Almost every commercial LED fixture you pull out of a box has two extra wires, usually purple and gray. That is 0-10V dimming. It is the standard way to dim commercial LED, and it works very differently from the Triac dimmers most people know from houses.
How 0-10V works
A 0-10V fixture has two separate circuits. The line voltage (black, white and ground) powers the driver. The low voltage dim pair tells the driver how bright to run. The driver puts out a small DC voltage on the dim pair, and the dimmer or control pulls that voltage down to dim the fixture.
- About 10V on the dim pair means full output.
- Lower voltage means lower output.
- At or near 0V to 1V the driver runs at its minimum level, typically around 10% or 1% depending on the driver.
0-10V does not turn the light off. At the bottom of the range the fixture is still on at minimum. To turn it off you need to switch the line voltage, which is why most 0-10V wall dimmers have a built in on/off switch or relay.
0-10V vs Triac
| 0-10V | Triac (phase cut) | |
|---|---|---|
| How it dims | Separate low voltage control signal | Chops the line voltage waveform |
| Wiring | Line voltage plus a 2 wire dim pair | Dimmer in series with the line, no extra wires |
| Where it is common | Commercial and industrial fixtures | Residential, screw in lamps, some downlights |
| Many fixtures on one dimmer | Yes, up to the dimmer's rated capacity | Limited by dimmer load rating and compatibility |
| Works with sensors and building controls | Yes, the standard for commercial controls | Limited |
Do not put a Triac dimmer on a 0-10V driver. The driver is not designed for a chopped input, and you can get flicker, buzzing or a damaged driver. Check the spec sheet. If it says 0-10V, use a 0-10V control.
Wiring the purple and gray leads
- Purple (or violet) is DIM +. Connect it to the dimmer's purple or + lead.
- Gray is DIM minus. Connect it to the dimmer's gray or minus lead. Some fixtures use pink instead of gray.
- Polarity matters. Reverse them and the fixture typically stays at full brightness or will not dim.
- Never connect the dim leads to line voltage. That will typically destroy the driver.
- Not dimming? Cap them separately. If the job has no dimming, cap the purple and gray individually and do not tie them together, which typically drops the fixture to minimum.
- Daisy chain in parallel. Run purple to purple and gray to gray across fixtures on the same zone.
The dim pair is a low voltage control circuit. Follow the NEC and local code for routing it with or apart from line voltage conductors. Many installers use dim conductors rated for the same voltage as the power conductors when they share a raceway. When in doubt, check with the inspector.
Sizing the dimmer
Each 0-10V dimmer can only handle so many drivers on its control signal, and its built in switch has a load rating. Check both: the control capacity listed by the dimmer maker, and the line voltage load in watts or amps. On big zones, use a relay or power pack to switch the load and let the dimmer just send the signal.
Controls that use 0-10V
- Wall dimmers with on/off and a slider or paddle.
- Occupancy sensors that dim to a low level when a space is empty. See PIR, microwave and dual tech sensors.
- Daylight sensors that dim fixtures near windows or skylights.
- Timers and building automation that set levels by schedule.
Many fixtures accept plug in or integrated sensors, and you can find add ons in sensors and accessories or shop fixtures with an occupancy sensor already built in. Most high bays, flat panels and strip lights come with 0-10V standard.
Controls can also help with rebates, since some programs pay extra for sensors. Find out if there are rebates in your area.
Shop sensors and accessories
0-10V compatible sensors and add ons for commercial LED fixtures, at contractor pricing.
Shop sensors