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National Electrical Code Articles and Information

Based on the 2020 NEC

by Mark Lamendola

National Electrical Code Top Ten Tips: Article 545, Manufactured Buildings

  1. Prior to the 2020 revision, Article 545 took up less than a full page and was among the shortest of NEC articles. With the 2020 revision, it also covers relocatable structures; those requirements are Part II. This added material about doubled the size of Article 545. The buildings it covers are still subject to the first four Chapters of the NEC. Article 110 is especially important in this regard.
  2. Article 545 covers not just manufactured buildings, but also their components. It covers not just relocatable structures, but also their supply conductors [545.1].
  3. You can use any raceway or cable wiring method in the NEC (those are listed in Chapter 3) and other wiring systems specifically intended and listed for use in manufactured buildings [545.4(A)].
  4.  Closed construction is where the building or component is manufactured such that it isn't possible to inspect those after installation without disassembly, damage, or destruction [545.2].
  5. In closed construction, you can secure cables only at cabinets, boxes, or fittings where 10AWG or smaler conductors are used and protection against physical damage is provided [545.4(B)].
  6. You can't preinstall the service entrance conductors. They must be installed after erection at the building site [545.6]. This does not prohibit such practices as kitting or precutting and prelabeling conductors.
  7. You must protect conductors during erection at the building site (and also during transit to the site) [545.8].
  8. Any box not over 100 cubic inches in size and intended for mounting in closed construction must be affixed with anchors or clamps to provide a rigid and secure installation [545.9(B)].
  9. The manufacturer is required to make provision for bonding all prewired panels and building components; make sure you make the proper connections to the terminals or other bonding provisions [545.11]. The manufacturer is required to make provision for routing a grounding electrode conductor from the supply to the point of attachment to the grounding electrode [545.12]. Do not confuse this with the bonding system; see the Article 100 definitions related to grounding and bonding.
  10. Relocatable structures are covered in Part II. One highlight is the relocatable structure must have a single disconnecting means in an accessible location [545.24(A)].