Exam Cheat Sheet · Quick Reference
Kansas City, MO Master Mechanical Exam (ICC G29, 2018 IMC/IFGC)
Missouri · Pearson Vue
Missouri State Portion 100 questions
Key Distinctions
Where a general requirement conflicts with a requirement written specifically for the appliance or 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, whereas 'listed' means inclusion in a published list of an organization acceptable to the code official.
IMC 2018 Section 202 — Labeled/ListedThe longest length method sizes every section using the longest length of piping from the point of delivery to the most remote outlet plus that section's load, while the branch length method sizes each branch using that branch's own length measured from the meter and sizes mains by the length to the most remote outlet they serve.
IFGC 2018 Section 402.4.1Single-wall metal vent pipe through a combustible exterior wall needs a thimble not less than 4 inches larger in diameter for listed draft-hood appliances (reduced to not less than 2 inches larger where a run of not less than 6 feet of pipe is in the open between the draft hood outlet and the thimble), but not less than 6 inches larger for unlisted draft-hood appliances.
IFGC 2018 Section 503.7.7Ammonia machinery rooms require a minimum emergency ventilation rate of 30 air changes per hour in accordance with IIAR 2, while other refrigerants use the equation Q = 100 × √G.
IMC 2018 Section 1105.6.3A single unvented room heater shall not have an input rating in excess of 40,000 Btu/h, while the aggregate input of all unvented appliances in a room is limited to 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).
IFGC 2018 Section 621.3Black steel and galvanized steel piping are exempted by the Section 404.7 exception from the fastener-protection requirement, while other piping must be protected by steel shield plates not less than 0.0575 inch (No. 16 gage) thick.
IFGC 2018 Section 404.7CSST without an arc-resistant jacket requires a bonding jumper not smaller than 6 AWG copper wire 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 310.2.2Piping 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 406.7.1Detached one- and two-family dwellings and townhouses not more than three stories high with separate means of egress, and their accessory structures, follow the IRC, while apartment buildings and townhouses exceeding three stories remain under the IMC.
IMC 2018 Section 101.2Type II systems use Class II combustible liquid solvents with a flash point at or above 100°F and below 140°F, while Type III systems use Class III solvents with a flash point at or above 140°F (Type I uses Class I flammable solvents below 100°F).
IMC 2018 Section 202 — Dry Cleaning Systems / Combustible Liquid, and 12Key Terms
Formulas to Know
Larger of 0.5 cfm per square foot 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 is the design mass of refrigerant in pounds in the largest system having any part in the machinery room. Example: G = 900 lb → Q = 100 × 30 = 3,000 cfm. (Ammonia instead uses 30 air changes per hour.)Test at 1.5 × maximum system design pressure, but not less than 100 psi, for not less than 15 minutes. Example: 80 psi design → 1.5 × 80 = 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 of less than 10 cubic feet volume or in a single-family dwelling; test gauge scale maximum not greater than five times the test pressure.QOA = 0.01 × Afloor + 7.5 × (Nbr + 1). Example: 2,400 sq ft, 4 bedrooms → 0.01(2,400) + 7.5(5) = 24 + 37.5 = 61.5 cfm.Not less than 1 cfm per 12 cubic feet of room volume. Examples: 60 × 30 × 10 = 18,000 ft³ ÷ 12 = 1,500 cfm; 9,600 ft³ ÷ 12 = 800 cfm.Not less than 4 cfm per 1,000 Btu/h of rated input. Example: 800,000 Btu/h ÷ 1,000 × 4 = 3,200 cfm.Each of the two permanent openings: free area not less than 0.5 sq ft per 1,000 cubic feet of garage volume; where grille design/free area is unknown, metal louvers and grilles are assumed 75-percent free area (wood louvers 25 percent). Example: 18,000 ft³ → 18,000/1,000 × 0.5 = 9 sq ft net free area ÷ 0.75 = 12 sq ft gross each. Appliance output capacity limit: 4 scfm of hydrogen per 250 sq ft of floor area (500 sq ft → 8 scfm), with such naturally ventilated locations limited to 850 sq ft maximum floor area.cfh = total connected Btu/h of the section ÷ 1,000; size each section from the applicable table row (longest length row for the longest length method). Examples: 40,000 + 100,000 = 140,000 Btuh = 140 cfh (50-ft row: 3/4 in carries 151 cfh); 80,000 + 40,000 + 30,000 = 150 cfh total meter demand.Maximum straight duct = 35 ft maximum total equivalent length − sum of fitting equivalent lengths. Example: two 4-in radius mitered 90° elbows (5 ft each) + one 4-in radius mitered 45° elbow (2 ft 6 in) = 12 ft 6 in; 35 − 12.5 = 22 ft 6 in.