Electrical equipment working clearances to help prevent a flashy end

Posted in: Energy, Water


electrical-overload-300x225pxWhat are best practices for designing electrical working spaces, so that you avoid catastrophe? Let me share the basics with you.

Electrical equipment is divided into two categories. Electrical working space and dedicated electrical equipment space. Electrical working space covers equipment that will be serviced, maintained or operated while energized. Dedicated electrical equipment space is equipment not requiring servicing, maintenance or operation while energized.

There are three main components to electrical working spaces – depth, width and height. Together these three components provide adequate working clearances for maintenance, staff, qualified personnel and operators around electrical equipment. During design and installation these components must be followed as indicated in NEC 110.26(A) Working Space (1), (2) and (3).

The Depth

The depth of working space is the distance from the front of electrical equipment. If there isn’t an enclosure around the equipment then the distance is measured from the exposed live parts. NEC Table 110.26(A)(1) indicates the working depth requirements under three conditions at 0-150V and 151-600V nominal voltage to ground.

Condition 1 – This is the distance between electrical exposed live parts or enclosure dead front to an insulated wall. The working clearances for this condition are a minimum distance of three feet for both 0-150V and 151-600V nominal voltage to ground.

Condition 2 – This considers the electrical exposed live parts or enclosure dead front to a grounded wall such as concrete or brick. In most cases the walls is considered to be grounded, and if a little extra space is provided no one will complain. The working clearances for 0-150V nominal voltage to ground remains at three feet, but 151-600V nominal voltage to ground requires a 3½ feet minimum of working space.

Condition 3 – This occurs when the electrical equipment faces each other. This means there is exposed live parts or enclosure dead front on both sides with the walking path or the working space between. The working clearances for this condition requires 0-150V nominal voltage to ground to be a minimum of three feet. Voltages 151-600 nominal voltage to ground requires a minimum distance of four feet of working space.

The Width

The width of electrical working space is a minimum of 30 inches and never smaller. If the equipment is larger than 30 inches, then the width of the working space will be the width of the electrical equipment minimum. If the equipment has hinged doors or is able to swing open, then you must provide sufficient space for the door to open a minimum of 90 degrees.

The Height

The height of the working space is from grade level, floor or platform with a minimum height of 6½ feet. If the electrical equipment is taller than 6½ feet, then the minimum working height is the height of the electrical equipment. The working space can be encroached on for a maximum of six inches with associated equipment such as a raceway or wireway. The exception to Number 2 of NEC 110.26(A)(3) indicates that meters must be permitted to extend beyond the six inches.

In addition to the working space requirements from NEC 110.26(A) (1), (2) and (3) additional codes are required to follow for:

  • Clear spaces
  • Entrance and egress path
  • Illumination
  • Dedicated equipment space
  • Locked electrical equipment rooms or enclosures

Remember that electrical working clearances are important and required per the NEC code and are in place to help protect and provide a safe working environment.

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brandon-winchell-258x258pxABOUT THE AUTHOR

Brandon Winchell, P.E., is a registered electrical engineer who has created power, instrumentation and control designs for water and wastewater facilities, as well as dams and flood control systems. His skills include security and automation. On weekends you can find Brandon out on his motorcycle, creating amazing dishes from scratch (be sure to ask for his chili recipe) or working on projects around the house.

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