210.70(A)(2)(4) Lighting Outlets Required. Additional Locations.
Code Change Summary: Additional code language clarifies the use of dimmer switches at interior stairways.
Section 210.70(A)(2) provides additional rules on dwelling unit lighting outlets. This is the section of the NEC® that requires lighting outlets in hallways, stairways, and garages with electric power.
The general rule for an interior stairway is to have at least one wall switch–controlled lighting outlet serving the stairs. If the interior stairway between floor levels has six risers or more, a wall switch is required at each floor level, and landing level that includes an entryway.
Until now, there has been no specific rule about dimmer switches used at interior stairwells. In the 2017 NEC®, the use of dimmer switches at interior stairways is permitted as long as the switch can be adjusted to full brightness at each switch location. The idea is to avoid a situation where a dimmer is adjusted to the lowest illumination level at one end of the stairs and cannot be adjusted at the other end.
A 3-way snap switch at the top of the stairs doesn’t do much good if someone set the 3-way dimmer at the bottom of the stairs at the lowest illumination level. The only way to turn up the dimmer so that the stairs are properly illuminated is to attempt to make it to the bottom of the stairs in the dark to reach the only dimmer switch.
Below is a preview of Article 210. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.
2014 Code Language:
210.70(A)(2)(4) Additional Locations. Additional lighting outlets shall be installed in accordance with (A)(2)(a), (A)(2)(b), and (A)(2)(c).
(a) At least one wall switch–controlled lighting outlet shall be installed in hallways, stairways, attached garages, and detached garages with electric power.
(b) For dwelling units, attached garages, and detached garages with electric power, at least one wall switch– controlled lighting outlet shall be installed to provide illumination on the exterior side of outdoor entrances or exits with grade level access. A vehicle door in a garage shall not be considered as an outdoor entrance or exit.
(c) Where one or more lighting outlet(s) are installed for interior stairways, there shall be a wall switch at each floor level, and landing level that includes an entryway, to control the lighting outlet(s) where the stairway between floor levels has six risers or more.
2017 Code Language:
210.70(A)(2)(4) Additional Locations. Additional lighting outlets shall be installed in accordance with the following:
(1) At least one wall switch–controlled lighting outlet shall be installed in hallways, stairways, attached garages, and detached garages with electric power.
(2) For dwelling units, attached garages, and detached garages with electric power, at least one wall switch– controlled lighting outlet shall be installed to provide illumination on the exterior side of outdoor entrances or exits with grade-level access. A vehicle door in a garage shall not be considered as an outdoor entrance or exit.
(3) Where one or more lighting outlet(s) are installed for interior stairways, there shall be a wall switch at each floor level, and landing level that includes an entryway, to control the lighting outlet(s) where the stairway between floor levels has six risers or more.
(4) Lighting outlets controlled in accordance with 210.70(A)(2)(3) shall not be controlled by use of dimmer switches unless they provide the full range of dimming control at each location.