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Dec
31

NEC 2020 load calculation changes can make budgets more efficient and increase safety

 by Thomas Domitrovich, P.E., LEED AP, vice president, technical sales at Eaton

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. 

P3 strives to bring you quality relevant industry related news.

See the original full article at: https://www.eaton.com/us/en-us/company/news-insights/for-safetys-sake-blog/load-calculations.html

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Dec
17

The NEC helps the industry understand the safety implications of performance testing

New requirements in NEC Sections 240.67 and 240.87 impact overcurrent protection devices (OCPDs) 1,200 amps and higher or those that can adjust to 1,200 amps and higher. These updates mandate performance testing at the time of installation. Ground-fault protection of equipment (GFPE) at service equipment is an example of an NEC requirement that mandates performance testing to ensure safety technologies are functioning correctly when installed.

With changes including performance testing per manufacturer instructions and recommended test procedures, the electrical industry will soon see significant improvements in power system design and arc flash protection performance. 

  Overview of changes

New text in NEC Sections 240.67 and 240.87 identifies that, when technologies are installed to reduce incident energy, technicians must conduct performance testing at the time of installation. In addition, changes make clear to installers, designers, inspectors and equipment owners that requirements regarding larger OCPDs must respond to lower arcing currents that can occur in equipment.

The arc reduction requirements that began as part of the NEC 2011 code review took a significant step forward in NEC 2020, with changes found in three key areas:

  1. Installation documentation
  2. Safety methodologies
  3. Testing procedures

1) Installation documentation

Documentation requirements changed slightly. A new requirement now mandates proof that installations have arc reduction technologies operating based upon arcing fault current. As always, documentation must be made available to those authorized to design, install, operate or inspect an installation as to the location of all OCPDs impacted. It's critical to understand when these requirements apply and to realize that organizations can always exceed minimum Code requirements by approaching every design with an eye on arc flash hazards.

2) Safety methodologies

When required

Installers, designers and authorities having jurisdiction must understand the entry point of requiring arc reduction technologies as part of 240.67 and 240.87. Circuit breaker requirements of 240.87 establish an arc reduction technology entry point based on circuit breaker ratings and the ability to adjust to 1,200 amps and higher. Fuse applications in Section 240.67 advise that arc reduction technologies are required on applications when a fuse is rated 1,200 amps and above, and only when arcing currents have a clearing time greater than 0.07 seconds. Whether fuse or circuit breaker, an arcing current evaluation must be conducted, documented and made available.

Arcing current

First introduced in 2017, "arcing current" is a term the NEC has yet to define. An informational note was added to NEC 2017, referencing IEEE 1584–2002, IEEE Guide for Performing Arc Flash Hazard Calculations, as a method of providing guidance when determining arcing current.

IEEE 1584-2018 defines arcing current as, "A fault current flowing through an electrical arc plasma." Arcing current is less than the available fault current (short-circuit current) at any point in the power distribution system due to the impedances of plasma and other materials present during an arc flash event. The additional impedance reduces current flow. This value of current will be critical in determining whether or not 240.67 and 240.87 requirements have been met, and in the case of fuses, whether or not an arc reduction technology is required.

Method to reduce clearing time

When an incident energy reduction technology is required, designers and installers may elect to use one of the following means to operate at less than the available arcing current to reduce the clearing time of larger OCPDs:

  • Zone selective interlocking (240.87)
  • Differential relaying (240.67 & 240.87)
  • Energy-reducing maintenance switching with a local status indicator (240.67 & 240.87)
  • Energy-reducing active arc flash mitigation system (240.67 & 240.87)
  • An instantaneous trip setting (temporary adjustment of the instantaneous trip setting to achieve arc energy reduction is not permitted) (240.87)
  • An instantaneous override (240.87)
  • Current-limiting electronically actuated fuses (240.67)

An approved equivalent means is a caveat for the requirements as arc energy reduction technologies continuously improve. The code making panel did not want to limit possibilities for future technologies.

The NEC clarified two issues during the 2020 code review. First, for circuit breakers with an adjustable instantaneous pickup, a "roll-down and back up again" instantaneous trip is not permitted to meet requirements. Field modification of setpoints via dials on the face of circuit breakers is not a good idea for many reasons reviewed and discussed by the code panel. Secondly, these changes help ensure that specified technologies respond to arcing currents provide the protection desired.

3) Testing procedures

Arc energy reduction systems must now be performance tested when installed. Because some of these technologies are complex, requirements mandate that testing be performed only by qualified individuals who follow manufacturer instructions. Qualified individuals must understand that it's possible to damage equipment during tests (e.g., injecting high currents through a fuse can open the fuse, which must then be replaced.) The qualified individual must also understand that some arc reduction technologies do not respond to current alone, demanding a mixture of tools and methods necessary to ensure proper installation.

Qualified individuals must provide a written test record and make that record available to the authority having jurisdiction. The record should be provided to the facility within which it is installed, with files available for future reference.

The rationale for change

Energy reduction requirements evolved with debate and due process of language improvements. While language was first introduced in 2011, it's my opinion that a focus on performance testing wasn't possible until today—code panel members and others in the industry needed time to reach a language consensus. Some argue more should be done, but I believe the overall intent is heading in the right direction.

During the 2020 code review, the code panel and others determined the NEC had to assure technologies are installed and that they are installed correctly at the time of installation, as is done with GFPE. The NEC requires GFPE testing (for equipment protection) when installed, yet did not require performance testing on installed worker-safety technologies.

The code making panel governing GFPE requirements for devices 1,000 amps and above (found in Sections 210, 215, 230 and 240) is the same code panel responsible for Sections 240.67 and 240.87. In some sense, 240.67 and 240.87 requirements are merely a continuation of what began with the GFPE requirements of NEC Section 230.95. Those requirements entered the NEC in 1971, but it wasn't until NEC 1978 that performance requirements at the time of installation were put in place. Section 240.87 followed a similar track. It entered the NEC in 2011; after three code review cycles, the NEC finally began discussing performance testing requirements at the time of installation.

Performance testing

Performance testing is a line item one can't afford to miss when bidding a project. The equipment and performance testing process of GFPE and arc reduction technologies can add significant cost if forgotten. It's essential to address their requirements upfront to maximize project efficiencies.

Here are some things to consider when developing a plan to meet NEC 2020 performance testing requirements:

Combined testing
Combine new performance testing requirements with those of GFPE (230.95 for OCPDs 1,000 amps and above). Projects must have on-site equipment to perform GFPE testing. This equipment can also be used to conduct additional testing for arc reduction.

Solution capabilities

The zones of protection offered by each technology are important to understand; test results may not make sense otherwise. Make sure you follow manufacturer instructions to test solutions correctly.

Current usage

Arcing currents are a function of available short-circuit current and can be quite high. However, technicians do not need to inject high currents to prove that transformers are installed properly and electronic trip units operate correctly. Verifying the entire system with a mix of low primary current injection testing and secondary current injection testing is the safest and most efficient method for success.

Unique conditions

Technologies like arc quenching equipment and active arc flash mitigation systems require more than primary current injection testing to ensure functionality. Light sources and manufacturer testing fixtures may be required.

What might the future hold?

The success of safety to a three-legged stool; one leg is no more important than the others. Today, three critical documents work in unison: the NEC (NFPA 70) provides installation requirements; NFPA 70E provides requirements for safe work practices; NFPA 70B reminds us of the critical role maintenance plays over time. Today the NEC mandates arc reduction technologies and requires assurances that these technologies work at the time of installation. 70E instructs all to leverage these technologies when justified energized work is performed, and 70B dictates periodic testing of these technologies throughout the life of the installation.

As equipment ages, and as devices are removed from and added to power systems, arcing currents change. Designers must remember to update single-line diagrams and systems analysis studies and make sure the technologies effectively provide arc energy reduction well after installation. In short, proper maintenance is vital.

P3 strives to bring you quality relevant industry related news.

See the original full article at: https://www.eaton.com/us/en-us/company/news-insights/for-safetys-sake-blog/performance-testing.html

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104 Hits
Dec
12

Arc flash: are you prepared?

Arc flash safety and NFPA 70E, OSHA's OSH Act -  is your facility in compliance?

Have you taken the proper steps to help protect your facility and its employees against the dangers of arc flash? Find out now. Simply answer a brief set of questions with Eaton's Reset Safety tool, and they will send you a customized preparedness profile to help you identify ways to reset safety in your facility. 

P3 strives to bring you quality relevant industry related news.

See the original full article at: https://www.eaton.com/us/en-us/company/news-insights/reset-safety-arc-flash.html

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173 Hits
Dec
02

CEDIA Releases Power Quality White Paper

Paper helps break down topics of electrical noise and power anomalies

The Custom Electronic Design & Installation Association (CEDIA) recently released The Quality of Power, a white paper that explores conditions and causes of electrical problems, and the solutions to deliver a better quality of power.

"There is no denying that technology is more a part of our daily lives than it has ever been before. The digital native generation does not know a world without the internet. With this demand for access to technology comes another sometimes overlooked need – the need for power that is free from transients, interruptions and noise," says Walt Zerbe, senior director of technology and standards. "CEDIA's new white paper explores why it is important to have quality power and how integrators can deliver better quality power to their clients."

The white paper helps break down the complex topics of electrical noise and power anomalies and what can be done to mitigate their effects.

CEDIA members can download a complimentary copy of The Quality of Power through the CEDIA Resource Catalogue. It is available to non-members for $99. 

P3 strives to bring you quality relevant industry related news.

See the original full article at: https://www.ecmweb.com/power-quality-reliability/cedia-releases-power-quality-white-paper?NL=ECM-06&Issue=ECM-06_20191127_ECM-06_866&sfvc4enews=42&cl=article_2_b&utm_rid=CPG04000000918978&utm_campaign=30075&utm_medium=email&elq2=a0d36a15a47e4727a68bbf5a8e0ea353&oly_enc_id=6901B0580289B1P

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