MH Controls Corner: Update to 0–10V Dimming Protocols

October 04, 2021

Over the last few years, the lighting industry has finally become accustomed to the new 0–10V dimming protocols that have taken a foothold ever since the fluorescent fixtures have rapidly been replaced by the new LED standard. Two-wire dimming is now, more or less, reserved for decorative lighting lines. Bi-level switching applications have mostly all gone to dimming in the commercial lighting world. We have accepted the normalcy of 0–10V dimming to handle most of our standard lighting applications. These installations use five wires total (hot, neutral, ground, and two low voltage control conductors) and have become very commonplace in the commercial lighting industry. However, there have been some recent changes to the standards of 0–10V (5-wire) dimming requirements imposed by the NEC that are worth reviewing.

The National Electric Code, (NFPA-70) section 410.69, disallows the use of circuit or equipment grounding conductor colors (white, grey or green, green/yellow) to be used for control conductors. This in turn led to the proposition that in 5-wire dimming applications, what we have come to accept as Purple and Grey conductors for the low voltage control wires should now be purple and pink. For 277V applications, the ground conductor is typically grey. Having a mix of grey line voltage and grey low voltage conductors in the same box can lead to a bad situation. After some review, NEMA Wire & Cable Section and Lighting Systems Division decided the appropriate change would be to have the grey conductor on the 0–10V wires changed to pink to eliminate any confusion in the field. Although this was written into code in 2020, the NEC decided that this was a disruptive enough change to push back the new requirement a couple of years and let folks catch up. Local jurisdictions that have adopted the 2020 NEC standards should not have to enforce this new requirement until January of 2022.

Manufacturers have been hard at work trying to embrace these new requirements and accommodate their customers, but they also have a big challenge on their hands. The change only applies to jurisdictions that have adopted the new 2020 NEC standard, meaning Purple and Grey will still be commonplace for some time to come. Furthermore, the NEC requirements only apply to field installed wiring and don’t govern manufacturers’ products. Manufacturers are not obligated to adhere to the changes, but rather are encouraged. In the meantime, contractors will have to deal with the brunt of the leg work as the industry rides through this change. Although some manufacturers have already taken the proactive leap, products that are shipped to the field with purple and grey conductors will have to have the grey relabeled as pink to meet the new requirements.

As they say, “the only thing that is constant is change” and this is neither good nor bad, just something to adapt to.

0-10V Installation Tips

Please keep in mind that for testing your 0–10V dimming systems, disconnecting and shorting the purple and grey (pink) conductors together while fixtures are powered up will bring the fixtures down to the lowest dim level the fixture drivers will allow for. Opening the purple and grey (pink) conductors should allow the fixtures to go to full bright. If this is not how the fixtures act under this test then likely there is a wiring issue. Please always run this test prior to connecting these conductors to lighting control components.

This article was written by Mike Bogomolov, our Controls Engineering Supervisor. Mike can be reached at 720.904.8537 or And remember, whenever you have a technical controls question, on any project or application, simply email This email address is monitored by our entire controls team. During our normal business hours, we are committed to a four-hour response time for all emails sent to this email address!