Virginia Residential HVAC
Practice at the real exam's pace
Every practice exam shows your time per question against the real exam's clock (2:10 here), and each topic lands in one of these:
What's on the exam
Questions per topic, out of 55Topics
Standards of Practice
All material comes from the Virginia Board for Contractors Individual License and Certification Regulations, 18 VAC 50-30.
Key Concepts
Working on an expired license (18 VAC 50-30-130 E, Page 24). Any regulated activity conducted subsequent to the expiration of the license may constitute unlicensed activity and may be subject to prosecution under Chapter 1 (§ 54.1-100 et seq.) or Chapter 11 (§ 54.1-1100 et seq.) of Title 54.1 of the Code of Virginia. The SOURCE states no grace period.
Denial of reinstatement and review rights (18 VAC 50-30-130 F, Page 24). The board may deny reinstatement of a license or certification for the same reasons it may refuse initial licensure or certification or discipline a regulant. The regulant has…
Standards of Conduct
Key Concepts
Grounds for disciplinary action — 18 VAC 50-30-185 (Page 26). The board may impose remedial education, a monetary penalty in accordance with § 54.1-202 A of the Code of Virginia, or revoke, suspend, or refuse to renew any license or certification when the licensee or certificate holder has been found to have violated or cooperated with others in violating any provision of Chapter 1 (§ 54.1-100 et seq.) or Chapter 11 (§ 54.1-1100 et seq.) of Title 54.1 of the Code of Virginia or the regulations of the board.
Prohibited acts — 18 VAC 50-30-190 (Pages 26–27). Any violation may result in disciplinary action. Key items for this exam:
Renewal and Reinstatement
Key Concepts
License expiration — three years (18 VAC 50-30-120 A, Part III, Book Page 21) Licenses issued under this chapter to electricians, gas fitters, liquefied petroleum gas fitters, natural gas fitter providers, HVAC tradesmen, or plumbers expire three years from the last day of the month in which they were issued, as indicated on the license.
Two-year expiration applies to everything else (18 VAC 50-30-120 B) Except as otherwise provided in the chapter, all other licenses and certifications issued under the chapter expire two years from the last day of the month in which they were issued. This does not apply to tradesman licenses.
Definitions
Key Concepts
Appliance type — temperature at point of entrance to the flue (normal operating conditions) — IMC 2021, Chapter 2 Definitions, "Appliance Type," Page 2-2: - Low-heat appliance (residential appliance): temperature of 1,000ºF (538ºC) or less. - Medium-heat appliance: more than 1,000ºF (538ºC), but not greater than 2,000ºF (1093ºC). - High-heat appliance: greater than 2,000ºF (1093ºC).
Joints — IMC 2021 Section 202: - Joint, soldered: a gas-tight joint joining metal parts with metallic mixtures of alloys that melt between 400ºF (204ºC) and 1,000ºF (538ºC) (Page 2-7). - Brazed joint: gas-tight joint with alloys melting above 1,000ºF (538ºC) but lower than the melting temperature of the parts to be joined (Page 2-2). Brazing uses a nonferrous filler metal melting…
Qualification for Licensure
Virginia – Residential HVAC · 1 question (2% of the exam)
Key Concepts
- Residential HVAC tradesman experience/education schedule. An applicant for examination as a residential HVAC tradesman (or residential plumber tradesman) must meet one of five education/experience combinations — e.g., 80 hours of formal vocational training + four years of practical experience (18 VAC 50-30-39 A, Pages 10–11).
- Journeyman schedule is separate and longer. An applicant for examination as a journeyman electrician, plumber, or HVAC tradesman with 240 hours of formal vocational training must have four years of practical experience (18 VAC 50-30-39 B, Page 11).
- Master trade license. Qualify by (1) holding a valid residential HVAC tradesman or residential plumber tradesman license in the trade…
Warm Air Heating
Key Concepts
Gas furnace combustion checks (Section 33.2.4) - Natural gas manifold pressure: 3.5 in. WC; LP gas: 10.5 in. WC (Page 760). Gas pressure is measured in inches of water column. - ANSI permits a maximum of 400 ppm carbon monoxide in furnace flue gas; many manufacturers treat anything above 50 ppm as indicating a problem (Page 759). - Net stack temperature for noncondensing furnaces: 325°F to 500°F (163°C–260°C). Condensing furnaces: less than 140°F (60°C) (Page 760). - LP gas ignition temperature: 920°F to 1020°F (493°C–549°C); natural gas: 1100°F to 1200°F (Section 33.2.1, Page 757). - Combustion air: 10 ft³ of air burns 1 ft³ of natural gas (about 15 ft³ used to give 50% excess air); **24…
Ventilation Systems
Key Concepts
Dryer exhaust (IMC 2021, Section 504) — the most heavily tested cluster in the verified questions:
- Maximum exhaust duct length is 35 feet from the connection to the transition duct to the outlet terminal, with reductions for fittings from Table 504.9.4.1 (Section 504.9.4.1).
- Where equivalent length exceeds 35 feet, a permanent label or tag identifying the equivalent length must be located within 6 feet of the exhaust duct connection (Section 504.9.5).
- Transition duct: a single length listed and labeled to UL 2158A, not greater than 8 feet, and not concealed within construction (Section 504.9.3).
- Duct material: metal not less than 0.016 inch (0.4 mm) thick, smooth interior finish, 4-inch nominal diameter (Section 504.9.1).…
Air Conditioning Systems
Key Concepts
High side / low side. The high side starts at the compressor's discharge valve and extends through the condenser and liquid line to the metering device; the metering device is the divider between high and low sides, and the filter-drier sits within the liquid line (still on the high side). (Modern Refrigeration and Air Conditioning, 22nd ed., Section 8.1.1 and Figure 8-2, Pages 126–127)
Line identification. In a split air-conditioning system the two lines are the liquid line and the suction line; the larger line is the suction line, the smaller is the liquid line. The term "gas line" is reserved for the larger line in a heat pump, because it always carries gas. *(22nd ed., Chapter…
Duct Systems
Key Concepts
Duct sizing procedure (Manual D–based). Modern Refrigeration and Air Conditioning, Section 30.5, gives the sequence: obtain room-by-room loads, obtain blower data, determine external static pressure (ESP), calculate device pressure losses (DPL), calculate available static pressure (ASP), sketch the system, calculate total effective length (TEL), calculate design friction rate, calculate design air quantity, then use a friction chart or duct calculator (p. 684; blower/ASP discussion p. 685).
Available static pressure. ASP = ESP − DPL. ASP measures the resistance the ductwork is designed to provide and is used to design the longest duct run (p. 685).
Chimneys, Flues, and Vents
Key Concepts
Code authority and scope (IMC 2021, Chapter 8) - Chapter 8 governs factory-built chimneys, chimney liners, vents and connectors, and the utilization of masonry chimneys. Gas-fired appliances shall be vented in accordance with the International Fuel Gas Code (IMC 801.1). - Oil-fired appliances shall be vented in accordance with this code and NFPA 31 (IMC 801.2.1). Modern Refrigeration and Air Conditioning (22nd ed.), Page 816, states the same: the IMC requires oil-fired appliances to be vented per NFPA 31, Standard for the Installation of Oil-Burning Equipment. - Every fuel-burning appliance shall discharge products of combustion to a vent, factory-built chimney or masonry chimney, except appliances vented per Section 804 (IMC 801.2).
Hot Water Heaters
3 questions, 5% of the exam
Key Concepts
Water heater standards (Section 1002.1). Potable water heaters and hot water storage tanks shall be listed and labeled and installed per the manufacturer's instructions, the International Plumbing Code and this code. Product standards: - Domestic electric — UL 174 or UL 1453 - Commercial electric — UL 1453 - Oil-fired — UL 732 - Solid-fuel-fired — UL 2523 - Solar thermal systems — Chapter 14 and ICC 900/SRCC 300
Water heaters shall be capable of being removed without first removing a permanent portion of the building structure.
Hot Water Piping
Key Concepts
Materials and ratings (IMC 2021 Ch. 12) - Hydronic pipe shall conform to the standards in Table 1202.4 (copper/copper-alloy tube Type K, L or M; PEX; PE-RT; CPVC; PVC; PP; steel pipe and tubing; ductile iron; etc.). The exterior of the pipe shall be protected from corrosion and degradation (1202.4). - Materials shall be rated for the operating temperature and pressure of the system and suitable for the fluid (1202.3). Reused pipe, fittings and valves must be clean, free from foreign materials and approved by the code official (1202.2) — but reused materials are not permitted in ground-source heat pump loop systems (1210.2).
Combustion Air
Virginia Residential HVAC
Key Concepts
Air required for combustion (Ch. 33, p. 758 / 20th ed. p. 1119) - To burn 1 ft³ of natural gas, 10 ft³ of air is required for complete combustion. About 15 ft³ of air is used per cubic foot of natural gas, which provides 50% excess air. - To burn 1 ft³ of LP gas, 24 ft³ of air is required. About 35 ft³ of air is needed to provide 50% excess air. - Burning 1 ft³ of natural gas with 15 ft³ of air yields about 1 ft³ of carbon dioxide, 2 ft³ of water vapor, 12 ft³ of nitrogen and 1 ft³ of oxygen.
Controls/Low Voltage
Key Concepts
Ladder diagrams. The two vertical lines (rails) represent the voltage supplied to the circuit; the horizontal lines (rungs) are individual circuits, each containing a load and the switches, relays or contacts that control it. Switching devices are generally on the left of a rung, and generally each rung has only one load, shown as the right-most symbol. Rail voltages are often 24 V for low-voltage control circuits, 120 V or 240 V single-phase, and 208 V, 277 V or 480 V three-phase. (22nd ed., Ch. 18, p. 368, Sec. 18.2.1)
Fuel Oil Piping and Storage
Key Concepts
Joints and connections (IMC 2021 §1303.1). Threaded joints must be made tight with suitable lubricant or pipe compound. Prohibited in oil lines: unions requiring gaskets or packings, right or left couplings, and sweat fittings employing solder having a melting point of less than 1,000°F (538°C). Cast-iron fittings shall not be used. Pipe ends must be cut square, reamed and chamfered, free of burrs, with full-bore openings and no undercutting (§1303.2).
System sizing (§1305.1). Minimum supply line: 3/8-inch (9.5 mm) inside diameter nominal pipe or 3/8-inch (9.5 mm) outside diameter tubing. Minimum return line: 1/4-inch (6.4 mm) inside diameter nominal pipe or 5/16-inch (7.9 mm) outside diameter tubing. Copper tubing shall have 0.035-inch (0.9 mm) nominal and 0.032-inch…
Insulation
Key Concepts
Thermal conductivity (K-value). A material's K-value measures the amount of heat that will pass through one square foot of the material one inch thick, in one hour, when there is a 1°F temperature difference between the two sides. Units are Btu·in/hr·ft²·°F. (Modern Refrigeration and Air Conditioning, 22nd ed., Ch. 32, p. 717)
Thermal conductance (C-value). The C-value measures the amount of heat passing through one square foot of the component in one hour at a 1°F temperature difference, but it is not based on a 1" thickness — it describes the material at its actual measured thickness. C-values are usually looked up on a chart but can be calculated from the K-value and the thickness. *(22nd ed.,…
Refrigerants
Key Concepts
Chemical classification (Modern Refrigeration and Air Conditioning, 22nd ed., Ch. 10, "Classifying Refrigerants," pp. 163–164): - CFCs — chlorine, fluorine, carbon; fully halogenated (all hydrogen replaced by halogens); high ODP. Examples R-11, R-12. Not manufactured in developed countries since the end of 1995, but may still be found in equipment produced before 1995. - HCFCs — hydrogen, chlorine, fluorine, carbon; partially halogenated, so less ozone depletion than CFCs. Examples R-22, R-123. - HFCs — hydrogen, fluorine, carbon, no chlorine atoms; considered to have zero ODP. Examples R-134a, R-32, R-152a, R-404A. Some HFCs still have high GWP. - HFOs — hydrogen, fluorine, carbon with at least one double carbon bond; zero ODP and very low GWP; mildly flammable,…
Refrigerant Piping
Key Concepts
Tubing preparation and bending - The minimum radius for a 90° bend in copper tubing is five times the diameter of the tubing (Modern Refrigeration and Air Conditioning, 22nd ed., Section 5.4 Bending Tubing, Page 76, Figure 5-13). Example from the text: 1/2" tubing requires a 2 1/2" minimum radius. Tighter radii risk kinking, flattening or buckling, which interferes with refrigerant flow and pressure. - Bend slowly and gradually; use as large a radius as possible, which reduces flattening. Bending springs may be used inside or outside the tubing; a lever-type bender shown in Section 5.4 handles 1/4", 5/16" and 3/8" tubing (Page 77). - Cutting leaves burrs that must be removed by reaming. File the end…
Chilled and Condenser Water Piping
Key Concepts
Scope of hydronic piping rules. IMC Section 1201.1 governs construction, installation, alteration and repair of hydronic piping that is part of HVAC systems, including steam, hot water, chilled water, steam condensate and ground-source heat pump loop systems. Potable cold and hot water distribution is covered by the International Plumbing Code. Piping and components are sized for the demand of the system (1201.2). As an alternative to Sections 1202 and 1203, piping may be designed, installed, inspected and tested per ASME B31.9 (1201.3).
Firestopping/Penetration Inspection
Virginia – Residential HVAC
Key Concepts
Duct penetrations through the dwelling/garage separation (IMC 603.7). Ducts in a private garage that penetrate a wall or ceiling separating a dwelling from a private garage shall be continuous, shall be constructed of sheet steel having a thickness of not less than 0.0187 inch (0.4712 mm) (No. 26 gage) and shall not have openings into the garage. Fire and smoke dampers are not required in such ducts passing through that wall or ceiling except where required by Chapter 7 of the International Building Code. Note also that duct system penetrations of walls, floors, ceilings and roofs, and air transfer openings in those components, shall be protected as required by Section 607.