Sagot :
Answer:
Grounding Switch Plates
The metal mounting yokes for switches, dimmers, and similar control switches must be connected to an EGC of a type recognized in 250.118, whether or not a metal faceplate is installed [404.9(B)] (click here to see Fig. 3).
A few years ago, a listed switch constructed entirely of plastic entered the market. These switches don’t allow a metallic faceplate to be installed on them. Because a plastic (nonconductive) component is inherently safer than a metal component connected to an EGC, a new exception allows for this product [404.9(B), Ex 2].
Another exception addresses the use of wiring devices with integral enclosures. Similar to the switches discussed above, these have nonmetallic faceplates and don’t allow for the attachment of metallic ones [404.9(B), Ex 3].
Receptacle Replacements
Receptacle requirements are in Art. 406 (see Article 406 on page 29). New requirements have been added for the replacement of receptacles to address replacements in areas requiring AFCI protection, tamper-resistant receptacles, or weather-resistant receptacles [406.4(D)].
As aging wiring systems have become a growing concern in the electrical industry, the Code is taking a proactive approach to providing protection of these systems. Many areas of a dwelling now require the use of AFCI protection to help avoid electrical fires.
When AFCIs were first introduced into the NEC, the substantiation for their inclusion was based largely on electrical fires in older homes. However, the Code began by protecting new and future wiring systems but didn’t address the older ones that contained many of the fires discussed in the AFCI arguments. The 2011 NEC expands the AFCI requirements to older homes. Because older homes often don’t contain an EGC, installation of an AFCI circuit breaker does little in the way of protecting the branch circuits. The receptacle-type AFCIs also provide a significantly lower level of protection, but they will be required nonetheless.
The 2008 NEC introduced the concept of tamper-resistant receptacles in dwelling units. The requirements of that section (406.11, now 406.12) apply to new installations. The 2011 Code now also requires that on existing dwelling units, any receptacles that are replaced will be replaced with tamper-resistant receptacles.
A similar change was made for weather-resistant receptacles, using the same logic as that used for tamper-resistant receptacles.
Wet Locations
For receptacles in wet locations, the 2011 Code includes a new requirement for “extra-duty outlet box hoods” [406.9(B)(1)]. All 15A and 20A receptacles installed in a wet location must be within an enclosure that’s weather-proof when an attachment plug is inserted. For other than one- or two-family dwellings, the outlet box hood must be listed for “extra-duty” use if supported from grade (click here to see Fig. 4). All nonlocking type 15A and 20A, 125V and 250V receptacles in a wet location must be listed as weather resistant.
Exposed plastic surface material of weather-resistant receptacles must have UV resistance to ensure that deterioration from sunlight is minimal or prevented. In testing, receptacles are subjected to temperature cycling from very cold to very warm conditions, and then subjected to additional dielectric testing. The rapid transition from the cold to warm temperatures will change the relative humidity and moisture content on the device. The dielectric test ensures that this won’t create a breakdown of the insulation properties.
Exception: Receptacles rated 15A and 20A that are subjected to routine high-pressure washing spray may have an enclosure that’s weatherproof when the attachment plug is removed.
Explanation: