What a Title 24 Lighting Control Device Must Do

Installing the right kind of control is only half of it — the device itself has to meet specifications. Dimmers must cut power by at least 65 per cent, occupant sensors must act within 20 minutes, and time switches need 7-day program backup.

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 health and usability requirement rather than an energy one. It is in the Energy Code because the code is what specifies dimming, and a dimmer that saves energy while making a space unpleasant to occupy has not helped.

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 of backup

Automatic and astronomical time-switch controls must have program backup preventing loss of the device's schedule for at least 7 days, and of its date and time.

Seven days is chosen deliberately: it covers a long weekend plus a public holiday. 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.