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Mississippi Residential HVAC Practice Exam

What This Practice Exam Covers

The Mississippi Residential HVAC licensing exam is 80 questions. You have 240 minutes to finish it. Passing requires a 70% — that's 56 correct answers out of 80.

This practice site gives you two ways to prepare:

Free practice exam: 10 questions per attempt, pulled from a limited pool. You can retake it as many times as you want. It's a good way to get a feel for question style and pacing before you commit to more.

Full practice exam (paid): 80 questions, 240-minute time limit — same format as the real thing. Questions are drawn from a pool of 552+ items, so every attempt pulls a different mix. You won't see the same exam twice. Every question ties directly to the official exam topic list, so you're drilling what actually shows up on test day, not filler material.

Start with the free exam. If your score concerns you, the full exam pool gives you the volume of practice you need to close the gap.

What You'll Be Tested On

The exam covers 19 topics. Here's what each one actually demands from you.

Ducts (14 items) — The heaviest topic on the exam. Expect questions on rectangular duct gauge selection, reinforcement schedules, and pressure classifications per SMACNA standards. You'll need to know round and oval duct wall thickness requirements, longitudinal vs. spiral seam differences, and how transverse joints must be made. Duct sealing, leakage classes, and which sealant types are acceptable are tested. Flexible duct length limits and installation rules show up here too.

Heating and Cooling Principles (6 items) — Know the three heat transfer modes: conduction, convection, and radiation. Understand sensible vs. latent heat and be able to apply them. The refrigeration cycle — compression, condensing, metering, evaporation — will appear in both conceptual and applied questions. R-value, U-value, K-value, and C-value are all fair game.

Load Calculations (6 items) — This topic requires math. You'll work with heating temperature difference (HTD), cooling temperature difference (CTD), and indoor/outdoor design conditions. Expect to calculate heat transfer multipliers (HTM) for walls, ceilings, floors, windows, and doors. Fenestration loads — windows, skylights, glass doors — are tested separately from opaque panel loads. Infiltration estimation using ACH tables or the component leakage area method also appears. Manual J (8th ed.) is the source document.

A/C and Heat Pump Equipment (6 items) — Know compressor types: reciprocating, rotary, scroll, hermetic, and semi-hermetic. Metering devices — capillary tube, TXV, fixed-orifice/piston, and EEV — and how each controls refrigerant flow. Heat pump reversing valve operation is tested, including which direction refrigerant flows in heating vs. cooling mode. Also expect questions on accumulators, filter-driers, sight glasses, and ductless/VRF equipment.

Furnaces and Heaters (5 items) — Gas furnace ignition systems: standing pilot, intermittent pilot, direct-spark, hot-surface ignition. Safety controls — high-limit switch, rollout switch, pressure switch, flame rectification — are tested with enough detail that you need to know what each one does and when it trips. Oil-fired furnace components, combustion efficiency testing (CO₂, stack temperature, draft, smoke), and electric resistance heating are all included.

Fuel Gas (5 items) — Gas piping materials: steel, copper, CSST, and polyethylene. Pipe sizing methods — longest length, branch length, and hybrid pressure — using code tables per the 2018 IFGC. Allowable pressure drop values and CSST bonding requirements come up. Know the difference between the methods; questions often hinge on which method applies in a given scenario.

Piping (5 items) — Overlaps with fuel gas but also covers hydronic piping: copper, PEX, CPVC, steel. Pressure testing, leak detection, purging, shutoff valves, and pressure regulators. CSST bonding is tested here as well as in Fuel Gas.

Refrigerants (4 items) — CFC, HCFC, HFC, HFO classifications. Ozone depletion potential (ODP) and global warming potential (GWP). EPA Section 608 certification requirements and refrigerant recovery rules. ASHRAE Standard 34 safety classifications — toxicity and flammability. Cylinder color codes and the ASHRAE numbering system.

Controls (4 items) — Thermostat types: bimetal, thermistor, mercury switch, millivolt. Heat and cooling anticipators. Low-voltage, line-voltage, and millivolt system differences. Oil burner primary controls, cad cell and stack-mounted flame detection, and limit controls including aquastat and low water cutoff.

LP Gas (4 items) — LP piping materials, sizing tables, pressure regulators (single-stage vs. two-stage), burial depth, support intervals, and pressure testing procedures. Know combustion properties that affect burner operation.

Insulation (3 items) — Duct insulation R-value requirements for attics, crawl spaces, and unconditioned basements. Flame spread and smoke-developed index limits for duct coverings per IMC. Vapor retarder requirements on externally insulated cooling ducts. Duct insulation labeling requirements.

Hangers and Supports (3 items) — Hanger spacing for rectangular, round, and flat oval duct. Upper attachment methods: concrete inserts, powder-actuated fasteners, beam clamps, welded studs. Minimum hanger and strap sizes based on duct perimeter. Trapeze hanger load calculations.

Chimneys, Flues and Vents (3 items) — Appliance venting categories I through IV and when each applies. Vent and chimney sizing using code tables for single and multiple appliances. Vent connector slope, clearances, length limits, and materials. Chimney termination height requirements.

Combustion Air (3 items) — Indoor combustion air volume requirements: standard method and known air-infiltration-rate method. Outdoor combustion air: two-permanent-openings vs. one-permanent-opening methods. Opening sizing and minimum dimensions. Mechanical combustion air supply and appliance interlock requirements.

Ventilation and Exhausts (3 items) — Clothes dryer exhaust duct length limits. Exhaust discharge location and minimum separation distances. Commercial kitchen hood types (Type I and Type II). Minimum mechanical ventilation rates by occupancy. MERV ratings for filtration.

Safety (2 items) — PPE selection. Fall protection systems: guardrail, safety net, personal fall arrest. Ladder safety. Confined space entry procedures. Hazardous substance exposure limits.

Fuel Oil (2 items) — Fuel oil grades, flash point, pour point, heat content. Storage tank types and installation. Oil burner nozzle spray patterns, angles, and flow rates. Fuel oil pump testing: pressure, cutoff, and vacuum tests.

Testing, Adjusting and Balancing (1 item) — Airflow measurement instruments: anemometers, pitot tubes, flow hoods, manometers. Duct leakage testing using a duct blaster (cfm25). Blower door testing (ACH50, cfm50). Air velocity calculation using the velocity pressure formula.

Sound, Vibration and Seismic Control (1 item) — Vibration isolation for HVAC equipment. Flexible connections at fans to isolate vibration from ductwork. Cross-breaking of sheet metal panels to reduce oil-canning. Seismic restraint requirements for mechanical system supports.

Worked Sample Questions

Question 1 — Ducts

An 8" round duct carries 250 CFM. What is the approximate velocity?

• A. 500 FPM
• B. 900 FPM
• C. 400 FPM
• D. 700 FPM

Correct Answer: D — 700 FPM

Convert the 8" diameter to feet: 8 ÷ 12 = 0.667 ft. Radius = 0.333 ft. Area = π × (0.333)² ≈ 0.349 ft². Divide CFM by area: 250 ÷ 0.349 ≈ 716 FPM, which rounds to 700 FPM. This is a straightforward velocity formula question. The trap is forgetting to convert inches to feet before calculating area — candidates who skip that step land on a nonsense answer.

Question 2 — Heating and Cooling Principles

Wet bulb temperature represents:

• A. Dry temperature
• B. Dew point
• C. Enthalpy and moisture
• D. Barometric pressure

Correct Answer: C — Enthalpy and moisture

Wet bulb temperature reflects both the heat content (enthalpy) and moisture content of air simultaneously. It's not the same as dew point (that's the temperature at which moisture condenses). It's not dry-bulb temperature (no moisture consideration) and has nothing to do with barometric pressure. On a psychrometric chart, wet bulb lines run diagonally — a key visual to memorize.

Source: Chapter 27, Air Movement and Measurement, Reading a Psychrometric Chart

Question 3 — Load Calculations

What is the sensible cooling load through the net exposed wall? (Gross wall = 22 ft × 8 ft; glass = 40 sq ft; no door)

• A. 588 Btuh
• B. 704 Btuh
• C. 1,088 Btuh
• D. 544 Btuh

Correct Answer: D — 544 Btuh

Gross wall area = 22 × 8 = 176 sq ft. Subtract glass: 176 − 40 = 136 sq ft net wall. Apply the heat transfer multiplier: 136 × 4.0 = 544 Btuh. The most common mistake here is using gross area instead of net area — forgetting to subtract window and door openings before multiplying by the HTM. Always find net area first.

Source: ACCA Manual J (8th ed.) — Section 5, Component Cooling Loads

How to Read Your Score

Passing is 70%. On the full practice exam, that means 56 out of 80.

Your first attempt is a diagnostic, not a verdict. Most people score lower than they expect on attempt one — that's normal and useful. A low score on a specific topic cluster tells you exactly where to put your study time. A low score across the board tells you to go back to fundamentals before retaking.

If you're scoring 75% or higher consistently across multiple attempts, you're in solid shape. If you're hovering between 65–74%, you're close but not ready — one bad section on the real exam can pull you under the line. Scoring below 65% means there are topic areas where you're guessing, and guessing is a liability on an 80-question exam with no partial credit.

Use the topic breakdown after each attempt. If you're losing points on Load Calculations or Ducts — the two heaviest topics — that's where to focus first. Those 20 combined items alone account for 25% of your total score.

Where Candidates Lose Points

Ducts (14 items): This section alone can make or break your exam. Candidates lose points by confusing pressure classifications and applying the wrong gauge, or mixing up leakage class requirements. Read question stems carefully — "rectangular" vs. "round" duct changes the answer.

Load Calculations (6 items): The most common mistake is using gross wall area instead of net area. The second most common is mixing up HTD and CTD — applying a heating multiplier to a cooling question. Slow down on these and show your work mentally before committing to an answer.

Fuel Gas and Piping (10 combined items): Candidates lose points by using the wrong sizing method or wrong table. The longest length method and branch length method produce different answers from the same pipe system. Know which one to use and when per the 2018 IFGC.

Refrigerants (4 items): Misidentifying refrigerant classifications — confusing HFC with HCFC, or getting ODP vs. GWP backwards — is a consistent point loss. Memorize the classification groups and their environmental profiles.

Controls (4 items): Thermostat anticipator questions trip people up. Knowing that the heating anticipator is in series and the cooling anticipator is in parallel is the kind of detail that separates a passing score from a failing one.

Time management: At 240 minutes for 80 questions, you have 3 minutes per question. Don't spend 8 minutes on one calculation and rush the rest. Flag it and move on.

Exam Quick Facts