Hazardous Locations and Special Installations

Hazardous Locations and Special Installations

Chapter Introduction

This chapter covers the regulatory requirements and technical principles relating to hazardous locations and special installations, as defined by the Canadian Electrical Code, Part I (CE Code), Chapter V and related CSA standards. For the Red Seal exam, you must master area classification, equipment selection, installation methods, distance calculations, and special requirements for systems such as generators, storage batteries, and photovoltaic installations. This chapter prepares you to identify, apply, and justify the applicable rules in a practical context.

Classification of Hazardous Locations

Fundamental Definitions

A hazardous location is a place where dangerous concentrations of flammable gases, vapours, dusts, or fibres may exist. The CE Code, Chapter V, Section 18, divides these locations into zones and divisions according to the probability and duration of the presence of the explosive atmosphere.

The following table summarizes the correspondence between zones and divisions for gases and vapours:

Gas and Dust Groups

Gases and vapours are classified into groups according to their ignition behaviour:

For dusts, the groups are Group IIIA (flyings), Group IIIB (non-conductive dusts), and Group IIIC (conductive dusts). Equipment selection must account for the specific group: equipment certified for Group IIA is not suitable for Group IIC.

Ignition Temperatures and Temperature Classes

Each gas or dust has an auto-ignition temperature (AIT). Electrical equipment must never have a surface temperature exceeding 80% of the AIT of the gas or dust present. The CE Code defines six temperature classes (T1 to T6):

Example: For hydrogen (AIT ≈ 560 °C), Class T1 is suitable. For carbon disulphide (AIT ≈ 90 °C), only Class T6 is acceptable.

Electrical Equipment for Hazardous Locations

Types of Protection

The CE Code recognizes several types of protection for equipment installed in hazardous areas:

The following table compares the types of protection:

Equipment Marking

All certified equipment must bear a marking indicating:

Example of marking: Ex d IIC T6 means explosion-proof, Group IIC, maximum surface temperature 85 °C.

Rule 18-100 and Subsequent Rules

Rule 18-100 requires that all equipment installed in a hazardous location be certified for the intended use. Rules 18-102 to 18-108 deal with specific installations: wiring, fittings, cable glands, seals, etc.

Common trap to avoid: Do not confuse the sealing requirements for Zones 1 and 2. In Zone 2, seals are required only if the enclosure contains contacts capable of producing arcs.

Special Installations: Generators and Motors

Standby and Replacement Generators

Generators installed in buildings must comply with Rule 26-200 of the CE Code. Key requirements include:

Sizing calculation: For a 150 kVA, 600 V three-phase generator, the rated current is:

I = P / (√3 × U) = 150,000 / (1.732 × 600) ≈ 144 A

The circuit breaker must be rated at 150 A or 175 A depending on commercial availability, in accordance with Rule 14-104 (maximum setting of 125% of rated current).

Motors in Hazardous Locations

Motors installed in Zones 1 or 2 must be certified for the location. Explosion-proof motors (Ex d) are common for pumps and fans. Requirements include:

Example: 25 hp motor, 600 V, full-load current of 24 A. The conductor must be sized for 24 × 1.25 = 30 A. A #10 AWG cable (35 A at 75 °C) is suitable.

Photovoltaic (PV) Installations

Requirements of Rule 64-200

Photovoltaic installations are covered by Section 64 of the CE Code. Key rules include:

Sizing calculation: For a module with Isc = 9.5 A, the sizing current is:

I = 9.5 × 1.25 = 11.875 A

The conductor must be sized for at least 11.875 A, and the circuit breaker for 15 A (standard value).

Grounding of PV Systems

Rule 64-210 requires grounding of module frames and metal supports. The grounding conductor must be sized according to Rule 10-114, based on the rated current of the protected circuit.

Common trap to avoid: PV modules with aluminium frames require contact washers or star washers to ensure a reliable electrical connection, because aluminium naturally oxidizes.

Storage Batteries

Rule 26-500 and Subsequent Rules

Storage battery installations are covered by Rule 26-500. Requirements include:

Conductor Sizing

The maximum charging current is used to size conductors. For a 48 V battery bank with a 100 A charger, conductors must be sized for 100 × 1.25 = 125 A. A #1/0 AWG cable (150 A at 75 °C) is suitable.

Rule 26-508: Batteries must be equipped with an accessible and identifiable disconnecting means.

Grounding and Bonding Systems

Rules 10-200 and 10-300

Rule 10-200 requires grounding of all electrical systems of 50 V or more. Rule 10-300 deals with bonding of metal masses.

Ground resistance calculation: The resistance of a grounding electrode must be less than 25 Ω (Rule 10-400). For industrial installations, a resistance of less than 5 Ω is recommended.

Example: A 3 m long, 16 mm diameter electrode driven into soil with a resistivity of 100 Ω·m:

R = ρ / (2πL) × ln(4L / r) = 100 / (2π × 3) × ln(12 / 0.008) ≈ 5.3 Ω

This value is acceptable according to the CE Code.

Bonding in Hazardous Locations

In hazardous locations, Rule 18-116 requires bonding of all metal masses, including conduits, enclosures, and structures. The bonding conductor must be copper, at least 4 mm².

Temporary and Construction Site Installations

Rule 76-100

Temporary installations (construction sites) are covered by Section 76. Requirements include:

Common trap to avoid: GFCIs for temporary installations must be tested before each use and at least once per week.

Comparative Tables of Requirements

Comparison of Zones and Divisions

Conductor Sizing

Common Traps to Avoid

Summary

Review Questions

Answers to Review Questions