Pre-engineered Solutions Take Guesswork Out of the Equation
Steve Maurer, IME
In any building or facility, the power system is the backbone of operations. Without power, you’re literally left standing in the dark.
And while mother nature can be a beast, creating power outages that can’t always be planned for, often the culprit is somewhere in a complex electrical system. A short in one location could conceivably have a domino effect for the rest of the facility.
In simple systems, like homes or similar situations, this may not be much of a problem. Rarely have I ever seen an electrical short in a bathroom, for example, take down the entire domicile. I guess it could happen but the consequences are more of a nuisance than a real catastrophe.
In a complex power infrastructure, a fault in one remote location could cause the entire house of cards to go tumbling down around you. And in some cases, that could be physically, not figuratively.
To prevent total failure caused by one isolated fault, the electrical system must be designed using the principles of selective coordination. This will keep one faulted circuit from affecting the branches that feed it.
And while mother nature can be a beast, creating power outages that can’t always be planned for, often the culprit is somewhere in a complex electrical system. A short in one location could conceivably have a domino effect for the rest of the facility.
In simple systems, like homes or similar situations, this may not be much of a problem. Rarely have I ever seen an electrical short in a bathroom, for example, take down the entire domicile. I guess it could happen but the consequences are more of a nuisance than a real catastrophe.
In a complex power infrastructure, a fault in one remote location could cause the entire house of cards to go tumbling down around you. And in some cases, that could be physically, not figuratively.
To prevent total failure caused by one isolated fault, the electrical system must be designed using the principles of selective coordination. This will keep one faulted circuit from affecting the branches that feed it.
According to Article 100 of the 2020 NEC®, selective coordination is defined as:
Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.
While there may be some instances where selective coordination isn’t required nor a necessity, there are some circuits and facilities that must adhere to various Code standards in order to be compliant. The NEC® calls out the definitions and requirements for selective coordination. Additionally, performance requirements for selectively coordinated systems are also set forth in NFPA 99 – Health Care Facilities Code and NFPA 110 – Standard for Emergency and Standby Power Systems.
Here are some of the most commonly referenced provisions in the NEC® for selective coordination, presented by Article, application, and requirement:
- 517 – healthcare facilities – 517.26
- 620 – elevators and escalators – 620.62
- 645 – IT/data systems – 645.27
- 695 – fire pumps – 695.3(C)(3)
- 700 – emergency systems – 700.10(B)(5)(b)(ii); 700.32
- 701 – legally required standby systems – 701.32
- 708 – critical operations power systems – 708.54
Often, electrical systems and parts manufacturers have in-house staff that can assist in designing the power systems and specifying the correct parts.
Other companies have pre-engineered component systems to help take the guesswork out of system design. Pre-engineered panels and switches make procurement and code compliance easier. Of course, these are specifically designed for non-residential construction.
These pre-engineered systems are designed and built to meet NEC® requirements for those areas needing selective coordination protection.
For some specialized uses such as elevator circuits, data processing rooms, and building emergency systems, you may need a selective coordination panel with shut trip capabilities. Some will have Class J time-delay fuses for coordination. The shunt trip capability allows it to meet the ANSI/ASME standard requiring power to be automatically disconnected before the fire safety system turns on the water for fire suppression.
These will come pre-wired for easier installation and should be lockable. Additionally, you can often get a range of options, from control power transformers to pilot lights and mechanical interlocks.
When designing and building a selective coordination system for your application, don’t guess at what you’ll need and how you’ll assemble it.
Pre-engineered solutions are available to keep you in compliance … and help you sleep at night.
Other companies have pre-engineered component systems to help take the guesswork out of system design. Pre-engineered panels and switches make procurement and code compliance easier. Of course, these are specifically designed for non-residential construction.
These pre-engineered systems are designed and built to meet NEC® requirements for those areas needing selective coordination protection.
For some specialized uses such as elevator circuits, data processing rooms, and building emergency systems, you may need a selective coordination panel with shut trip capabilities. Some will have Class J time-delay fuses for coordination. The shunt trip capability allows it to meet the ANSI/ASME standard requiring power to be automatically disconnected before the fire safety system turns on the water for fire suppression.
These will come pre-wired for easier installation and should be lockable. Additionally, you can often get a range of options, from control power transformers to pilot lights and mechanical interlocks.
When designing and building a selective coordination system for your application, don’t guess at what you’ll need and how you’ll assemble it.
Pre-engineered solutions are available to keep you in compliance … and help you sleep at night.
Photo courtesy of Littelfuse