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  • For Safety’s Sake: NEC 2020 – load calculations

Members of the National Fire Protection Association (NFPA) recently concluded discussions on updating Article 220.12 of the NEC (National Electrical Code) to align with a series of energy codes and to account for higher-efficiency lighting solutions in commercial and healthcare buildings.

Because many of today’s lighting solutions are increasingly energy efficient, lower current demands exist for power systems. These efficiencies necessitate extensive revisions to the calculation table used to determine volt-amperes (VA) per square foot. Many commercial structures today are built to specific energy code editions or a standard established by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). NEC 2020 updates now align the NEC with these energy codes, allowing for easier, more consistent installation in the field.

Not only do changes to Article 220.12 streamline industry codes and standards language, they also help design engineers create load calculations that recognize more efficient lighting loads. This, in my opinion, may result in lower infrastructure costs and help fund enhanced safety solutions. 

Article 220.12’s new load calculations do more to help designers get it right the first time.

Thomas Domitrovich, vice president, technical sales

The 2020 change
 

Changes were made for healthcare and commercial buildings. In healthcare, the NEC’s Code-making Panel 2 (CMP2) removed demand factors from the lighting load calculation. Hospitals are drastically different from the large facilities that were common 40 years ago. Today, the healthcare industry looks to smaller surgical and outpatient facilities, which require a different approach to lighting load calculations. In addition, CMP2 lacked the data from ASHRAE and other organizations needed to validate regulations reducing hospital lighting to 32 percent. Without the data required to permit the reduction, the derating values for hospital lighting were deleted.

In commercial buildings, VA per square foot values were reduced (with some exceptions) to align with occupancy energy codes. Examples of VA per square foot changes include banks from 3.2 to 1.3; hotels and motels from 2 to 1.7; garages from .5 to .3; hospitals from 2 to 1.6; courthouses from 2 to 1.4. Armories and auditoriums were raised from 1 to 1.7.

Also, commercial occupancies now align with those set by ASHRAE. The calculation table includes footnotes that help NEC users understand the change in occupancy-type designations and clarify older vs. newer occupancy types and language translations. Here are some designation examples:

  • Armories and auditoriums, considered gymnasium-type occupancies
  • Lodge rooms, considered similar to hotels and motels
  • Industrial commercial loft buildings, considered manufacturing-type occupancies
  • Banks, considered office-type occupancies
  • Garages and commercial storage, considered parking garage occupancies
  • Clubs, considered restaurant occupancies
  • Barbershops and beauty parlors, considered retail occupancies
  • Stores, considered retail occupancies

The rationale for change
 

While Article 220.12 has changed little since its NEC adoption in 1971, technology and sustainability initiatives have greatly advanced. Because of energy-efficient technologies for structures, LEED and other energy conservation efforts and energy codes and standards updates, the NEC needed to create parity.

Industry chatter regarding the size of service entrance equipment in relation to actual load, transformers and the like has been heard for at least the last two code cycles. Industry professionals realized that energy-efficient technologies had advanced to a point where load calculations were suspect of being grossly overestimated. Some in the industry claimed load calculation results no longer represented what happens in real-world applications thanks to technologies that use less energy, such as LED lights, fluorescents, high-efficiency transformers and variable frequency drives. Lower energy footprints impact the load calculations used to determine branch circuit size, feeders and everything else associated with power delivery, thus prompting the NEC to make changes that better ensure safety.  
 

The basis of ASHRAE alignment

When many structures are built, ASHRAE requirements adopted by a state or local jurisdiction dictate VA per square foot, and builders may not exceed those requirements. However, CMP2 understood that not every jurisdiction adopts the latest ASHRAE standard. Some states use older ASHRAE requirements, and some jurisdictions don't adopt the requirements at all. This played a factor in the language included in the NEC.

Lower VA per square foot values influence smaller feeder and service sizes, which, if incorrect, could be very expensive to fix after the fact. NFPA members looked at different types of buildings and ASHRAE research data. The task force associated with this effort plotted VA curves for buildings of various sizes. To gain consensus and achieve change, the NEC lowered the VA values somewhat to account for those jurisdictions that do not adopt the latest version of ASHRAE standards or other energy codes. A compromise was reached in using the 2000 version of ASHRAE 90.1 as the uniform reference for VA values.
 

Financial impacts and safety implications

Some industry professionals reported that, when placing an ammeter on a structure’s service conductors, load currents showed a considerable margin between capacity and actual usage. Facilities typically consume less power due to higher-efficiency lighting equipment that’s installed and conservative factors that design engineers may use to ensure future capacity for growth. (Energy-efficient solutions are not required by the Code but are installed because of the energy savings they offer.)

I believe it’s important to include right-sized services in structures that meet design goals driven by customer wants and needs. The Code changes will offer financial relief for electrical infrastructures by foregoing equipment that’s not needed—but the design engineer must always keep a close eye on the needs of the customer. The changes help the design engineer reduce the size of electrical distribution equipment where permitted by the design goals. This could translate into less wire and other related gear. With that, I hope a focus on providing safety technologies for our electrical workers will grow. Funding originally intended for power distribution can be reallocated to safety solutions for branch, feeder and service entrance equipment.
 

A thought on using the Code as a design guide

NEC Article 90 states that the Code should not be used as a design reference. Language in Article 220.12 exemplifies why. As mentioned, there’s an informational note attached to 220.12. It states, “The unit values of Table 220.12 are based on minimum load conditions and 100 percent power factor and may not provide sufficient capacity for the installation contemplated." In essence, this means guidelines may not be sufficient for an installation. So, while the installation may be safe, it may not turn on because there isn’t enough power to serve the load. 

In my opinion, designers must focus on customer wants and create load calculations based on a distribution system’s current and future needs. Many designers look to the Code before creating their designs, but they should do the opposite. I encourage all planners to meet customer wants and needs first and then check their designs against the Code to assure alignment.  

Designers must focus on customer wants and create load calculations based on a distribution system’s current and future needs.

Thomas Domitrovich, vice president, technical sales

What might the future hold?
 

While financial efficiencies and safety improvements were made, the NEC looks to do more to influence load calculations in healthcare environments and commercial structures.

Healthcare

Healthcare representatives believe load calculations are often high because, in an operating room, for example, many receptacles are installed. This makes sense—doctors never want to be without power options when lives hang in the balance. But the additional receptacles cause excessive infrastructure sizing. And practically speaking, many receptacles aren’t used. The NEC is currently researching what, if anything, can be done to improve receptacle load calculations for hospitals and other occupancy types, such as clinics, medical offices and ambulatory care centers.

Commercial structures

A task group launched a research project in collaboration with the NFPA Research Foundation. The team is actively measuring the energy usage on receptacles in a variety of commercial buildings to determine if additional load calculation recommendations are an option. I believe the task group’s report will heavily influence the public input phase for the 2023 code review. 

Better calculations improve efficiency and safety
 

It’s essential to strike a balance when calculating VA. If load calculations are too low, designers may likely plan for and install insufficient equipment, resulting in a situation that’s expensive to fix after the fact. If load calculations are too high, it’s possible to overpay for equipment that’s not needed. I believe Article 220.12’s new load calculations do more to help designers get it right the first time. The changes will help designers save money, which will hopefully inspire their clients to reallocate funds for the safety devices used to reduce maintenance on energized equipment in the field.   

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