PGDB Certifying Gasfitter cheat sheet

In Canada the CSA B149.1 Natural Gas and Propane Installation Code governs installation; B149.2 covers propane storage and handling, and B149.3 covers appliance and equipment approval.

The Gas Protection Branch (municipal/ provincial authority) issues gasfitter licences and permits; work must not proceed without the required permit and inspection notice.

Code requirements are minimums; manufacturer's certified installation instructions always take precedence where they are more restrictive.

Clearances to combustible material are measured from the appliance or vent surface to the combustible surface; reduced clearances require an approved listed clearance shield or protection per the certification.

A field approval (special inspection) is required for unlisted appliances or equipment; the authority having jurisdiction must approve before installation.

B149.1 requires that alterations, additions, and repairs be performed by a certified gasfitter holding the appropriate class, and that the installation be left in a safe condition.

Definitions matter on exams: 'approved' means acceptable to the authority having jurisdiction; 'listed' means certified by a recognized testing agency (e.g., CSA, ULC, Intertek, UL).

Propane cylinder exchange and refilling are regulated separately; a gasfitter may only perform work within the scope of their certificate class (e.g., Class A, B, or C).

Complete combustion of methane: CH4 + 2O2 → CO2 + 2H2O; each volume of methane requires two volumes of oxygen (about 9.5 volumes of air).

Propane combustion: C3H8 + 5O2 → 3CO2 + 4H2O; stoichiometric air requirement is approximately 23.8 volumes of air per volume of propane.

Natural gas heating value is roughly 1,000–1,050 BTU/ft³ (about 37 MJ/m³); propane vapour is about 2,500 BTU/ft³ (about 93 MJ/m³); butane about 3,200 BTU/ft³.

Specific gravity: natural gas ≈ 0.60 (lighter than air, rises and vents at high points); propane vapour ≈ 1.52 (heavier than air, settles in low areas, pits, and basements).

Flammable limits in air: natural gas ≈ 4–15% by volume; propane ≈ 2.1–9.5% by volume. Below the LFL the mixture is too lean, above the UFL too rich, to ignite.

Propane liquid expands roughly 1.5% per 10°F (about 1.5% per 5.5°C); cylinders must never be filled beyond 80% liquid capacity to allow for expansion.

Ignition temperature: natural gas ≈ 1,100°F (593°C); propane ≈ 920–1,020°F (about 493–550°C).

Excess air (O2 in flue gas) indicates dilution; CO in flue gas indicates incomplete combustion. CO2 max for natural gas is about 11.7–12%; for propane about 13.8%.

Category I appliances are non-condensing, negative draft, and vent with B-vent; Category III are positive pressure non-condensing; Category IV are condensing positive pressure (use listed PVC/CPVC/stainless per manufacturer).

Natural draft (B-vent) systems rely on a warm flue and adequate draft; a blocked flue or downdraft spills products of combustion into the space, creating CO hazard.

Combustion air: the 'tight construction' rule requires outdoor air; conventional opening sizing uses 1 in² free area per 1,000 BTU/h input for two permanent openings (or per code table).

For a confined space, two openings (high and low) are required, each sized to the total input; a louvered grille reduces free area and must be compensated (metal louvers ≈ 75% free area, wood ≈ 25%).

Vent connectors must slope upward toward the chimney at minimum 1/4 in per foot (about 20 mm/m) for natural draft appliances, and be as short and direct as possible.

A vent termination must be located away from windows, doors, and air intakes per code clearances (typically 3 ft/1 m horizontally from an operable window or intake, and above roof snow line).

Side-wall power venters must be listed for the appliance and installed per manufacturer clearances; condensate from Category IV vents must be drained and neutralized where required.

Draft hood/spill switch: a blocked flue can cause spillage at the draft hood; a spill switch (spillage switch) shuts off the burner on detected spillage.

Sizing methods: longest-length (longest run) method and branch-length method; use the total connected load and the longest equivalent length to select pipe size from code tables.

Equivalent length adds fittings: a 90° elbow ≈ 5 ft, a 45° elbow ≈ 2.5 ft, a tee (flow through branch) ≈ 10 ft, and a gate valve ≈ 1 ft of straight pipe (values per code tables).

Natural gas pressure drop allowance for low-pressure systems is typically 0.5 in w.c. from meter to appliance; propane systems use 0.5 in w.c. for 11 in w.c. supply.

Minimum size limits: no gas piping smaller than 1/2 in nominal; appliance connectors must be listed and not exceed 6 ft (1.8 m) for movable appliances, and must not pass through walls or floors.

Pressure test: new natural gas piping is tested with air or inert gas at not less than 1.5 times the maximum working pressure, minimum 10 psig (or per code) for a specified duration, with no pressure drop.

Leak testing must never be done with a flame; use soap solution, a combustible gas detector, or a manometer. A pressure gauge must be sized so the test pressure is at mid-scale.

Pipe support and protection: piping must be supported at intervals per code (typically every 6 ft/1.8 m for small sizes), protected from physical damage, and not run through ducts, chimneys, or elevator shafts.

Drip legs (sediment traps) are required at the inlet of appliances; the leg must be at least 3 in (75 mm) deep and installed downstream of the shutoff valve.

Every appliance must be installed per its certified listing and manufacturer's instructions; the data plate gives input rating, manifold pressure, orifice size, and clearances.

Manifold pressure: natural gas appliances typically 3.5 in w.c. (some 3.5–4.0 in w.c.); propane appliances typically 10–11 in w.c. Supply pressure at the appliance inlet must be within the manufacturer's specified range.

A manual shutoff valve must be installed in the supply line within 6 ft (1.8 m) of the appliance and be readily accessible and clearly identified.

A union or flanged connection is required between the shutoff valve and the appliance to allow removal; appliance connectors must be listed and protected from damage.

Clearances to combustibles: maintain the listed clearances on all sides and above; a clearance reduction requires a listed shield or approved non-combustible protection installed per code.

Appliance flue and draft hood must be properly connected and sized to the appliance; a draft hood must not be modified, and the relief opening must remain unobstructed.

For appliances installed in garages, ignition sources must be at least 18 in (450 mm) above the floor for propane (heavier than air) and the appliance protected from vehicle impact.

Combustion air and ventilation openings must not be obstructed; after installation, verify gas supply pressure, manifold pressure, draft, and complete combustion before leaving the site.

Thermocouples generate millivolts (typically 250–750 mV open circuit) from a pilot flame; the voltage holds the gas valve open via the safety magnet.

A thermopile generates higher voltage (typically 500–750 mV under load) and can power a millivolt gas valve and thermostat circuit without external power.

Flame rectification (flame sensing) uses the flame to conduct current between the sensor and burner; the control detects microamps (typically 1–10 µA) to prove flame.

Hot surface ignition (HSI) uses a silicon carbide or nitride igniter; test resistance with power off (typically 40–100 Ω, varies by manufacturer) and check for cracks.

Spark ignition (direct spark or intermittent pilot) requires a proper spark gap (typically 1/8 in/3 mm) and a good ground; a weak spark indicates a bad igniter, wire, or control.

Safety devices include: high-limit switch, rollout switch, blocked-vent pressure switch, flame rollout, and gas pressure switches; never bypass or jumper a safety device.

A rollout switch trips on flame rollout from a blocked flue or dirty burner; it is manual-reset and must be investigated before resetting.

Pressure switches prove draft or airflow; a stuck-open switch or blocked sensing tube causes ignition lockout or short cycling.

Diagnostic sequence: verify gas supply and pressure, then electrical supply and control voltage, then ignition sequence, then flame proving, then combustion and venting.

Pilot outage causes: dirty pilot orifice, misaligned pilot, weak thermocouple, draft/spillage, or gas supply interruption; clean or replace components rather than increasing pilot flame.

Short cycling often indicates a high-limit trip (restricted airflow, dirty filter, blocked flue) or a faulty thermostat/control; find the root cause, not just reset.

Burner maintenance: clean burner ports, check for rust, debris, or misalignment; a yellow lazy flame on natural gas indicates incomplete combustion and requires adjustment or cleaning.

Gas valve testing: check inlet and outlet pressures, verify the valve opens on call for heat, and confirm the operator coil or diaphragm operates; never disassemble a gas valve.

Manifold pressure must be set with a manometer with the appliance operating; adjust the regulator per the data plate and recheck after adjustment.

Soot deposits indicate incomplete combustion (rich mixture or blocked flue); soot is a fire and CO hazard and must be corrected, not just cleaned.

After service, perform a combustion test, leak test, and verify draft; document readings and leave the appliance operating safely.

CO is colourless, odourless, and slightly lighter than air; it binds haemoglobin about 200–250 times more readily than oxygen, causing tissue hypoxia.

Combustion analysis measures O2, CO2, CO, stack temperature, and ambient CO; calculate excess air and steady-state efficiency from these readings.

Target flue CO for natural gas appliances is typically under 100 ppm (air-free) for clean combustion; elevated CO indicates incomplete combustion.

CO2 max for natural gas ≈ 11.7–12% and for propane ≈ 13.8%; measured CO2 divided by CO2 max gives the percent of theoretical air used (or excess air = (CO2max/CO2measured − 1) × 100).

Dilution air lowers measured CO2 and raises measured O2; always convert CO readings to 'air-free' values for comparison.

Stack temperature rise plus O2/CO2 readings give steady-state efficiency; high stack temperature with low CO2 indicates excess air or heat exchanger fouling.

Indoor air quality hazards: spillage from natural draft appliances, backdrafting from exhaust fans, blocked vents, and unvented appliances; test for CO in the breathing zone.

CO alarm placement: outside sleeping areas and on each level; do not install within 5 ft of a fuel-burning appliance or in dead air spaces.

Personal protective equipment: safety glasses, gloves, and flame-resistant clothing when working on gas appliances; use a respirator when cutting or grinding.

Before working on gas piping, isolate and lock out/tag out the gas supply, and purge lines safely to a well-ventilated area.

Use a calibrated combustible gas detector (LEL meter) to check for leaks; soap bubbles confirm small leaks; never use a flame.

Tools: manometer for pressure testing, U-tube or digital; combustion analyzer for O2/CO/CO2/stack temperature; multimeter for electrical checks; thermocouple tester.

Confined space entry requires atmospheric testing for O2, combustible gas, and CO before entry, plus a standby attendant and permit.

Ladder safety: 4:1 rule (base 1 ft out for every 4 ft of height), three-point contact, and secure the ladder before climbing.

Electrical safety: lock out and tag out before servicing controls; verify with a meter that power is off; capacitor discharge before handling.

Jobsite housekeeping: keep combustibles away from appliances, protect openings, and secure cylinders upright with valves closed when not in use.

Document all work: date, appliance model and serial, readings (pressures, CO, draft), parts replaced, and tests performed; leave a copy with the customer.

Explain findings in plain language, present options and costs, and obtain approval before performing additional work.

A gasfitter must not perform work outside their licence class; refer to a qualified colleague or the authority when in doubt.

Confidentiality: customer information and property details must not be shared; obtain permission before taking photos.

Safety reporting: if a hazard is found (CO, gas leak, blocked vent), inform the occupant immediately, shut off the appliance if unsafe, and document the action taken.

Professional conduct includes punctuality, clean work area, respect for the customer's property, and honest communication about what was and was not done.

Invoices and work orders should reference the applicable code or manufacturer instruction when a repair or upgrade is required.

Follow-up: schedule a return visit for combustion analysis or leak recheck when a repair is made, and record the appointment.