State HVAC License Prep

Exam blueprint

Sourced from IMC + IFGC (current state-adopted edition) + ACCA Manuals J/D/S + state HVAC license law (varies)

• Refrigeration cycle + system components20%
• Manual J load calculation fundamentals10%
• Manual D duct design fundamentals15%
• IFGC fuel-gas piping (sizing, support, pressure test)15%
• IMC mechanical (combustion air, venting, code chapters)15%
• Electrical for HVAC (motor circuits, low-voltage controls)10%
• Business + jurisdiction-specific law10%
• EPA 608 cross-reference (see sister credential)5%

1. 01The refrigeration cycle — core system theory

   ~90min

   Every state HVAC exam tests refrigeration-cycle fundamentals. Compressor → condenser → metering device → evaporator → back to compressor. Master the pressure-temperature relationship, superheat, subcooling, and the role of each component.

   • The four stages of the vapor-compression cycle

     (1) COMPRESSION: low-pressure low-temperature vapor enters the COMPRESSOR; leaves as high-pressure HIGH-TEMPERATURE vapor. (2) CONDENSATION: hot vapor enters the CONDENSER (outdoor coil in a typical AC); rejects heat to outdoor air; condenses into high-pressure liquid. (3) EXPANSION: liquid passes through the METERING DEVICE (TXV, fixed orifice, or EEV); pressure drops sharply, causing some liquid to flash to vapor and the temperature to plummet. (4) EVAPORATION: low-pressure cold mixture enters the EVAPORATOR (indoor coil); absorbs heat from indoor air; vaporizes completely back to vapor. Returns to compressor. The PRESSURE-TEMPERATURE RELATIONSHIP for a saturated refrigerant is fixed by the refrigerant's properties — that is why pressure gauges with refrigerant-specific scales also act as thermometers (saturation temperature at the gauged pressure).

   • Superheat and subcooling — the two health checks

     SUPERHEAT = how many degrees ABOVE saturation temperature the vapor leaves the evaporator. Measured at the suction line, near the evaporator outlet. Target on a fixed-orifice system: 8-15°F. Too LOW = liquid floodback (compressor damage); too HIGH = undercharge or restriction. SUBCOOLING = how many degrees BELOW saturation temperature the liquid leaves the condenser. Measured at the liquid line, near the condenser outlet. Target on a TXV system: 8-12°F. Too LOW = undercharge; too HIGH = overcharge. The technician's rule: TXV systems are charged BY SUBCOOLING; fixed-orifice systems are charged BY SUPERHEAT. Memorize both targets and which one to use — the exam tests which method goes with which metering device.

   • Component identification and failure modes

     COMPRESSOR types: scroll (most common in residential, ~95% efficient at design), reciprocating (older), rotary (small systems and heat pumps). RECIPROCATING failure modes: valve failure (low capacity), bearing wear (noisy, slows down). SCROLL failure: shorted windings (electrical), failed bearings (rare, usually fatal). METERING DEVICES: TXV (sensing bulb on suction line, modulates with load), fixed orifice / piston (cheap, limited operating range), EEV (electronic — replaces TXV in modern equipment, most precise). Failed TXV bulb = no superheat control = liquid floodback or starvation. CONDENSER types: tube-and-fin (residential), microchannel (modern, more efficient, harder to repair). EVAPORATOR types: A-coil, slab, N-coil. Recognize them in pictures — exam loves "identify this component in this photo" questions.

   Practice questions (2)

   1. 1. A residential AC system uses a thermostatic expansion valve (TXV). Which measurement is used to confirm the system is properly charged?

      • A.Superheat
      • B.Subcooling✓ correct
      • C.Discharge pressure alone
      • D.Suction line temperature alone

      TXV systems modulate the metering device to MAINTAIN a target superheat — so superheat is held constant by the valve and is NOT a useful charge indicator. Instead, charge is verified by SUBCOOLING measured at the liquid line (typical target 8-12°F). Fixed-orifice systems work the opposite way: they have a constant flow restriction, so superheat varies with charge and IS the charging metric. Discharge pressure or suction temperature alone are insufficient because both vary with outdoor temp.

   2. 2. A technician measures 4°F of superheat on a fixed-orifice system. Most likely cause?

      • A.System is properly charged
      • B.Overcharged refrigerant — liquid floodback risk✓ correct
      • C.Undercharged refrigerant
      • D.Indoor coil is too clean

      Target superheat for fixed-orifice in cooling at design conditions is typically 8-15°F. 4°F is well BELOW target, indicating refrigerant flooding into the suction line — classic overcharge. Liquid floodback can damage the compressor by hydraulic shock. Undercharge would produce HIGH superheat (vapor leaves the coil before fully heated by full coil contact). A clean indoor coil increases superheat slightly, not decreases.

2. 02Manual J + Manual D — sizing the system and the ducts

   ~105min

   ACCA's Manual J (load calc) and Manual D (duct design) are referenced by IECC + IRC and are testable on most state HVAC exams. You don't do a full Manual J calculation under exam time pressure — but you do answer the principles.

   • Manual J — heat loss + heat gain calculation

     Manual J (Residential Load Calculation) sums heat transfer from each building component to produce a HEAT LOSS (winter design day) and HEAT GAIN (summer design day) for each room and the whole building. Components: walls (U-value × area × ΔT), windows (U-value × area × ΔT, plus solar gain in summer), ceilings, floors, infiltration (air changes per hour × volume × ΔT). Internal gains in summer: people (~230 BTU/hr sensible per occupant), appliances, lighting. Result: design block load in BTU/hr that drives equipment sizing per Manual S. Common rule of thumb (NOT a substitute for Manual J): tight modern home ~20-25 BTU/hr per sq ft cooling; older/leakier ~30-40 BTU/hr/sq ft. Always: SIZE BY MANUAL J, never by sq ft alone — oversized AC short-cycles, runs sticky, fails to dehumidify.

     Reference: ACCA Manual J 8th Edition (current)

   • Manual D — duct sizing fundamentals

     Manual D (Residential Duct Systems) sizes ductwork given the equipment's rated CFM and external static pressure budget. Three-step process: (1) calculate total external static pressure (ESP) the equipment can deliver at design CFM (typically 0.5 in. WC for residential furnaces); (2) subtract pressure drops for accessories (filter ~0.10, coil ~0.15, registers ~0.05) to get the AVAILABLE static pressure for the supply + return ductwork; (3) use friction-rate tables (Manual D Appendix) or a duct calculator to size each duct run for the design CFM at the available friction rate (typically 0.06-0.10 in. WC per 100 ft). Rectangular vs round equivalency is often tested: a 12×6 rectangular duct ≈ 8.4-inch round equivalent for similar friction. Round is more efficient (less surface area per CFM, less friction).

     Reference: ACCA Manual D 3rd Edition (current)

   • Duct air velocity and noise

     Air velocity in residential ducts: SUPPLY MAINS 700-900 fpm (feet per minute); SUPPLY BRANCHES 600-700 fpm; RETURN MAINS 500-700 fpm; SUPPLY GRILLES 500-700 fpm at the face. Higher velocities = more friction loss + more noise. The "whoosh" complaint at supply registers is almost always over-velocity (oversized blower / undersized duct). Stripped-out velocities also matter on the equipment side: condensate-drain trap geometry, return-air filter sizing (typically 250 fpm face velocity at filter to avoid pulling drywall paper through into the coil). The exam loves "given equipment X CFM and duct Y inches, calculate velocity" — formula: V = CFM / (Area in sq ft). Convert duct area carefully: a 12×6 rectangular duct = 0.5 sq ft.

   Practice questions (2)

   1. 1. A residential air handler is rated at 1,200 CFM. The supply main is a 14×8 rectangular duct. Approximate air velocity in the supply main?

      • A.800 fpm
      • B.1,000 fpm
      • C.1,540 fpm✓ correct
      • D.12,000 fpm

      Duct area = 14 × 8 = 112 sq in. Convert to sq ft: 112 / 144 = 0.778 sq ft. Velocity = CFM / Area = 1,200 / 0.778 = ~1,540 fpm. That is above residential design recommendations (700-900 fpm for supply mains), suggesting either an oversized blower or undersized duct. 12,000 fpm forgets to convert sq in to sq ft (the most common error). 800 and 1,000 fpm assume a larger duct than what is given.

   2. 2. A 2,000-sq-ft modern, well-sealed home in a moderate climate is most likely to have a Manual J cooling design load close to:

      • A.10,000 BTU/hr (less than 1 ton)
      • B.40,000-50,000 BTU/hr (3-4 tons)✓ correct
      • C.60,000-80,000 BTU/hr (5-6 tons)
      • D.100,000 BTU/hr (8+ tons)

      Modern tight homes typically calculate at 20-25 BTU/hr per sq ft for cooling. 2,000 × 22 ≈ 44,000 BTU/hr ≈ 3.7 tons. Option B (40,000-50,000 BTU/hr) is the realistic Manual J ballpark. 10,000 BTU/hr is implausibly low (would not handle two rooms). Options C and D reflect common over-sizing-by-rule-of-thumb errors that lead to short-cycling and humidity problems — Manual J consistently produces SMALLER loads than installer-rule-of-thumb sizing.

3. 03IFGC fuel-gas piping — sizing, support, pressure test

   ~75min

   The International Fuel Gas Code governs natural-gas and propane piping for residential and commercial appliances. The HVAC license tests sizing tables, support spacing, and the leak/pressure-test procedure.

   • Sizing fuel-gas piping — Tables 402.4

     IFGC Table 402.4(1)+ gives the maximum CFH (cubic feet per hour) that various pipe sizes can deliver at given pipe lengths and pressure drops. Two pressure ranges: LOW PRESSURE systems (≤2 psi, typical residential) — pressure drop budget 0.5 in. WC; ELEVATED PRESSURE (2 psi inlet at meter, regulated down at appliance) — used in larger residential and commercial. Procedure: (1) determine total CFH demand (sum each appliance's BTU/hr ÷ 1,000 for natural gas; ÷ 2,500 for propane). (2) measure the LONGEST run from meter to farthest appliance (developed length, not straight-line). (3) look up the smallest pipe size that delivers required CFH at that length. APPLY THE LONGEST-RUN LENGTH TO ALL BRANCHES — this is the conservative simple-sizing method. The exam tests reading the table accurately; bring your IFGC code book and tab Table 402.4.

     Reference: IFGC Section 402 (Sizing of Gas Piping)

   • Support spacing for gas piping

     IFGC 415.1: piping support spacing depends on size and type. STEEL PIPE: 1/2 inch — 6 ft; 3/4 to 1 inch — 8 ft; 1-1/4 inch and larger — 10 ft horizontal; vertical runs — at every floor or 15 ft, whichever is less. CSST (corrugated stainless steel tubing) has different spacing per the manufacturer (typically 4-6 ft horizontal). Pipe must not contact ELECTRICAL CONDUIT or EQUIPMENT GROUND, must be supported in a way that allows for thermal expansion, and must not be supported by other piping (no tying gas to plumbing). Through-floor and through-wall penetrations require sleeves and proper sealing per the code.

     Reference: IFGC Section 415 (Piping Support)

   • Pressure test for new and altered gas systems

     Before activation, new gas piping must be pressure-tested. IFGC 406.4: test pressure must be at least 1.5 × max working pressure but NOT LESS THAN 3 PSI for low-pressure systems. Test medium: AIR or INERT GAS — never the fuel gas itself, never water. Test duration: at least 10 MINUTES per IFGC, but many AHJs require 30+ minutes for larger systems. Measure with a calibrated gauge at the test pressure range; the gauge must show NO PRESSURE DROP over the duration. If a drop occurs, locate leaks with soap solution (NOT a flame). Document the test on the inspection report — many states require an inspector witness for the pressure test before allowing gas-on.

   Practice questions (1)

   1. 1. A new residential gas system has a maximum working pressure of 0.5 psi. Per IFGC, what is the minimum pressure test pressure?

      • A.0.75 psi (1.5 × working pressure)
      • B.3 psi✓ correct
      • C.10 psi
      • D.15 psi

      IFGC 406.4 requires pressure test at the GREATER of 1.5 × max working pressure OR 3 psi. 1.5 × 0.5 = 0.75 psi, which is below the 3 psi floor — so 3 psi is the required minimum test pressure. Simply taking 1.5 × max working pressure (option A) misses the 3 psi floor. 10 psi and 15 psi are above the IFGC minimum but not required (some state amendments do require higher; check local AHJ).

4. 04Electrical for HVAC + IMC fundamentals

   ~75min

   HVAC technicians must understand basic motor branch circuits and low-voltage control wiring. The IMC governs the mechanical side: combustion air, venting, condensate disposal, and equipment clearances.

   • Motor branch circuits — NEC 430 basics

     NEC Article 430 governs motor circuit sizing. Key concept: motor BRANCH-CIRCUIT short-circuit and ground-fault protection (the breaker) is sized at 125-250% of the motor's full-load amps (FLA) — typically 175% for inverse-time breakers — to allow for STARTING CURRENT (which is 6-8× FLA for a few cycles). This is HIGHER than the conductor ampacity protection because the breaker is protecting the CIRCUIT against shorts, not the motor itself. The motor itself is protected by an OVERLOAD device (typically the starter's heater or thermal cutout) sized at 115-125% of FLA. So the breaker is 175% but the overload is 115% — different jobs, different sizes. Most HVAC equipment ships with a NAMEPLATE specifying min circuit ampacity (MCA) and max overcurrent protection (MOP) — install per nameplate.

     Reference: NEC 2023 Article 430 (Motors) + 440 (HVAC Equipment)

   • Low-voltage controls — 24V thermostat wiring

     Standard residential HVAC uses 24 VAC for control. Color codes: R = 24V hot (from transformer), C = 24V common (return), W = heat call, Y = cool call (compressor + condenser fan), G = blower (fan), O/B = reversing valve on heat pumps (O = energized in cool, B = energized in heat — system-specific). Modern systems add additional terminals: W2 (second-stage heat), Y2 (second-stage cool), Aux (auxiliary heat), E (emergency heat), and accessories like dehumidifier, humidifier, ERV controls. The exam tests: which terminal calls what; how a thermostat without a C-wire creates problems with smart thermostats; and basic short/open troubleshooting. R-to-C 24VAC reading at the thermostat means transformer is good; no reading means upstream issue.

   • IMC combustion air + venting

     IMC Chapter 7 governs combustion air. A FUEL-BURNING APPLIANCE in a confined space (volume < 50 cubic ft per 1,000 BTU/hr of all appliances combined) requires DEDICATED combustion air — typically two openings: one within 12 inches of the floor, one within 12 inches of the ceiling, each sized at 1 sq inch per 4,000 BTU/hr (when using outdoor air through a vertical duct), or 1 sq inch per 2,000 BTU/hr horizontal duct, or 1 sq inch per 1,000 BTU/hr if using indoor air only. IMC Chapter 8 covers VENTING: B-vent for atmospheric draft Category I appliances; PVC for Category IV condensing units (per the manufacturer's listing); minimum termination clearances from openings (typically 12-48 inches depending on category). Carbon monoxide alarms required adjacent to bedrooms in dwellings with fuel-burning appliances.

     Reference: IMC Chapter 7 (Combustion Air) + Chapter 8 (Chimneys and Vents)

   Practice questions (2)

   1. 1. A condensing unit nameplate shows MCA 22.5 A and MOP 35 A. What size breaker is allowed?

      • A.A 20 A breaker
      • B.A 30 A or 35 A breaker✓ correct
      • C.Any breaker over 22.5 A
      • D.Exactly 35 A

      MCA (Min Circuit Ampacity) is the minimum conductor ampacity — wires must be sized for at least 22.5 A. MOP (Max Overcurrent Protection) is the LARGEST breaker the manufacturer allows — the breaker can be smaller but never larger than 35 A. Standard sizes between MCA and MOP are 25, 30, 35 — pick a standard size in that range. A 20 A breaker is below MCA and would trip on inrush. "Any breaker over 22.5 A" misses the MOP cap. "Exactly 35 A" reads MOP as a requirement instead of a ceiling.

   2. 2. A 100,000 BTU/hr atmospheric-draft gas furnace is installed in a small mechanical closet. Without dedicated combustion-air openings to outdoors, the closet must contain at least how much volume to qualify as an unconfined space?

      • A.5,000 cubic feet✓ correct
      • B.10,000 cubic feet
      • C.50 cubic feet
      • D.100 cubic feet

      IMC defines a confined space as having less than 50 cubic feet per 1,000 BTU/hr of all appliances. For a 100,000 BTU/hr furnace, the unconfined-space minimum volume is 50 × 100 = 5,000 cubic feet — the closet must be at least that big. Below that volume, dedicated combustion air openings are required. 50 cubic feet (option C) confuses the per-1,000-BTU rate with the total volume; 100 cubic feet (D) is implausibly tiny.

5. 05Business + law — the section that sinks first-time candidates

   ~60min

   Most states bundle a business-and-law section (~25-50 questions) covering contracts, lien rights, tax basics, OSHA, workers' comp, and state-specific HVAC license law. It is closed- or limited-open-book and frequently underestimated.

   • State HVAC license law — the test that varies most

     Each state defines: who may pull permits (typically the licensed contractor only), the LICENSE TIERS (master, journeyman, apprentice; some states use Class I / II / III), CONTINUING EDUCATION HOURS required per renewal cycle, MINIMUM EXPERIENCE BEFORE EXAM (typically 4 years for journeyman, 4-8 years + journeyman tenure for master/contractor), INSURANCE + BONDING minimums (typically GL $300K-$1M, workers' comp, sometimes a surety bond $5K-$25K), and the RECIPROCITY agreements with nearby states. Read your state board's License Law SECTION BY SECTION and tab anything mentioning a specific dollar figure, time period, or hour count — those are the most tested. NEVER assume the rules from a neighboring state apply.

   • Contracts, mechanic's liens, and home-improvement statutes

     Most states require WRITTEN CONTRACTS for residential work over a threshold (often $1,000 or $5,000). Required content: scope of work, total price, payment schedule, license number, right-to-cancel notice (typically 3 days for residential per FTC Cooling Off Rule). MECHANIC'S LIEN procedure: Notice of Commencement filed before work begins; Notice to Owner sent within X days of starting (10-45 days, state-specific); claim of lien filed within X months after final furnishing of labor or materials (usually 60-120 days); foreclosure suit within X months of lien filing (typically 12 months). Failure to comply with notice rules waives lien rights. Construction contracts also typically require workers' comp documentation and OSHA poster compliance.

   Practice questions (1)

   1. 1. A residential homeowner signs an HVAC replacement contract at their home for $8,500. Per the federal FTC Cooling Off Rule, the homeowner has the right to cancel:

      • A.No right to cancel — contract is binding once signed
      • B.Within 24 hours
      • C.Within 3 business days✓ correct
      • D.Within 30 days

      The FTC Cooling Off Rule (16 CFR Part 429) gives consumers a right to cancel within 3 BUSINESS DAYS for sales of $25 or more made at the consumer's home or temporary location. The contractor must provide TWO copies of the cancellation notice. This rule is federal and applies regardless of state. Failure to provide the notice extends the cancellation right indefinitely, exposing the contractor to refund liability years later. State HVAC contracts of this size always require additional written terms — the FTC rule is on top of state law, not in lieu of it.

External resources

• Official
  ICC IMC + IFGC — Model Codes ↗

  International Code Council's online code library. Read-only access to current and prior editions of IMC and IFGC. Confirm which EDITION your state has adopted before studying — a 3-year-old edition is common.

• Official
  ACCA — Manuals J / D / S Standards ↗

  Air Conditioning Contractors of America publishes the load-calculation (Manual J), duct-design (Manual D), and equipment-selection (Manual S) standards referenced by IECC and IRC. State exams test the principles; the manuals themselves are the source of truth.

• Third-party
  NATE — State HVAC Licensing Requirements Map ↗

  NATE maintains a state-by-state map of HVAC licensing requirements: which states license contractors, journeymen, or technicians; which require state exam vs. local; reciprocity agreements; and links to each state board. Useful for picking the right state to credential in.