TSSA G2 Gas Technician Practice Test
Free · 148 Questions.

• Up to and including 400,000 BTU/h (120 kW) firing input capacity
• Up to and including 250,000 BTU/h (75 kW) maximum input capacity
• Up to and including 1,000,000 BTU/h (300 kW) total input capacity
• Unlimited firing capacity on heavy industrial burner systems

Why: Under O. Reg. 215/01, s. 21(1), the holder of a G.2 certificate may install, inspect, alter, purge, activate, repair, service or remove a natural gas or propane appliance with an input of 400,000 Btuh or less, together with the equipment and accessories essential to its operation. Appliances of any input fall under the G.1 certificate (s. 20(1)).

• The secondary supply air blower high-limit thermal safety switch
• The differential pressure switch proving adequate inducer draft
• The hydronic boiler low-water cut-off probe located on the header
• The ambient room humidistat contact switch mounted in the return

Why: The differential pressure switch senses the negative draft created by the induced draft blower wheel; it must close to prove adequate combustion venting before ignition can proceed.

• It is 0.10 in. w.c., which is well within the rating plate maximum
• It is 0.30 in. w.c., the average of the two readings, so within the maximum
• It is 0.60 in. w.c., which exceeds the rating plate maximum of 0.50 in. w.c.
• It is 0.60 in. w.c., which is acceptable because the maximum covers cooling mode

Why: Total external static pressure is the sum of the supply (positive) and return (negative) readings ignoring the sign: 0.35 + 0.25 = 0.60 in. w.c. (the manufacturer's example: -0.1 and +0.3 gives 0.4 in. w.c.). That is above the 0.50 in. w.c. rating plate maximum. Too much external static reduces airflow, which causes excessive temperature rise, limit switch tripping and heat exchanger failure, so check closed dampers or registers, filters and undersized or poorly laid out ductwork. Subtracting the readings or averaging them is wrong, and the maximum applies in heating as well.

• The test counts for the October 15 to April 30 heating season, and the tag expires May 1
• The test is invalid because it was done outside October 15 to April 30 and must be repeated
• The tag expires September 30 of the same year, before the heating season starts
• The tag is valid for a full 12 months, running from the date of the July test

Why: Clause 7.1.12.1(g) says a boiler tested between May 1 and October 14 (the off-season) is considered a valid test for the following October 15 to April 30 period. Clause (f) says the tag expires May 1 following completion of the requirement.

• When the boiler is fuelled with commercial propane rather than natural gas
• On residential domestic potable water storage tanks in single-family homes
• When input exceeds 400,000 BTU/h or radiation sits below boiler level
• LWCO devices are optional recommendations, not mandated by the Code

Why: In Ontario an automatically fired hot-water heating boiler must have a low-water cut-off when its input exceeds 120 kW (400,000 Btu/h) or when portions of the circulating system are located below the boiler's lowest safe permissible water level, regardless of input (with exemptions for bottom connections and piping within 2 m of the boiler, and for residential combo fan coil or in-floor heating, which instead need a flow-sensing device).