Exam Cheat Sheet · Quick Reference
New Jersey Master HVACR Contractor Exam
New Jersey · 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
50
Passing score
70%
Exam time
130 min
Administered by
PSI Services Contractor
Format
Reference materials allowed
New Jersey State Portion 50 questions
Electrical Knowledge, Motors, and Controls
7 Q · 14%
Ohm's Law and electrical formula calculations (voltage, current, resistance, power)Series, parallel, and combination circuit analysisSingle-phase and three-phase AC motor types and starting methodsMotor capacitors (start and run): selection, testing, and replacementMotor nameplate data interpretation and full-load/locked-rotor current tablesMotor branch-circuit protection, overload devices, and NEC sizing requirementsElectrical control devices: switches, relays, contactors, and solenoidsThermostats and pressure controls: range, differential, cut-in/cut-out settings
Piping - Refrigeration, Hydronic, Steam, Process
7 Q · 14%
Heating and Cooling Principles, Theory, and Equipment
8 Q · 16%
Compression refrigeration cycle components and operation (compressor, condenser, metering device, evaporator)Types and construction of compressors (reciprocating, rotary, scroll, hermetic, semi-hermetic)Gas-fired heating systems: combustion principles, burner types, and furnace operationGas furnace efficiency ratings, venting categories, and ignition systemsOil-fired heating systems: fuel oil properties, combustion testing, and burner componentsElectric heating systems: resistance heating principles, element types, and system applicationsAir-source and geothermal heat pump operation, components, and efficiency ratingsAbsorption and evaporative cooling system principles and components
Refrigerants and Refrigeration
8 Q · 16%
Fuel and LP Gas
5 Q · 10%
Combustion Air, Chimneys, Flues and Vents
5 Q · 10%
Ducts, Ventilation and Exhaust
5 Q · 10%
Load Calculations
5 Q · 10%
Heating and cooling design temperature selection (indoor/outdoor design conditions, HTD and CTD)Thermal resistance and transmittance values (R-value, U-value, C-value, K-value) for building componentsFenestration load calculations (windows, glass doors, skylights — heating and cooling HTM values, solar heat gain, shading by overhangs and internal/external devices)Opaque panel load calculations (walls, ceilings, floors, doors — U-values, CLTD, heating and cooling HTM values)Infiltration load estimation methods (ACH table method, component leakage area method, blower door method)Duct system load calculations (conduction and leakage losses/gains, duct location and insulation factors)Ventilation load calculations (sensible and latent loads, heat recovery equipment adjustments)Internal, occupant, and supplemental loads (appliances, occupants, blower heat, humidification, hot water piping)
Key Distinctions
Pictorial wiring diagramvsLadder diagram
A pictorial diagram shows all device connections plus the approximate physical location of devices in the unit (and may show wire colors), while a ladder diagram shows the order of component operation using horizontal rungs between two vertical power lines.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 18 - Electrical Troubleshooting Fundamentals, Page 369 (Section 18.2.2) (20th ed.: Chapter 16, Section 16.1.1)K-value (thermal conductivity)vsC-value (thermal conductance)
K-value is based on a standardized one-inch thickness of material, while C-value is based on the material's actual measured thickness.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 32 - Heating and Cooling Loads, Page 717 (20th ed.: Page 986)ACR tubing sizingvsCopper water tubing sizing
ACR tubing size is designated by its actual outside diameter, while copper water tubing nominal size equals the outside diameter minus 1/8″.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 5 - Working with Tubing and Piping, Page 71 (Section 5.1.1) (20th ed.: Chapter 8, Section 8.1.1)Hard lockoutvsSoft lockout
A hard lockout shuts the system down for an unspecified time after a failed trial for ignition and requires a service call or power interruption to reset, while a soft lockout automatically retries after a waiting period.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 33 - Gas-Fired Heating Systems, Page 770 (20th ed.: Page 1129)Category III gas furnacevsCategory IV gas furnace
Category III is positive-pressure, noncondensing and typically vented with stainless steel pipe, while Category IV is positive-pressure, condensing (flue gas below 140°F/60°C, below its dew point) with a secondary heat exchanger and PVC vent piping.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 776 (Section 33.8)Shell-and-coil water-cooled condenservsShell-and-tube water-cooled condenser
The coiled water tubing of a shell-and-coil condenser cannot be accessed for mechanical cleaning and must be cleaned with chemicals, while a shell-and-tube condenser has removable end caps that allow mechanical cleaning of its straight water tubes.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 44 - Commercial Evaporators, Condensers, and Other Heat Exchangers, Page 1069 (Section 44.2.2) (20th ed.: Page 537)Subcooling charging methodvsSuperheat charging method
The subcooling method is generally used to check the charge on systems with thermostatic expansion valves, while the superheat method is used on systems with fixed orifice metering devices such as capillary tubes.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 12 - Working with Refrigerants, Page 221 (20th ed.: Page 236)Hot-surface ignition (HSI) flame sensingvsDirect spark ignition (DSI) flame sensing
HSI systems require a separate flame rod to prove flame by flame rectification because the glow coil only ignites and cannot sense, while DSI systems can use the high-voltage electrode for both ignition and sensing.
Modern Refrigeration and Air Conditioning (22nd ed.), Pages 765-766 (Section 33.5.4)Duct leakage tested before air handler installedvsDuct leakage tested with air handler installed
Per the IECC, maximum leakage is 3 cfm per 100 ft² of conditioned space when tested before the air handler is installed and 4 cfm per 100 ft² when tested with the air handler installed.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 31 - Ventilation System Service, Page 703 (Section 31.1.5) (20th ed.: Page 793)Gas appliance in a private garagevsGas appliance in a public garage
Per IFGC 2021 Section 305.5, appliances in private garages require a minimum clearance of 6 feet above the floor while public garages require 8 feet; an exception applies where the appliance is protected from motor vehicle impact and installed per Section 305.3.
IFGC 2021 Section 305.5Three-phase motor startingvsSingle-phase motor starting
A three-phase supply is already phase-split (each phase peaks at a different time), so the motor develops starting torque without start windings or capacitors, which single-phase motors need for phase splitting.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 16 - Electric Motors, Page 308 (Section 16.2.2) (20th ed.: Chapter 15, Section 15.2.2)Heating load infiltrationvsCooling load infiltration
Heating load calculations consider only the sensible heat loss from infiltration, while cooling load calculations must include both sensible and latent heat gains from infiltration.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 32 - Heating and Cooling Loads, Page 733 (20th ed.: Page 1004)Low-temperature evaporator fin spacingvsMedium/high-temperature evaporator fin spacing
Low-temperature evaporators have fins spaced further apart than medium- and high-temperature evaporators so air can still flow around the fins when some frost has built up.
Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 44 - Commercial Evaporators, Condensers, and Other Heat Exchangers, Page 1050 (20th ed.: Page 521)Apparent power (VA)vsTrue power (watts)
Apparent power is calculated as I × E, while true power is the wattmeter reading; their ratio ×100 is the power factor, which falls below 100% when inductive or capacitive components shift voltage and current out of phase.
Modern Refrigeration and Air Conditioning (22nd ed.), Page 275 (Section 14.1.3)Key Terms
Low-heat appliance (residential appliance) IFGC 2021 Section 202, Appliance Type definitions
Per IFGC 2021 Section 202, any appliance in which the products of combustion at the point of entrance to the flue under normal operating conditions have a temperature of 1,000°F (538°C) or less.
Ventilated metal thimble (single-wall metal vent through a combustible exterior wall) IFGC 2021 Section 503.7.7
Per IFGC 2021 Section 503.7.7 Item 1, for listed appliances with draft hoods the thimble shall be not less than 4 inches larger in diameter than the metal pipe; the 2-inch reduction is permitted only where there is a run of not less than 6 feet of metal pipe in the open between the draft hood outlet and the thimble.
Spray polyurethane foam duct insulation (attics and crawl spaces) IMC 2021 Section 604.3 Exception
Per IMC 2021 Section 604.3 Exception, foam applied to the exterior of ducts in attics and crawl spaces shall have a flame spread index not greater than 25 and a smoke-developed index not greater than 450 when tested to ASTM E84 or UL 723 — a relaxed smoke limit compared with the standard 50 for other coverings and linings.
Domestic clothes dryer exhaust duct length IMC 2021 Section 504.9.4.1 and Table 504.9.4.1
Per IMC 2021 Section 504.9.4.1 and Table 504.9.4.1, the maximum exhaust duct length is 35 feet measured from the transition duct connection to the outlet terminal, reduced by the equivalent length of each fitting (a 4-inch radius mitered 90-degree elbow counts as 5 feet).
Default occupant density, office space IMC 2021 Table 403.3.1.1
Per IMC 2021 Table 403.3.1.1, office spaces use a default occupant density of 5 occupants per 1,000 square feet for ventilation design.
Interior room ventilated through an adjoining room IMC 2021 Section 402.3
Per IMC 2021 Section 402.3, the unobstructed opening to the adjoining room shall be not less than 8 percent of the interior room's floor area and not less than 25 square feet.
PTC relay (positive temperature coefficient) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 346 (Section 17.5) (20th ed.: Chapter 16, Section 16.3.5 — Positive Temperature Coefficient Relays)
A starting device wired in parallel with the run capacitor whose resistance is low (3 Ω to 12 Ω) when cool, so starting current takes that path, then rises dramatically (10 kΩ to 20 kΩ) as it heats to its set point, forcing current through the run capacitor.
Potential relay Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 339 ("Potential Relays") (20th ed.: Chapter 16, Section 16.3.5 — Potential Relays)
A motor starting relay that actuates on the counter electromotive force (cemf) induced in the start winding as the motor approaches rated speed, energizing at pickup voltage (about three-fourths of normal speed) to open its normally closed contacts and drop out the start capacitor.
Current relay terminals L, M, S Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 339 (Section 17.4.5) (20th ed.: Chapter 16, Section 16.3.5 — Current Relays)
L is line voltage, M is the main (run) winding and S is the start winding; a normally open contact is between L and S and the relay coil is between L and M, with the ungrounded (hot) wire landing on L.
Multipurpose fuse Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 347 (Section 17.5.1) (20th ed.: Chapter 16, Section 16.4.1)
A fuse combining fast-acting and time-delay advantages: it will not blow on small short-duration overloads such as motor starting, but blows immediately on an extremely high overload (over 500% of the maximum current rating).
High-pressure motor control Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 334 ("High-Pressure Motor Controls") (20th ed.: Chapter 16, Section 16.3.4 — High-Pressure Motor Controls)
A safety control usually set to cut out at 20% above normal head pressure, protecting the compressor from high pressure and temperature and the motor from overheating and overloading.
Differential adjustment (low-pressure motor control) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 17 - Electrical Control Systems, Page 333 (Section 17.4.4) (20th ed.: Chapter 16, Section 16.3.4 — Low-Pressure Motor Controls)
An adjustment that affects only the cut-out setting; turning the screw clockwise (in) raises the cut-out pressure by increasing spring tension, leaving the cut-in setting unchanged.
Sequencer (electric furnace) Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 35 - Electric Heating Systems, Page 834 (20th ed.: Pages 1196 and 1205)
A device that closes and opens its contacts on a time delay to energize heating elements one after another, typically about 30 seconds apart, minimizing the furnace's initial current draw.
Overfiring Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 34 - Oil-Fired Heating Systems, Page 795 (Section 34.3.2) (20th ed.: Page 1154)
A condition in which a heating system creates too much heat — often from installing a burner nozzle of higher capacity than the original — so the heat exchanger cannot absorb it all and the excess escapes up the flue, raising stack temperature.
Refrigerant distributor Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 45 - Commercial Metering Devices and Valves, Page 1088 (Section 45.1.4) (20th ed.: Pages 490-491)
A device at the metering device outlet that splits refrigerant into several shorter parallel paths in the evaporator, reducing pressure drop across the evaporator and giving more consistent surface temperature.
Refrigerant quality Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 51 - Understanding Heat Loads and System Thermodynamics, Page 1273 (20th ed.: Page 1372)
On a pressure-enthalpy diagram, the fraction of the refrigerant mass that is in the vapor state — a 10% quality means 10% vapor and 90% liquid.
cfm50 / cfm25 Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 31 - Ventilation System Service, Page 702 (20th ed.: Page 791)
cfm50 is the airflow through a blower door fan with indoor pressure held at −50 Pa WRT outdoors (used to calculate ACH50); cfm25 is the airflow needed to hold sealed ductwork at +25 Pa WRT the conditioned space during a duct leakage test.
HTD and CTD (Manual J) ACCA Manual J Residential Load Calculation (Abridged), Sections 3-6, 3-7 and 6-3
Per Manual J Sections 3-6 and 6-3, with indoor design targets of 70°F dry-bulb heating and 75°F dry-bulb/50% RH cooling, HTD = indoor heating dry-bulb − 99% outdoor value and CTD = 1% outdoor value − indoor cooling dry-bulb.
Net wall area Modern Refrigeration and Air Conditioning (22nd ed.), Chapter 32 - Heating and Cooling Loads, Page 725 (20th ed.: Pages 993–995)
Total wall area (perimeter × ceiling height) minus the combined area of windows and doors.
Formulas to Know
Ohm's law (current, resistance, voltage)
I = E ÷ R (also Amperes = Watts ÷ Volts); R = E ÷ I; E = I × R. Examples: 1500 W ÷ 120 V = 12.5 A; 240 V ÷ 8 A = 30 Ω; 240 V ÷ 10 A = 24 Ω; 10 A × 12 Ω = 120 V.Power (Watt's law) in watts
P = E × I (volts × amperes); when voltage and resistance are known, P = E² ÷ R. Examples: 20 A × 120 V = 2400 W; 15 A × 240 V = 3600 W; (240 V)² ÷ 20 Ω = 2880 W. Rearranged for current: I = P ÷ E (3600 W ÷ 240 V = 15 A; 3600 W ÷ 120 V = 30 A).Power factor
Apparent power = I × E (VA); true power = wattmeter reading; Power factor = (true power ÷ apparent power) × 100. Example: (2880 W ÷ 3600 VA) × 100 = 80%.Series circuit current and voltage drop
Total current equals the current in any other part of the circuit (IT = I1 = I2 = I3); total resistance is the sum of the resistances; I = E ÷ RT; voltage drop across a component = I × R and the individual drops sum to the applied voltage. Examples: 24 V ÷ 8 Ω = 3 A; (0.1+0.1+0.3+23.5) = 24 Ω, 120 V ÷ 24 Ω = 5 A, 5 A × 23.5 Ω = 117.5 V.Btu/hr to kilowatts for electric heat sizing
kW = Btu/hr ÷ 3,413. Example: 50,000 ÷ 3,413 = 14.65 kW minimum capacity.Coefficient of performance (COP) from a pressure-enthalpy diagram
COP = refrigeration effect ÷ heat of compression. Example: (179 − 116) ÷ (198 − 179) = 63 ÷ 19 = 3.32:1.Air changes per hour for a space
ACH = (airflow in cfm × 60 min) ÷ volume of room in cubic feet.Manual J ventilation loads on the cooling coil
Latent ventilation load = 0.68 × ACF × CFMvent × grains difference (example: 0.68 × 1.0 × 50 × 28 = 952 Btuh); sensible ventilation load is a separate line item = 1.1 × ACF × CFMvent × CTD (example: 1.1 × 1.0 × 50 × 18 = 990 Btuh).Manual J block infiltration heating load
Envelope infiltration Cfm = (ACH × above-grade volume) ÷ 60; add the fireplace adjustment Cfm; load = 1.1 × ACF × total Cfm × HTD. Example: (0.40 × 16,000)/60 = 106.7 + 12 = 118.7 Cfm; 1.1 × 1.0 × 118.7 × 60 ≈ 7,832 Btuh.Manual J wall heating load (and shade line)
Wall heating HTM = U × HTD and load = HTM × NET area (gross panel area − window and door area). Example: 0.090 × 55 = 4.95 Btuh/SqFt × (400 − 60 − 20) = 1,584 Btuh. Shade line Z = overhang length × shade-line multiplier; shaded glass height S = Z − Y (example: 2.0 × 1.6 = 3.2; 3.2 − 1.0 = 2.2 ft).