Working spaces for 600 V equipments installations (NFPA 70)

National Electrical Code (NFPA 70) – Working Spaces for 600 V Electrical Equipment

In electrical installations, providing adequate working space around electrical equipment is not just good engineering practice—it is a mandatory safety requirement under the National Electrical Code (NEC/NFPA 70). These provisions are designed to ensure safe operation, inspection, and maintenance of equipment rated at 600 Volts, nominal, or less.

This article explains the key working space requirements, exceptions, and clearances mandated by NEC for low-voltage electrical systems.

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1. General Requirement for Working Space

• Sufficient access and working space must be provided for safe operation, inspection, and maintenance.

• Spaces must comply with NEC specifications regarding depth, width, and height.

• No storage or obstruction is allowed in the designated working space.

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2. Working Space Depth Requirements

(a) Minimum Depth

The minimum clear working distance depends on system voltage and conditions outlined in NEC Table 110.26(A)(1). Distances are measured from exposed live parts, the enclosure, or the opening if the parts are enclosed.

(b) Dead-Front Assemblies

• Applies to switchboards, panelboards, and motor control centers (MCCs) where all live parts are accessible from the front only.

• No working space is required at the back, unless rear access is necessary.

• If rear access is required (non-electrical parts), at least 762 mm (30 in.) clearance must be provided.

(c) Low-Voltage Exception

For exposed live parts between 30 V RMS and 60 V RMS, working space clearance may be reduced—but only with special permission from the authority having jurisdiction (AHJ).

(d) Existing Buildings

When replacing equipment in older buildings:

• NEC allows reduced clearance under Condition 2 of Table 110.26(A)(1).

• Only permitted where strict maintenance procedures are in place (e.g., ensuring opposite equipment doors cannot be opened simultaneously).

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3. Working Space Width

• Clearance width = the width of the equipment or 762 mm (30 in.), whichever is greater.

• Must allow at least a 90° opening of doors or hinged panels.

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4. Working Space Height

• Must extend from the floor or grade up to 2.0 m (6.5 ft) or the equipment height, whichever is greater.

• Other equipment may project max 150 mm (6 in.) into this space.

Exceptions:

1. Residential service equipment/panelboards ≤ 200 A may have less than 2.0 m height.

2. Meters in sockets may project beyond equipment limits.

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5. Clear Spaces (No Storage)

• NEC strictly prohibits storage in required working space.

• When normally enclosed live parts are exposed for servicing, temporary guarding must be provided if the space is in a passageway or open area.

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6. Entrance and Egress Requirements

(a) Minimum Requirement

• At least one entrance of sufficient size must be provided.

(b) Large Equipment (≥1200 A, >1.8 m wide)

• Requires two entrances (each ≥610 mm wide and ≥2.0 m high) at opposite ends of working space.

• A single entrance is allowed only if:

  • Unobstructed egress exists, OR

  • Working space depth is double the NEC minimum requirement.

(c) Personnel Doors

For equipment >1200 A within 25 ft of working space, doors must:

• Open outward (in direction of egress)

• Be equipped with panic bars/pressure plates for quick escape.

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7. Illumination

• Adequate lighting must be provided for all working spaces around switchboards, MCCs, and panelboards.

• Lighting must not be controlled by automatic means only.

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8. Dedicated Equipment Space

(a) Indoor Installations

• Dedicated space = width and depth of equipment, extending 1.8 m (6 ft) above equipment or to structural ceiling.

• No foreign systems (piping, ducts, leak protection devices) allowed in this space.

Exceptions:

• Suspended ceilings with removable panels are permitted.

• Sprinkler protection is allowed if installed properly.

(b) Outdoor Installations

• Equipment must be in suitable enclosures.

• Must be protected against accidental contact, vehicular traffic, or liquid leakage.

• Clearance zone must remain unobstructed.

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9. Locked Electrical Rooms

• Locked rooms or enclosures housing electrical equipment are considered accessible to qualified persons.

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Key Takeaways

• NEC mandates strict depth, width, and height clearances for safe working spaces.

• No storage is permitted in working zones.

• Large equipment requires special egress provisions (panic bars, double exits, or extra depth).

• Indoor and outdoor installations have dedicated clearance requirements.

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✅ Disclaimer: This article provides a simplified explanation of NEC/NFPA 70 requirements for working spaces. Always refer to the latest NEC code and consult the Authority Having Jurisdiction (AHJ) for final compliance.

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