Exam Cheat Sheet · Quick Reference
ICC G29 Master Mechanical Exam (2018 IMC/IFGC)
National · Pearson Vue
National State Portion 100 questions
Key Distinctions
Where a general requirement conflicts with a requirement written specifically for the appliance/installation, the specific requirement governs; the 'most restrictive governs' rule applies only where different sections specify different materials, methods or other requirements.
IMC 2018 Section 102.1In a high-probability system the design or location of components is such that leaked refrigerant will enter an occupancy-classified area other than the machinery room, while in a low-probability system such leakage will not enter the occupied area.
IMC 2018 Section 202 — High-Probability Systems'Labeled' means a label, seal, symbol or mark of a nationally recognized testing laboratory or approved agency that maintains periodic inspection of production has been affixed, while 'listed' means inclusion in a published list of an organization acceptable to the code official (and 'approved' means acceptable to the code official).
IMC 2018 Section 202 — Labeled/ListedAn eyebrow hood is mounted directly to the appliance face above the opening(s) from which effluent is emitted, extending past the sides and overhanging the front, whereas a backshelf hood is set back from the front of the appliance and closed to the rear, and a pass-over hood is a free-standing backshelf hood low enough to pass food over.
IMC 2018 Section 202 — Commercial Kitchen HoodsThe longest length method sizes every section using the longest length of piping from the point of delivery to the most remote outlet with the load of that section, while the branch length method sizes each branch using that branch's own length measured from the meter.
IFGC 2018 Section 402.4.1Type II uses Class II combustible liquid solvents with a flash point at or above 100°F and below 140°F, while Type III uses Class III combustible liquid solvents with a flash point at or above 140°F (Type I uses Class I solvents below 100°F; Types IV and V use Class IV nonflammable solvents).
IMC 2018 Section 202 — Dry Cleaning Systems / Combustible Liquid, and 12Welding on (repair of) pressure vessels must be performed by an R-Stamp holder per the National Board Inspection Code Part 3 or an approved standard, whereas the S-Stamp applies to new power boiler construction.
IMC 2018 Section 1003.3Per the IFGC 404.7 exception, black steel and galvanized steel piping are not required to be protected, while other piping concealed in light-frame assemblies and located less than 1-1/2 inches from the framing member face to which the wall, ceiling or floor membrane will be attached must be protected by steel shield plates not less than 0.0575 inch (No. 16 gage).
IFGC 2018 Section 404.7CSST without an arc-resistant jacket requires a bonding jumper not smaller than 6 AWG copper (or equivalent), while arc-resistant-jacketed CSST is considered bonded where it connects to an appliance that is connected to the appliance grounding conductor of the circuit supplying that appliance.
IFGC 2018 Section 310.2.2Where single-wall metal pipe passes through a combustible exterior wall, a listed draft-hood appliance needs a ventilated thimble not less than 4 inches larger in diameter (reduced to not less than 2 inches larger where there is a run of not less than 6 feet of pipe in the open between the draft hood outlet and the thimble), while an unlisted draft-hood appliance needs one not less than 6 inches larger (12 inches applies to residential and low-heat appliances).
IFGC 2018 Section 503.7.7Ammonia systems require a minimum emergency ventilation rate of 30 air changes per hour in accordance with IIAR 2, while non-ammonia systems use the formula Q = 100 × √G.
IMC 2018 Section 1105.6.3Piping systems with a design operating gas pressure greater than 2 psig must be purged outdoors; indoor purging (such as through an appliance burner) is allowed only for systems at 2 psig or less that also do not meet the size and length criteria of Table 406.7.1.1.
IFGC 2018 Section 406.7.1A single unvented room heater shall not have an input rating in excess of 40,000 Btu/h (IFGC 621.3), while the aggregate input of all unvented appliances is limited to 20 Btu/h per cubic foot of room volume (IFGC 621.5), which may include an adjacent space connected by an opening that cannot be closed.
IFGC 2018 Section 621.3Abrasive materials are moderately abrasive particulate in high concentrations and highly abrasive particulate in moderate and high concentrations (alumina, bauxite, iron silicate, sand, slag), while nonabrasive/abrasive materials cover nonabrasive particulate in high concentrations, moderately abrasive in low and moderate concentrations, and highly abrasive in low concentrations (alfalfa, asphalt, plaster, gypsum, salt).
IMC 2018 Section 202 — Abrasive Materials / Nonabrasive-Abrasive Materials, and 16Key Terms
Formulas to Know
Larger of 0.5 cfm per sq ft of machinery room area or 20 cfm per person; alternative criterion is the volume needed to limit room temperature rise to 18°F. Example: 1,000 sq ft, 2 occupants → 0.5 × 1,000 = 500 cfm vs 20 × 2 = 40 cfm, so 500 cfm governs.Q = 100 × √G, where G = design mass of refrigerant (lb) in the largest system with any part in the machinery room. Example: G = 900 lb → 100 × 30 = 3,000 cfm. (Ammonia instead uses 30 air changes per hour per IIAR 2.)Test at 1.5 × maximum system design pressure, but not less than 100 psi, for not less than 15 minutes. Example: 1.5 × 80 psi = 120 psi, which exceeds the 100 psi floor → 120 psi for 15 minutes.Test pressure = not less than 1½ times the proposed maximum working pressure, but not less than 3 psig, irrespective of design pressure; duration not less than 10 minutes for a system under 10 cubic feet volume or a system in a single-family dwelling. Mechanical gauge scale high end not greater than five times the test pressure (IFGC 406.4).cfh = Btu/h ÷ 1,000 (natural gas); a section carries the sum of the loads it serves. Examples: 40,000 + 100,000 = 140,000 Btuh = 140 cfh; meter demand = (80,000 + 40,000 + 30,000) ÷ 1,000 = 150 cfh.1 horsepower = 1 ton = 12,000 Btu/h. Example: 5 hp × 12,000 = 60,000 Btu/h.Not less than 4 cfm of outside ventilation air per 1,000 Btu/h of rated input. Example: 800,000 ÷ 1,000 × 4 = 3,200 cfm.Not more than 20 Btu/h per cubic foot of room volume; volume of an adjacent space connected by an opening that cannot be closed may be included. Example: (900 + 600) × 20 = 30,000 Btu/h aggregate.Minimum volume of 50 cubic feet per 1,000 Btu/h of appliance input rating.Not less than 1 cfm per 12 cubic feet of room volume. Example: 60 × 30 × 10 = 18,000 ft³ ÷ 12 = 1,500 cfm.