NEC Article 410 Part XVI: Horticultural Lighting

By: Robert Key | Feb 10, 2022

It is difficult to go for a drive or to a shopping center and not notice the prevalence of CBD products available, since many states have legalized or decriminalized CBD, hemp, and even marijuana for use as medicine or recreation. Regardless of how you may feel about their use, large-scale cultivation of these and other plants is now a reality in many areas. Therefore, it was a wise decision by the Code-making panel to create a new section in Article 410, Luminaires, Lampholders, and Lamps, to address the potential electrical hazards arising from horticulture. This new addition to the 2020 NEC provides regulation for equipment specifically identified for horticultural use. 

How does horticulture differ from agriculture?While agriculture is usually associated with large-scale food crops and rearing animals, horticulture typically deals with gardening, such as occurs in nurseries and greenhouses, and usually requires the use of specialized lighting and equipment.  

Why is specialized lighting and equipment needed? Horticultural environments are often wet due to irrigation systems and sit directly on the earth, where they complete an electrical path to ground. A wet environment, grounded to earth, exposes horticultural workers to an increased level of risk, not normally encountered inside of an insulated building. Consider also that much of the commercial lighting equipment will be powered at 277/480 volts or more. Therefore, NEC regulation for the electrical lighting designated for these areas is necessary to fulfill the purpose of the Code, which as we know is, “The practical safeguarding of persons and property from hazards arising from the use of electricity.” 

Let’s look at some of the new horticultural lighting requirements from the 2020 NEC, Section XVI: 

  • Horticultural lighting and systems must be listed and installed and used per manufacturers’ instructions and in accord with their listing. 
  • GFCI protection is required where flexible cords are employed. 
  • Equipment must be supported by fittings specifically identified and designed for the lighting system. 
  • Although these systems can provide lighting for the area in which they are utilized, they cannot be used as general-purpose lighting unless listed for such a purpose. 

The full text of the new section is as follows: 

Part XVI. Special provisions for Horticultural lighting equipment  

410.170 General. 

Luminaires complying with parts I, II, III, IV, V, VI, VII, IX, X, XI, and XII of this article shall be permitted to be used for horticultural lighting. Part XVI shall additionally apply to lighting equipment specifically identified for horticultural use. 

Informational note: Lighting equipment identified for horticultural use is designed to provide a spectral characteristic needed for the growth of plants and can also provide supplemental general illumination within the growing environment. 

410.172 Listing. 

Lighting equipment identified for horticultural use shall be listed. 

410.174 Installation and use. 

Lighting equipment identified for horticultural use shall be installed and used in accordance with the manufacturer’s installation instructions and installation markings on the equipment as required by that listing. 

410.176 Locations Not Permitted. 

(A) General lighting. 

Lighting equipment identified for horticultural use shall not be installed as lighting for general illumination unless such use is indicated in the manufacturer’s instructions. 

(B) Installed location. 

Lighting equipment identified for horticultural use shall not be installed where it is likely to be subject to physical damage or where concealed. 

410.178 Flexible Cord. 

Flexible cord shall only be permitted when provided as part of listed lighting equipment identified for horticultural use for any of the following uses: 

  • Connecting a horticultural lighting luminaire directly to a branch circuit outlet. 
  • Interconnecting horticultural lighting luminaires. 
  • Connecting a horticultural lighting luminaire to a *remote power source. 

Informational note: *remote power sources include LED drivers, fluorescent ballasts, or HID ballasts. 

410.180 Fittings and Connectors. 

Fittings and connectors attached to flexible cords shall be provided as part of a listed horticultural lighting equipment device or system and installed in accordance with the instructions provided as part of that listing. 

410.182 Grounding. 

Lighting equipment identified for horticultural use shall be grounded as required in Article 250 and part V of this article. 

410.184 Ground-Fault Circuit-Interrupter Protection. 

Lighting equipment identified for horticultural use employing flexible cords with one or more conductors shall be supplied by lighting outlets protected by a listed ground-fault circuit interrupter. 

410.186 Support. 

Special fittings identified for support of horticultural lighting equipment shall be designed specifically for the horticultural lighting equipment on which they are installed and shall be used in accordance with the installation instructions provided and shall be securely fastened. 

410.188 Hazardous (Classified) Locations. 

Where installed in hazardous (classified) locations, horticultural lighting equipment shall conform to Articles 500 through 517 in addition to this article. 

As more efficient lighting technologies continue to evolve and more states move towards decriminalization or legalization of hemp, CBD, and marijuana, usage of horticulture-specific lighting is likely to increase. The new Code sections cover many common topics such as listing, support, grounding, uses not permitted, and GFCI protection. The electrician and AHJ will no longer have to guess as to the application of the Code for this type of installation.


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