What a Title 24 Lighting Control Device Must Do

Two different questions

Most of the lighting code says which controls a project must have — occupant sensing here, daylighting there, multilevel in a space over a certain size. This section is different: it says what the device you install has to be capable of.

Both have to be satisfied. Fitting an occupant sensor in every required location does not comply if the sensors cannot do what the code requires of a sensor.

Dimmers: three separate requirements

A control providing dimming must:

• reduce lighting power consumption by a minimum of 65 per cent at its lowest setting
• provide reduced flicker operation
• provide an offset setting producing zero lumen output

The 65 per cent figure is about power, not about perceived light. And note the third item — a dimmer must be able to reach genuine zero, not merely a dim glow, which is what makes dimming equivalent to off where the code allows dimming instead of switching.

Reduced flicker is a usability requirement rather than an energy one. Section 110.9(b)3B defines it as an amplitude modulation of the light output below 30 percent for frequencies under 200 Hz, without causing premature lamp failure, so a dimmer that saves energy while making a space unpleasant to occupy does not comply.

Occupant sensors: 20 minutes, and the grace period

Occupant sensing controls — occupant sensors, motion sensors and vacancy sensors, including those with a partial-ON or partial-OFF function — must be capable of turning the controlled lights off or down no more than 20 minutes after the area has been vacated.

Then the detail almost nobody knows. A manual-on control must have a grace period of no less than 15 and no more than 30 seconds in which lighting comes on automatically after the sensor has timed out. That is the fix for the most annoying failure mode in occupancy sensing: the lights drop while you are still in the room, and you have to find the switch. Within that window, movement brings them back by itself.

Sensors must also provide a visible status signal showing the device is operating properly — which is what makes a fault diagnosable rather than merely irritating.

Time switches: 7 days for the schedule, 72 hours for the clock

Section 110.9(b)1 applies to every control that provides time-switch functionality, including automatic and astronomical time-switch controls. It must have program backup that prevents the loss of the device's schedule for at least 7 days, and of the device's date and time for at least 72 hours, if power is interrupted.

The two periods differ on purpose. A schedule is the work someone programmed in, so it has to survive a week without power, while the clock only has to survive three days. A control that forgets its schedule during a power cut has effectively stopped complying, and nobody notices until a utility bill arrives showing lights running all night.

Title 20 applies as well

Dimmers must meet all requirements for Dimmer Control devices in the Title 20 Appliance Efficiency Regulations, and occupant, motion and vacancy sensors must meet the applicable Title 20 requirements for their device types.

So a compliant installation depends on both codes at once: Title 20 governs the device as a product sold in California, and this section governs it as a component of a compliant building. A device can satisfy one and not the other.

Where projects come unstuck

Substitution on cost. An occupancy sensor without the grace-period behaviour, or a dimmer that bottoms out at 10 per cent rather than reaching zero, looks identical on a drawing and on the ceiling. It shows up in acceptance testing, which is late and expensive — so this is a submittal review check, not a site check.

Common Title 24 Questions

1. Does replacing commercial lighting trigger Title 24?
2. What is a Title 24 lighting power allowance?
3. What are Title 24 lighting controls?
4. Title 24 for warehouse and high-bay lighting
5. Title 24 for outdoor and site lighting
6. When are automatic daylighting controls required?

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