CSA C22.2 No. 56-17: Flexible Metal Conduit and Liquid‑Tight Flexible Metal Conduit

CSA C22.2 No. 56‑17 is the Canadian national standard governing the construction, performance, and testing of flexible metal conduit (FMC) and liquid‑tight flexible metal conduit (LFMC). Published under the Canadian Electrical Code (CE Code) Part II umbrella, this standard ensures that flexible conduit systems used in electrical installations meet rigorous safety and durability requirements. The 2017 edition supersedes previous versions and incorporates harmonized provisions with corresponding UL and IEC standards where applicable.

This article provides a technical overview of the standard’s scope, key requirements, implementation guidance, and compliance considerations for manufacturers, specifiers, and installers.

Scope

CSA C22.2 No. 56‑17 applies to flexible metal conduit and liquid‑tight flexible metal conduit intended for use as an enclosed wiring method for the installation of electrical conductors in accordance with the Canadian Electrical Code, Part I (CSA C22.1). The standard covers:

• Round, helically wound, interlocked or corrugated flexible metal conduit (FMC) made of steel or aluminum.
• Liquid‑tight flexible metal conduit (LFMC) constructed with a flexible metal core and a continuous, liquid‑tight polymeric outer jacket.
• Conduit sizes from 3/8 inch (12 mm) up to 4 inches (103 mm) trade size, and metric equivalents (12–103 mm).
• Fittings, connectors, and couplings that are intended to be used with FMC and LFMC (if covered under the same product certification).

The standard does not apply to non‑metallic flexible conduit, which is covered by separate standards (e.g., CSA C22.2 No. 227.2). LFMC products covered by this standard are intended for use in damp, wet, or corrosive locations, including outdoor installations and areas subject to occasional liquid splash or submersion.

Technical Requirements

Construction and Dimensions

Mechanical Tests

• Bend test: Conduit must withstand bending around a mandrel at the specified radius without fracture or permanent deformation that reduces internal diameter by more than 40%.
• Impact test: LFMC samples are subjected to a 1.8 kg (4 lb) steel ball dropped from 0.3 m (12 in). No cracking or leakage of the jacket is permitted.
• Crush test: Conduit is compressed between flat platens to 50% of its original diameter. After release, the internal diameter must be at least 80% of the original nominal value.
• Flexing and endurance: For LFMC, a cyclic flexing test of 5,000 cycles with a specified torque is performed to verify the jacket and core integrity.

Liquid‑Tightness

For LFMC, the standard requires a water leakage test: a 300 mm (12 in) sample, with an open end, is immersed in 1 m (3.3 ft) of water while the other end is sealed. No water ingress into the interior is permitted after 24 hours. Additionally, a hydraulic pressure test ensures the jacket does not leak when subjected to 35 kPa (5 psi) internal air pressure.

Electrical Continuity

Conduit must provide reliable electrical continuity for bonding. The standard sets a maximum dc resistance for a 1 m (3.28 ft) length of conduit at 20 °C. For example, a ½″ (16 mm) FMC must have a resistance no greater than 0.005 Ω. LFMC, which includes a non‑conductive jacket, must still meet the same resistance requirement via the metal core.

Implementation Highlights

Marking

Each length of conduit must be legibly and durably marked at intervals not exceeding 1.2 m (4 ft) with:

• The manufacturer’s name or trademark.
• The trade size in inches or metric.
• The type designation: “FMC” or “LFMC”.
• The standard reference: “CSA C22.2 No. 56” or the appropriate CSA certification mark.
• For LFMC, the temperature rating and suitability for wet locations may be indicated (e.g., “Wet Location”, “Watertight”).

Installation Guidelines

• FMC and LFMC must be supported and secured at intervals not exceeding 1.5 m (5 ft) unless used with approved fittings that provide support.
• Where used as an equipment grounding conductor (bonding jumper), the conduit must meet the resistance requirements and the installation must comply with Section 10 of the CE Code.
• In hazardous locations, only LFMC listed for such environments may be used.
• Conduit length within motor terminal boxes or similar enclosures should not exceed 600 mm (2 ft) unless specifically permitted.

Compliance Notes

Certification Bodies

In Canada, CSA C22.2 No. 56‑17 is a mandatory standard under provincial electrical safety regulations. Products may be certified by any accredited certification body (e.g., CSA, UL, Intertek, TÜV SÜD). The mark indicates compliance with the standard and acceptance by provincial authorities.

Periodic Tests

Manufacturers are required to conduct follow‑up inspections and periodic testing to ensure ongoing conformity. The re‑test intervals for factory testing typically include:

• Bend test – every 2 years.
• Impact and crush tests – annually.
• Water leakage test (LFMC) – every 3 years.

Changes in the 2017 Edition

The 2017 edition introduced clarifications on:

• Test sample conditioning (temperature and humidity).
• Updated strip force test for LFMC jackets (minimum 222 N).
• New requirements for markings on metric‑sized conduit.
• Harmonization of bend radii with UL 360.

Specifiers and distributors should verify that stock items carry the certification mark and the correct year of the standard (or no revision year, indicating latest).

FAQs

CSA C22.2 No. 56‑17 (2017) remains the benchmark for flexible metal conduit safety and performance in Canada. Understanding its technical provisions is essential for anyone involved in specifying, manufacturing, or inspecting electrical conduit systems.