Exam Cheat Sheet · Quick Reference
Tennessee CMC-C Mechanical HVAC/Refrigeration Contractor
Tennessee · PSI Services Contractor
Verified, not estimated. Every figure below is drawn from the official exam structure we maintain — question counts, passing standard and topic weighting. Practice questions are grounded in the source law with statute citations. We omit any figure we can't verify rather than guess at it.
Total questions
100
Passing score
73%
Exam time
260 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
Tennessee State Portion 100 questions
Electrical Knowledge, Motors, and Controls
7 Q · 7%
Electrical KnowledgeMotorsControlsCircuit diagrams (pictorial and ladder)Ohm's Law and electrical formulas (watts, horsepower, kVA)Series and parallel circuit calculationsSingle-phase and three-phase powerMotor starting relays (current, potential, PTC, solid-state)Motor protection devices (fuses, circuit breakers, overload units, branch-circuit protective device ratings)Thermostats (types, wiring terminals, anticipators, diagnostics)Electrical test equipment (multimeter, ammeter, megohmmeter)
Piping - Refrigeration, Hydronic, Steam and Process
14 Q · 14%
Refrigeration PipingHydronic PipingSteam PipingProcess PipingTubing cutting, bending, and preparation techniquesFlared, soldered, brazed, and swaged tubing connectionsPipe and tubing materials selection (copper, steel, plastic)Refrigerant piping sizing and oil return considerationsHydronic piping joints and connection types by materialPipe support spacing and hanger requirementsFuel oil piping materials, joints, and installation requirementsBoiler piping connections, safety relief valves, and pressure vessels
Heating and Cooling Principles and Theory
10 Q · 10%
Heating PrinciplesCooling PrinciplesTheoryCompression refrigeration cycle components and operationGas laws and pressure-temperature relationshipsHeat transfer calculations (K-value, C-value, R-value, U-value)Heating and cooling load calculations (Manual J methodology)Heat pump operation and efficiency ratings (COP, SEER, HSPF)Psychrometrics and humidity measurementAbsorption and evaporative cooling system operationCombustion principles and efficiency measurement
Heating and Cooling Equipment and Components
10 Q · 10%
Heating EquipmentCooling EquipmentComponentsCompression Refrigeration Cycle FundamentalsCompressor Types and ConfigurationsMetering Device Types and OperationEvaporators and CondensersRefrigerant Flow and System ComponentsHeat Pump Operation and ComponentsHydronic System Components and DesignsCombustion Heating System Operation and Efficiency
Refrigerants and Refrigeration
10 Q · 10%
RefrigerantsRefrigerationRefrigeration system components and their functions (compressor, condenser, evaporator, metering device)Refrigerant classification and environmental properties (CFC, HCFC, HFC, HFO, HC, ODP, GWP)Refrigerant handling equipment (cylinders, gauge manifolds, service valves, vacuum pumps)Refrigerant recovery, recycling, and reclaiming proceduresEPA Section 608 certification requirements and Clean Air Act regulationsLeak detection methods and refrigerant charge verification (superheat and subcooling)Refrigerant flow components (filter-driers, sight glasses, liquid receivers, solenoid valves, pressure-regulating valves)IMC Chapter 11 refrigeration system classification, machinery room requirements, and refrigerant quantity limits
Fuel and LP Gas
10 Q · 10%
FuelLP GasGas piping materials, sizing, and pressure requirementsCombustion air requirements for gas-fired appliancesVenting systems for gas appliances (chimneys, vents, and connectors)LP gas storage, handling, and safety considerationsGas appliance installation, location, and clearance requirementsPressure testing and leak detection of gas piping systemsCombustion efficiency and flue gas analysis for gas-fired heating systemsFuel oil piping, storage, and oil-fired heating system components
Combustion Air, Chimneys, Flues and Vents
10 Q · 10%
Combustion AirChimneysFluesVentsVent connector materials, installation, and clearancesVenting system sizing methods for Category I appliancesAppliance venting categories and type-to-appliance matchingDraft hoods, draft controls, and barometric draft regulatorsVent and chimney termination height and location requirementsDirect-vent and mechanical draft system terminal clearancesCombustion air supply methods (indoor, outdoor, and combination)Safety inspection procedures for existing venting and combustion air systems
Ducts, Ventilation and Exhaust
14 Q · 14%
DuctsVentilationExhaustDuct pressure classification and material selectionDuct sealing requirements and leakage testingFire and smoke dampers in duct systemsDuct hangers, supports, and spacing requirementsPlenums and return air opening restrictionsExhaust outlet location and discharge clearancesOutdoor air intake location and protection requirementsDuct insulation and thermal load considerations
Load Calculation
5 Q · 5%
Indoor and outdoor design conditions (HTD, CTD, design temperatures, grains difference)Fenestration heating and cooling load calculations (HTM values, U-values, overhang adjustments, shading)Opaque panel heating and cooling load calculations (walls, ceilings, floors, doors, U-values, CLTD)Infiltration load estimation methods (ACH table method, component leakage area method, blower door method)Duct system load calculations (heat loss factors, sensible and latent gain factors, leakage and insulation adjustments)Internal load estimation (occupants, appliances, sensible and latent defaults)Ventilation load calculations (engineered ventilation, heat recovery equipment, sensible and latent loads)Block load vs. room load distinctions and Form J1 calculation procedures
Safety, Fire and Smoke Protection
10 Q · 10%
SafetyFire ProtectionSmoke ProtectionFire and smoke dampers (installation, ratings, and placement in duct systems)Lockout/tagout (LOTO) procedures for HVAC equipmentPersonal protective equipment (PPE) selection and useFlammable and combustible liquid storage and handling requirementsHazard assessment and safety data sheets (SDS)Plenum construction materials and flame/smoke spread ratingsExhaust ventilation for hazardous materials and flammable vaporsFire extinguisher types, classifications, and PASS method
Key Distinctions
Pictorial Wiring DiagramvsLadder Diagram
A pictorial diagram shows the approximate physical location of devices and wire colors within the unit, while a ladder diagram shows the order of component operation using horizontal rungs between two vertical power lines.
Chapter 16, Section 16.1.1Solid-State Relay (SSR)vsElectromagnetic Relay
An SSR uses electronic components (transistors, SCRs, triacs) with no physical movement for switching, while electromagnetic relays use mechanical contacts that physically open and close.
Chapter 16, Section 16.3.5 — Solid-State RelaysPTC Thermistor (cold state)vsPTC Thermistor (heated state)
When cool, a PTC thermistor has low resistance (3–12 Ω) providing a start-current path; once heated to set point, resistance rises dramatically (10–20 kΩ), forcing current through the run capacitor instead.
Chapter 16, Section 16.3.5 — Positive Temperature Coefficient RelaysHard LockoutvsSoft Lockout
A hard lockout shuts the furnace down for an unspecified time requiring a manual power interruption to reset, while a soft lockout automatically retries ignition after a waiting period.
Modern Refrigeration and Air Conditioning, Page 1129Building-Related Illness (BRI)vsSick Building Syndrome (SBS)
BRI involves a specifically diagnosable illness caused by airborne agents whose symptoms persist even after leaving the building, whereas SBS has no identifiable illness or specific cause and symptoms disappear when occupants leave.
Modern Refrigeration and Air Conditioning, Page 730K-value (Thermal Conductivity)vsC-value (Thermal Conductance)
K-value measures heat passing through a standardized one-inch thickness of material per square foot per hour per 1°F difference, while C-value measures thermal conductance based on the material's actual measured thickness.
Modern Refrigeration and Air Conditioning, Page 986ACR TubingvsCopper Water Tubing
ACR tubing is sized by its actual outside diameter, while copper water tubing nominal size equals the outside diameter minus 1/8 inch.
Modern Refrigeration And Air Conditioning, Chapter 8, Section 8.1.1Galvanized PipevsBlack Pipe
Galvanized pipe is coated with zinc for corrosion resistance and used primarily in water systems, while black pipe is less expensive and used for gas lines and non-water applications.
Modern Refrigeration And Air Conditioning, Chapter 8, Section 8.2.3Liquid Line Connection (recovery)vsDischarge Service Valve Connection (recovery)
Connecting to the liquid line during refrigerant recovery takes advantage of subcooled liquid refrigerant for faster recovery, while refrigerant at the discharge service valve is superheated high-pressure vapor making recovery slower.
Modern Refrigeration and Air Conditioning, Page 1500Vertical Suction Line RiservsHorizontal Suction Line Run
A vertical riser requires a smaller pipe diameter to maintain the higher oil-return velocity (1,000–1,500 fpm) needed against gravity, while horizontal runs require only 500–700 fpm and can use a larger diameter.
Modern Refrigeration and Air Conditioning, Page 1393Variable Volume Duct (upstream of VAV boxes) — Default Pressure ClassvsAll Other Duct — Default Pressure Class
When no pressure class is designated by the designer, variable volume duct upstream of VAV boxes defaults to 2 in. wg, while all other ducts default to 1 in. wg.
HVAC Duct Construction Standards, Page 1.1Duct Leakage Test (before air handler installed)vsDuct Leakage Test (with air handler installed)
Maximum permitted duct leakage is 3 cfm per 100 ft² of conditioned space when tested before the air handler is installed, versus 4 cfm per 100 ft² when tested with the air handler installed.
Modern Refrigeration and Air Conditioning, Page 793Key Terms
Velocity Pressure Modern Refrigeration and Air Conditioning, Page 710
The difference between total air pressure and static air pressure, measured by a pitot tube; total pressure equals static pressure plus velocity pressure.
Subcooling Modern Refrigeration and Air Conditioning, Page 68
The difference between a liquid refrigerant's condensing temperature at operating pressure and its actual measured temperature, indicating how far below its boiling point the liquid has been cooled.
Zeotropic Refrigerant Blend Fractionation Modern Refrigeration and Air Conditioning, Page 259
The separation of component refrigerants in a 400-series blend when charged as vapor (lowest boiling point component fills the system first), which is why zeotropic blends must always be liquid charged.
Differential (pressure/temperature control) Chapter 16, Section 16.2.2
The difference between a control's cut-out and cut-in values, representing the swing during which the system cycles on and off.
Receiver Pressure Regulator (ORD Valve) Modern Refrigeration and Air Conditioning, Page 586
A head-pressure control valve that bypasses hot-gas refrigerant from the compressor discharge to the liquid receiver when the pressure difference between them reaches approximately 20–30 psi, maintaining head pressure during cold weather operation.
cfm50 (Blower Door Measurement) Modern Refrigeration and Air Conditioning, Page 791
The measured airflow through a blower door fan when indoor pressure is held at −50 Pa with respect to outdoors, used to calculate air changes per hour at that pressure (ACH50).
cfm25 (Duct Leakage Measurement) Modern Refrigeration and Air Conditioning, Page 792
The airflow required to maintain ductwork pressurized to +25 Pa with respect to the conditioned space during a duct leakage test.
High-Pressure Motor Control Cut-Out Setting Chapter 16, Section 16.3.4 — High-Pressure Motor Controls
A safety control on commercial refrigeration units typically set to cut out at 20% above normal head pressure to protect the compressor from high pressure and high temperature.
Fire Extinguisher Rating Requirement (OSHA 1926.150) OSHA 1926.150(c)(1)(i)
Per OSHA 1926.150(c)(1)(i), a fire extinguisher rated not less than 2A shall be provided for each 3,000 square feet of protected building area on a construction site.
PVC Thermal Compensation Threshold (Type I) Plastic Pipe chapter, PVC Thermal Expansion section
Thermal compensation of a solvent-welded Type I PVC pipeline is not required when operating temperature extremes do not differ from installation temperature by more than plus or minus 30°F.
Gas Appliance Clearance in Private Garage (IFGC Section 305.5) International Fuel Gas Code 2021, Page 3-7 (Section 305.5)
Per IFGC Section 305.5, gas-fired appliances in private garages shall be installed with a minimum clearance of 6 feet above the floor (public garages require 8 feet).
Formulas to Know
Heating Temperature Difference (HTD)
HTD = Indoor design dry-bulb temp − Outdoor winter design dry-bulb tempCooling Temperature Difference (CTD)
CTD = Outdoor summer design dry-bulb temp − Indoor design dry-bulb tempFenestration / Opaque Panel Heat Loss
Heat Loss (Btu/hr) = U-value × Area (ft²) × HTDOpaque Panel Cooling Load (CLTD Method)
Cooling Load (Btu/hr) = U-value × Area (ft²) × CLTDInfiltration Load — ACH Method
Infiltration CFM = (Volume of space × ACH) ÷ 60; Sensible Load (Btu/hr) = CFM × 1.1 × ΔTVentilation Sensible Load
Sensible Load (Btu/hr) = CFM × 1.1 × (Outdoor dry-bulb − Indoor dry-bulb)Ventilation Latent Load
Latent Load (Btu/hr) = CFM × 0.68 × (Outdoor grains − Indoor grains)Subcooling
Subcooling (°F) = Saturation (condensing) temp at operating pressure − Actual liquid line tempSuperheat
Superheat (°F) = Actual suction line temp − Saturation (evaporating) temp at operating pressureOhm's Law / Watt's Law (electrical load calculations)
V = I × R; P (watts) = I × E; I = E ÷ R