A common misconception among greenhouse growers and indoor farmers is that ground-fault circuit interrupters (GFCIs) are not required for horticultural lighting. This misunderstanding often arises from an incorrect interpretation of the NEC Section 547, which provides specific guidelines for agricultural buildings. However, it’s essential to clarify that this section does not exempt horticultural lighting from GFCI requirements.
Understanding the Requirements
The 2023 NEC® Section 410.184 specifically mandates GFCI protection for outlets supplying lighting equipment identified for horticultural use that employ a flexible cord with one or more conductors. The exact text states:
NEC Section 410.184: “Lighting equipment identified for horticultural use employing flexible cord(s) with one or more conductor(s) or attachment plug(s) shall be supplied by lighting outlets protected by a listed GFCI.”
This requirement specifically identifies horticulture LEDs and is aimed at ensuring safety in greenhouses and indoor farms, environments where water and electricity are in close proximity.
Common Misconception and NEC Section 547
A common misconception among growers is that NEC Article 547 exempts them from this electrical requirement. But why would the NEC specify the need for GFCIs only to exempt horticulture LEDs from GFCIs in another section? They wouldn’t. Article 547 specifically targets toward agricultural buildings used for livestock, poultry, and other animal confinement and does not mention greenhouses or indoor farms. The unique conditions within greenhouses, such as high humidity and frequent water exposure, necessitate stringent electrical safety measures. Fires are common, and greenhouse workers have died from electrocution, resulting in substantial penalties for owners. Reducing these risks is the intent of the GFCI requirements, and Article 547 does not provide exemptions for greenhouse environments.
Practical Considerations for Growers
Growers must adhere to GFCI requirements unless they opt for an alternative, less flexible installation method. One such method is hardwiring the LEDs, eliminating the need for GFCIs. The NEC specifies that any use of flexible cable requires GFCI protection. Hardwiring typically means not using a plug. Therefore, the only way to avoid the GFCI requirement is to use MC cable or conduit.
It’s important to note that flexible cables cannot be hardwired directly unless they either have a connector, which necessitates the use of a GFCI, or are equipped with a disconnect device within reach of someone working on the fixture. Additionally, flexible cables cannot be concealed behind walls or ceilings. They must not pass through a hole in the ceiling without being enclosed in conduit, ensuring that all wiring is properly protected and accessible for maintenance.
The trade-off is that each time a hardwired fixture needs to be serviced, moved, or changed an electrician must be called in. The cost of this inflexibility often motivates growers to use GFCIs.
GFCI Challenges
Still, GFCI’s impose other limits on overall efficiency. For instance, sourcing GFCIs rated for 277VAC is often difficult and expensive. This leads growers to add transformers to decrease the voltage to 208VAC or 240VAC, which can increase costs and reduce distribution efficiency.
Centralizing LED drivers outside of grow spaces offers many CAPEX and OPEX benefits. See to learn more about those benefits. But no GFCI is rated for DC power, so using remote, high-voltage necessitates hardwiring LEDs and adding local disconnects, which results in cost levels that make that option unappealing.
How to Avoid GFCIs Without Hardwiring LEDs
There is one solution for avoiding the need for GFCIs without resorting to hardwiring LEDs. That is using Digital Electricity™. Digital Electricity is a fault-managed power system listed as a “Limited Power Source.” That means it is the only high-voltage electrical distribution system that can be installed using low-voltage wiring methods. So even though Digital Electricity allows you to distribute 336VDC directly to horticultural LEDs, GFCIs and hardwiring are not required under the National Electric Code (NEC).
Moreover, Digital Electricity eliminates the need for LED drivers within grow spaces by centralizing them, which enhances reliability, simplifies servicing, and reduces the overall cost of the LED system. This centralized approach also brings additional benefits, such as reduced heat load within the grow space, improved energy efficiency, and streamlined maintenance processes. If you’d like to learn more about removing drivers from grow spaces, please see
By adopting Digital Electricity, growers can achieve a safer, more efficient, cost-effective lighting solution that adheres to NEC standards while maximizing the operational benefits for greenhouse and indoor farming environments.
Conclusion
Greenhouse and indoor farm growers must adhere to the 2023 NEC® Section 410.184, which mandates GFCI protection for horticultural lighting using flexible cords. Despite misconceptions, NEC Article 547 does not exempt greenhouses from these requirements. While hardwiring LEDs can eliminate the need for GFCIs, they also introduce inflexibility and higher costs. Digital Electricity offers an innovative solution by enabling high-voltage distribution through low-voltage wiring methods eliminating the need for GFCIs and hardwiring. This system also centralizes LED drivers, enhancing reliability, simplifying maintenance, and reducing overall costs, providing a safer, more efficient lighting solution that complies with NEC standards.
