TSSA Gas Technician 2 (G2) cheat sheet

Natural gas is primarily methane (typically 90-95% by volume) with small amounts of ethane, propane, butane, and nitrogen; its relative density is about 0.60 (air = 1.0), so it is lighter than air and accumulates at high points.

Propane (C3H8) has a relative density of about 1.52 (air = 1.0), so leaks pool in low areas such as basements, pits, and crawl spaces.

Ideal gas law: P × V = n × R × T, where P is absolute pressure, V is volume, n is moles, R is the universal gas constant, and T is absolute temperature; use it to correct volume measurements to standard conditions.

Charles's law (V1/T1 = V2/T2 at constant pressure) and Boyle's law (P1 × V1 = P2 × V2 at constant temperature) explain why gas volume changes with temperature and pressure.

Heating value: natural gas is approximately 1,000 BTU per cubic foot (37.3 MJ/m³) at standard conditions; propane vapor is approximately 2,500 BTU per cubic foot (93 MJ/m³).

Complete combustion of methane: CH4 + 2 O2 → CO2 + 2 H2O; each volume of methane requires two volumes of oxygen, which is about 10 volumes of air (air is ~21% O2).

Incomplete combustion produces carbon monoxide (CO), a colorless, odorless, toxic gas; CO is produced when oxygen is insufficient, flame impingement occurs, or burners are misadjusted.

Flammable limits in air: methane approximately 5% to 15% by volume; propane approximately 2.1% to 9.5% by volume; concentrations between these limits can ignite if a source of ignition is present.

Liquefied petroleum gas (LPG) expands about 270 times in volume when vaporized from liquid to vapor at atmospheric pressure; a small liquid leak can produce a large flammable vapor cloud.

In Ontario, the Gas Utilization Code (GUC) is adopted under the Technical Standards and Safety Act, 2000 (TSSA Act); the GUC regulates gas utilization equipment and is enforced by TSSA.

CSA B149.1 (Natural Gas and Propane Installation Code) governs the installation of gas-burning appliances, piping, venting, and combustion air; CSA B149.2 covers propane storage and handling.

The TSSA Gas Technician 2 (G2) certificate permits work on gas appliances and systems up to and including 400,000 BTU/h input, under the supervision of a G1 holder where required by regulation.

A TSSA Gas Technician 3 (G3) may work only on appliances up to 120,000 BTU/h input and must be supervised by a G2 or G1 holder; a G1 may work on any size appliance.

The Ontario Electrical Safety Code (OESC) and CSA C22.1 apply to electrical connections to gas appliances; gas technicians must not perform electrical work beyond the scope permitted by their certificate.

Manufacturer's certified installation instructions must be followed and take precedence where they are more restrictive than the code; the appliance certification mark (e.g., CSA, ULC, cETL) confirms the appliance is approved for use in Canada.

A permit from TSSA (or the local authority having jurisdiction) is required before installing, altering, or replacing gas piping or appliances in most jurisdictions; the permit number must be posted on site.

The Gas Code requires that every gas appliance be connected to a venting system approved for the appliance category (Category I, II, III, or IV) and that the venting system be installed per the manufacturer's instructions and B149.1.

Clearances to combustible material are specified in the appliance's certified listing and in B149.1; reducing required clearances without an approved method (e.g., a listed clearance-reduction shield) is a code violation.

Schedule 40 black steel pipe is the standard material for natural gas piping; it must be joined with malleable iron fittings and pipe dope approved for gas service, applied to male threads only.

Copper tubing (Type L or K) may be used for natural gas in some jurisdictions but is prohibited for propane in many codes because propane can react with copper; always verify local code and appliance approval.

Corrugated stainless steel tubing (CSST) must be installed per the manufacturer's instructions and bonded to the electrical grounding system per the manufacturer's requirements and the electrical code.

Pipe sizing for natural gas is based on the total connected load, the allowable pressure drop, and the equivalent length of the longest run; use the pipe sizing tables in B149.1 or the manufacturer's sizing tables.

A manual shutoff valve must be installed upstream of and within sight of each appliance, and a union or flanged connection must be provided for appliance removal.

A drip leg (sediment trap) must be installed at the lowest point of the piping near the appliance to collect moisture and debris; it must be accessible for cleaning.

Gas piping must be supported at intervals not exceeding those specified in the code (typically every 3 m / 10 ft for horizontal runs) and must not be concealed in a way that prevents inspection.

Pressure testing of new or altered gas piping is performed with air or inert gas at a pressure specified by the code (often 1.5 times the working pressure, but not less than 3 psi for low-pressure systems) and must hold for the required duration without leakage.

Piping must not be installed in elevator shafts, stairwells, or concealed spaces that are not ventilated, and must be protected from physical damage where it passes through walls or floors.

Category I appliances are non-condensing, operate with a negative vent pressure, and require a vertical vent; Category II are condensing and negative pressure; Category III are condensing and positive pressure; Category IV are non-condensing and positive pressure.

Combustion air requirements: for conventional appliances, provide 50 cubic feet (1.42 m³) of free air per 1,000 BTU/h input; for tight construction, use the indoor air method or direct-vent method per B149.1.

When using the indoor air method, the total input of all appliances in the space must not exceed the allowable input based on the volume of the space and the air infiltration rate.

A vent connector must slope upward toward the chimney or vent at not less than 1/4 inch per foot (20 mm/m) for natural gas and propane appliances, and must be as short and straight as possible.

The vent termination must be located at least 1 m (3 ft) above any forced-air inlet located within 3 m (10 ft), and at least 1 m (3 ft) from any window, door, or gravity air inlet, unless otherwise permitted by the manufacturer.

A draft hood or draft diverter must be installed on Category I appliances as specified by the manufacturer; it is not permitted on direct-vent or positive-pressure appliances.

Direct-vent appliances must be installed with the manufacturer's certified venting system; the vent termination must maintain clearances to combustibles and to other building openings as specified in the installation instructions.

Appliances installed in confined spaces must have two permanent openings (one near the top, one near the bottom) sized per B149.1, or be provided with a ducted combustion air supply.

Clearances to combustible material around appliance and vent must be maintained as certified; use listed thimbles, shields, or double-wall vent where required to reduce clearance.

A combustion analyzer measures oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO), and flue gas temperature; use these readings to calculate excess air, efficiency, and CO air-free.

CO air-free (COAF) is calculated as CO measured × (20.9 / (20.9 - O2 measured)); a COAF above 100 ppm (or the manufacturer's limit) indicates incomplete combustion and requires correction.

Steady-state efficiency can be estimated from flue gas temperature and CO2; a typical natural gas appliance with 6% CO2 and 200°F flue temperature has an efficiency of approximately 80%.

Gas pressure testing: use a manometer or calibrated gauge; check supply pressure with the appliance operating and all other appliances on the same meter operating, to confirm minimum and maximum pressures are within the appliance's rating plate.

Clock the gas meter to verify input rate: time one revolution of the meter dial (or a measured volume) and calculate BTU/h = (volume in ft³ × heating value in BTU/ft³) / time in minutes × 60.

Troubleshooting flame problems: a lazy yellow flame indicates insufficient primary air, a blocked burner orifice, or high gas pressure; a lifting flame indicates excessive primary air or high pressure; a roaring flame indicates overfiring.

Check the thermocouple or flame sensor: a thermocouple should generate approximately 25-30 mV open circuit and 10-15 mV under load; a flame sensor should read a minimum of 1-2 microamps (varies by control).

When servicing, always shut off the gas supply, lock out/tag out, and verify no gas leakage with a combustible gas detector or soap solution before returning the appliance to service.

Commissioning includes verifying venting, combustion air, gas pressure, manifold pressure, temperature rise (for furnaces), and completing a combustion analysis; record all readings on the commissioning report.