If you answered the National Electrical Code, you would be partially correct. Manufactured housing has its own set of construction standards that are found in 24 CFR Part 3280. This came into being in response to the National Manufactured Construction and Safety Standards Act of 1974 (42 U.S.C. 5403). These original rules were, for the most part, transcribed from the 1977 edition of NFPA 501B, Standard for Mobile Homes. This standard was withdrawn by the NFPA in 1979 because of the preemptive nature of 24 CFR Part 3280 and HUD showed no interest in having the private sector continue the development and maintenance of manufactured housing standards at that time. During the hearings of the National Commission on Manufactured Housing in the early 1990s, the NFPA expressed interest in managing the development of the manufactured housing standard once again, and in 1995 elected to update the previous edition (1977) of NFPA 501B. This resulted in the 1997 edition of NFPA 501, Standard on Manufactured Housing. The National Technology and Transfer Act of 1995 includes as one of its goals the requirement for federal agencies to “…use technical standards that are developed or adopted by voluntary consensus standard bodies…” The NFPA submitted a statement of interest to HUD to assume responsibility for the development and maintenance of standards for manufactured housing and was selected by HUD as a consensus standard development organization. It is interesting to note that while selected by HUD, there is no obligation by HUD to use the standards developed by the NFPA and this selection does not preclude any other individual or entity from making recommendations to HUD regarding the manufactured housing program standards.
As a result of the selection, NFPA established a technical correlating committee (TCC) to manage the project with six separate technical committees (TC) reporting to the TCC. The 1997 edition was up-dated as the 1999 edition, which was then placed on an expedited cycle which resulted in the 2000 edition of NFPA 501.
Now that you have more background information than you probably wanted, where does the NEC fit into this picture? Well, keep in mind that NFPA 501 was developed with the intent that it would be adopted as the construction standards in 24 CFR Part 3280. Paragraph 9.1.1 of NFPA 501 states that “this chapter and Part A of Article 550 of NFPA 70, National Electrical Code, shall apply to the electrical conductors and equipment installed within or on manufactured homes and the conductors that connect manufactured homes to a supply of electricity.” Revisions were made to the 2000 edition of NFPA 501 and proposals to revise the 2002 NEC have been submitted, so the two documents will be identical. Those portions of the documents that pertain to the construction of the manufactured home itself should not be in conflict. NFPA 501 at Paragraph 9.1.2 further states that “in addition to the requirements of this standard and Article 550 of NFPA 70, National Electrical Code, the applicable portions of other articles of the National Electrical Code that cover electrical installations in manufactured homes shall be followed. When-ever the requirements of this standard differ from the requirements of the National Electrical Code, this standard shall apply.” This, in effect, sets NFPA 501 as the primary document for manufactured home construction standards.
There are some minor differences between the requirements for manufactured housing versus “stick-built” homes, mainly in where receptacle outlets are required. The federal rules mandate a cost/benefit analysis and where safety is not compromised, this can account for some of the differences.
It is the hope of Code Making Panel 19 that we will continue to work with the NFPA 501 Technical Committee on Electric to produce one standard set of rules that a manufacturer or installer can use without conflicts to ensure the continued safety of manufactured housing.