Gasfitter Class B 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.

📖Class B Scope of Work

Class B: low-pressure residential and light commercial natural gas systems
Typical Class B work: furnaces, water heaters, fireplaces, ranges, dryers, BBQ connections
NOT Class B: high-pressure systems, propane storage, industrial processes, underground distribution
Class B Gasfitter must work under Class A supervision on any work outside Class B scope

📖Residential Furnaces

Induced draft (Category III): powered blower draws flue gases through heat exchanger
Sealed combustion (Category IV): draws outside air directly; PVC vent; most efficient
AFUE: Annual Fuel Utilization Efficiency — minimum 95% AFUE for new installs in many provinces
High-efficiency condensing: produces condensate — needs drain; vent must be Category IV

🔥Water Heaters

Storage tank: most common; 40–60 gallon; 7" WC operating pressure at burner
Tankless (on-demand): condensing or non-condensing; requires adequate gas supply and venting
Temperature setting: maximum 49°C (120°F) residential — anti-scald requirement
Temperature and pressure (T&P) relief valve: tested annually; discharge pipe to floor

📖Gas Fireplaces

Direct-vent: sealed combustion; combustion air from outside; most common new installation
B-vent: draws room air for combustion; vents vertically through roof
Decorative (ventless): no vent — prohibited in bedrooms, bathrooms; CO risk; many provinces ban them
Termination clearances: vent terminations must meet B149.1 clearance requirements from windows, doors

🦺Carbon Monoxide Safety

CO alarm required within 5 m of sleeping areas (most provincial codes)
Symptoms at low levels: headache, dizziness, nausea — often confused with flu
CO sources: incomplete combustion, cracked heat exchanger, blocked vent, back-drafting
If CO alarm sounds: evacuate, call 911, do not re-enter until authorities clear building

📖Testing & Commissioning

Pressure test before concealing: 15 kPa (60" WC) for 15 minutes with no pressure drop
Leak test all joints with soap solution after pressure test and before lighting
Combustion analysis: verify CO₂ %, O₂ %, CO ppm, and stack temperature after commissioning
Appliance check: verify proper ignition, flame appearance, and shut-off on thermostat call end

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 Categories — Residential

Category I (B-vent): natural draft, non-positive pressure; double-wall Type B; ≤140°F flue temp
Category III: positive pressure, non-condensing; AL29-4C stainless single-wall rigid vent
Category IV: positive pressure, condensing; Schedule 40 PVC or polypropylene; condensate drain
Common vent: two Category I appliances on one vent — B149.1 limits and sizing tables apply

📖Vent Termination Clearances (B149.1)

Forced vent / direct vent terminal: 30 cm (12") from openings into building
Above grade: 30 cm minimum from finished grade in normal snowfall areas
No termination under deck or inside enclosed porch — CO re-entry risk
Gas meter: 1 m (3 ft) clearance from vent termination (some exceptions for Category IV)

📖Thermostat & Controls

24V thermostat: standard for most residential furnaces; R, G, W (heat), Y (cooling) terminals
Programmable/smart thermostats: same wiring; require C (common) wire for powered models
High-limit control: bimetal or electronic; opens at 85–90°C — shuts off burner on overheating
Roll-out switch: manual reset; activates if flames roll out of heat exchanger — check for cause

💡Equipment Sizing Basics

Heat loss calculation (Manual J equivalent): determines required furnace output in BTU/h
Oversizing: reduces efficiency, increases short-cycling — maximum 25% oversize acceptable
Water heater sizing: first-hour rating (FHR) matched to peak household demand
Gas supply: ensure adequate line capacity (BTU/h) — size pipe per B149.1 tables

📖AFUE Ratings

AFUE: percentage of fuel converted to heat delivered to home; 95% = 5% losses up stack
Standard efficiency: 80% AFUE — some exhaust heat escapes; Category I vent
High efficiency: 90–98% AFUE — condensing; Category IV PVC vent; lower stack temp
National Energy Code for Buildings (NECB): minimum AFUE requirements vary by climate zone

📖Provincial Licensing Requirements

Each province has its own gas fitter licensing authority (TSSA in ON, Safety Codes Council in AB)
Class B written exam + practical assessment + documented apprentice hours required
Red Seal Interprovincial: passes written Red Seal exam — recognized Canada-wide
Annual continuing education: many provinces require minimum CEU hours for renewal