Gasfitter Class A Study Guide — Year 1

Year 1 Exam Topics

Study each topic below — these are the core knowledge areas tested in Year 1. Build a solid foundation here before advancing to Year 2 material.

📋CSA B149.1 — The Code

Natural Gas and Propane Installation Code — the primary standard for ALL gas work in Canada
Adopted by provinces with local amendments; always check provincial authority's version
Permits: required for new installations, alterations, additions — not for routine maintenance
Inspector approval required before concealing piping or connecting new appliances

💡Gas Pressure Basics

Natural gas distribution: medium pressure (7–35 kPa) in street mains
Service regulator steps down to low pressure: 1.75 kPa (7" WC) for residential
High-pressure systems: above 35 kPa — Class A scope; requires engineer involvement
Propane: higher energy density; storage tank pressure varies with temperature (~830 kPa at 20°C)

💡Combustion Theory

Complete combustion: gas + oxygen → CO₂ + H₂O + heat (no CO produced)
Stoichiometric ratio for natural gas: ~10:1 air-to-gas by volume
CO (carbon monoxide): colourless, odourless, toxic — produced by incomplete combustion
CO limit: ASHRAE recommends ambient CO under 9 ppm; combustion products <200 ppm CO

🔧Piping Materials & Joints

Black steel pipe: standard for gas — threaded or welded joints; no galvanized in gas systems
CSST (corrugated stainless steel tubing): flexible; requires bonding per B149.1
Copper: permitted for LP gas in some jurisdictions — not for natural gas (mercury reacts)
Polyethylene (PE): underground only; fusion welded joints; yellow colour

📖Testing — Leak & Pressure

Leak test: apply soap solution (or electronic detector) at every joint — bubbles = leak
Pressure test (new pipe): test at 1.5× MAOP, minimum 10 min, with manometer
Low-pressure test: 15 kPa (60" WC) for 15 minutes — no pressure drop allowed
Medium/high-pressure: 50 kPa (7.25 psi) test pressure; 30-minute hold required

🦺Safety Devices & Controls

Thermocouple/thermopile: generates voltage from pilot flame — holds gas valve open
High-limit control: shuts off burner if temperature exceeds safe limit
Pressure relief valve: protects vessel from excess pressure — never plug or cap
Excess flow valve (EFV): shuts off flow if service line ruptures — installed at meter

Study each topic below — these are the core knowledge areas tested in Year 1. Build a solid foundation here before advancing to Year 2 material.

📖Venting Systems

Category I: non-positive pressure, ≥140°F flue gas — Type B vent; metal double-wall
Category II: non-positive, condensing — special materials; rare in Canada
Category III: positive pressure, non-condensing — Type B or AL29-4C stainless
Category IV: positive pressure, condensing — Schedule 40 PVC or polypropylene pipe

📐Pipe Sizing — B149.1 Tables

Determine total BTU/h demand for all connected appliances on each segment
Longest run method: size all pipe based on total developed length to farthest appliance
Pressure drop allowed: 0.5" WC (125 Pa) max for low-pressure residential distribution
B149.1 Appendix A: pipe sizing tables for natural gas and propane; select pipe by length and BTU

📖Commercial Appliances

Commercial cooking: rooftop exhaust hoods required — Type I for grease-producing equipment
Unit heaters: suspended; requires combustion air and vent per B149.1 Clause 8
Infrared tube heaters: radiant; positive pressure vented; special termination required
Boilers >400 MBH: require combustion air engineering calculation per B149.1

📖Combustion Air Requirements

Confined space: additional combustion air openings required (1 sq in per 1,000 BTU/h)
Unconfined space: natural infiltration supplies combustion air in large/leaky buildings only
Direct vent / sealed combustion: draws 100% combustion air from outside — no room air needed
Make-up air: required if exhaust fans depressurize building — B149.1 Table 8.2

📖Gas Meters & Regulators

Diaphragm meter: most common; measures gas volume by alternating chamber filling/emptying
Service regulator: reduces street pressure to appliance pressure; has vent limiting orifice
Two-stage LP: first stage (high pressure) → second stage (low pressure) at appliance
Regulator failure mode: should fail closed (no gas) not open (unregulated pressure)

📖Inspector Requirements

Technical Standards and Safety Authority (TSSA) in Ontario; equivalent in each province
Class A Gasfitter: may install and maintain all gas systems regardless of pressure or size
Class A scope: includes industrial, commercial, high-pressure pipelines, and storage systems
Inspection documents: permit, approved drawings, test results retained for minimum 3 years