When are Occupancy Sensors Mandatory? (Energy Conservation Code: Section C405)

BMoran242

New User
Location
Raleigh, NC
Occupation
Electrical Engineer
I have been trying to understand the relationship between C405.2.1 Occupant sensor controls and C405.2.2 Time-switch controls.
To me, it reads as though all rooms listed in C405.2.1 must have OS and room types not listed there can instead implement OS or Time-switch controls, but many of the colleagues believe it is an either-or option.

For example, "Classrooms/lecture/training rooms" is the first listed in C405.2.1
To me, this means that it is mandatory to use OS in these rooms, outside of the given exceptions, but many of my colleagues believe that using C405.2.2 Time-switch controls is an acceptable alternative to C405.2.1 Occupant sensor controls.

C405.2.1.3 Occupant sensor control function in open plan office areas, is not part of the 2018 NC Energy Code, but it will be a part of 2024. Here it specifically gives an exception for part 3, allowing open plan office areas to use Time-switch controls for turning lights off.
If C405.2.2 was an acceptable alternative to C405.2.1, then I do not understand why this exception would be included, as it is the exact situation our internal discussion is about.

Am I missing something here? Are you allowed to use Time-switch controls instead of OS in rooms listed in C405.2.1? Or is C405.2.2 only acceptable for rooms not listed in C405.2.1?
 
A campus I work on had to comply with this recently;
The parent section C405.2 Lighting Controls states you pick one;
Lighting systems shall be provided with controls that comply with one of the following.

1 Lighting controls as specified in Sections C405.2.1 through C405.2.7.
or
2 Luminaire level lighting controls (LLLC) and lighting controls as specified in Sections C405.2.1, C405.2.5 and C405.2.6. .....
 
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