretty much what it says. A state or perhaps city/town will adopt a verson of the NEC, but with various amendments, strike-throughs, alterations, sections of prior code etc.
i.e. for Vermont, starting on page 8 of this document, a series of amendments to the 2014 NEC for the State of Vermont making it the 2014 NEC as adopted in Vermont. The list is quite short, only extending onto page 9.
I'll include the first two changes from that document:
NFPA 70, National Electrical Code, (2014 edition) To meet the needs of Vermont, NFPA 70 is amended as follows:
-amend- article 100, definitions:
Structure: That which is built or constructed. A pole, pedestal or similar support used exclusively for a utility meter enclosures or combination meter overcurrent device enclosures shall not be considered to be a structure.
-delete and replace as follows- article 110.3(A)(1):
(1) Suitability for installation and use in conformity with the provisions of this code as evidenced by listing or labeling by a nationally recognized testing laboratory.
each state has code "revisions" most times stricter than the NEC but some times the state doesnot use sections of the code a good example if this is NEC started requiring arc fault on the 2011 code revision but Oregon did not adopt them until this last code update 2014, NEC updates the code every 3 years