HVAC Fundamentals
20%of exam
Electrical and Controls
20%of exam
Comfort and Airflow
20%of exam
Installation
20%of exam
Service
20%of exam
Quick Facts
- Credential
- Certified HVAC Professional (CHP-5)
- Required
- Pass all five exams
- Questions per exam
- 30
- Time per exam
- 60 minutes
- Format
- Closed book
- Result
- Pass/fail
- Exam spacing
- Up to six months apart
- Testing
- In person or live online
- Renewal
- Every two years
- CE renewal option
- 16 hours plus renewal fee
- Pathway share per exam
- 20% of all 150 questions
Refrigeration Cycle
Compress → Condense → Meter → Evaporate
Compressor raises pressureCondenser rejects heatMetering device drops pressureEvaporator absorbs heat
Superheat vs Subcooling
Superheat
- Suction-line vapor above saturation
- Line temperature minus saturation
- Use blend dew temperature
Subcooling
- Liquid-line refrigerant below saturation
- Saturation minus line temperature
- Use blend bubble temperature
Pair pressure and temperature locally
Fundamentals Exam Topics
- Safety
- 26.67%
- Tools
- 16.67%
- Science and heat transfer
- 20%
- Codes and regulations
- 20%
- Basic construction
- 16.67%
Safety and Tools
- Lockout/tagout
- Control hazardous energy during service
- Stored energy
- Relieve or restrain safely
- Electrical isolation
- Verify absence of voltage
- Safety data sheet
- Chemical hazards and protection
- Section 608
- Federal refrigerant technician credential
- Recovery machine
- Transfers refrigerant to recovery cylinder
- Tube reamer
- Removes burrs after cutting
- Tube bender
- Forms bends without kinking
- Construction plans
- Locate framing and service routes
Heat and Refrigeration
- Conduction
- Heat through molecular interactions
- Convection
- Heat carried by fluid motion
- Radiation
- Heat via electromagnetic waves
- One cooling ton
- 12,000 Btu/h
- Compressor
- Raises vapor pressure and temperature
- Condenser
- Rejects heat and condenses vapor
- Metering device
- Drops pressure and meters flow
- Evaporator
- Absorbs heat and boils refrigerant
- Pressure-temperature chart
- Converts pressure to saturation temperature
- Superheat
- Suction temperature − vapor saturation temperature
- Subcooling
- Liquid saturation temperature − liquid temperature
Conventional Thermostat Calls
Y cools, W warms, G blows
Y calls compressor in coolingW calls conventional heatG calls indoor fan
Series vs Parallel
Series
- One current path
- Same current through each load
- Resistances add
Parallel
- Multiple current paths
- Same voltage across branches
- Branch currents add
Series current, parallel voltage
Electrical Test Picker
- Measure control voltage→Rated voltmeter across test points(Energized work requires qualified personnel)
- Check motor current→Clamp one conductor(Energized work requires qualified personnel)
- Check winding resistance→Isolate energy sources and winding(Verify absence of voltage)
- Check capacitor value→Isolate, discharge safely, measure µF(Compare with marked tolerance)
- 24 VAC control supply missing→Trace transformer supply and fuse(Follow equipment schematic)
- Demand present, load idle→Check safeties and switching path(Follow sequence of operation)
Electrical Exam Topics
- Electrical science fundamentals
- 20%
- Basic electricity
- 20%
- Electrical troubleshooting
- 23.33%
- Controls
- 20%
- Wiring layouts
- 16.67%
Circuits and Metering
- Ohm’s law
- V = I × R
- Resistive power
- W = V × A
- AC frequency
- Cycles per second
- Series circuit
- Same current through loads
- Parallel circuit
- Same voltage across branches
- Voltmeter
- Measure across two points
- Clamp ammeter
- Clamp around one conductor
- Ohmmeter
- Isolate component and deenergize
- Schematic
- Shows electrical relationships
- Wiring diagram
- Identifies connection points
- Single-phase real power
- Watts = volts × amps × PF
- Power factor (PF)
- Real power ÷ apparent power
Motors and Controls
- Typical control transformer
- Steps line voltage to 24 VAC
- Contactor
- Coil switches load contacts
- Start capacitor
- Boosts starting torque
- Run capacitor
- Stays in motor run circuit
- PSC motor
- Permanent split capacitor motor
- ECM
- Electronically commutated motor
- R
- 24 VAC supply
- C
- Transformer secondary common
- Y
- Compressor call
- G
- Indoor fan call
- W
- Conventional heat call
- O/B
- Heat pump changeover signal
Sensible vs Latent
Sensible
- Changes dry-bulb temperature
- Humidity ratio stays constant
- Horizontal psychrometric chart path
Latent
- Associated with moisture phase change
- Cooling coil condenses water
- Humidity ratio falls during dehumidification
Total cooling combines both capacities
Airflow Test Picker
- Need register airflow→Use calibrated flow hood
- Need velocity-based duct airflow→Traverse duct and average velocities(Multiply by duct area)
- Need blower airflow estimate→Use external static and fan table(Match blower setting and taps)
- Suspect a restricted filter→Measure pressure drop across filter(Compare at known airflow)
- Need duct leakage measurement→Use calibrated duct leakage tester
- Room airflow misses design→Balance dampers and remeasure(Verify total system airflow)
Comfort and Airflow Exam Topics
- Comfort
- 23%
- Temperature and humidity measurements
- 27%
- Airflow
- 27%
- Air balancing
- 23%
Static Pressure vs Airflow
External static pressure
- Supply static minus return static
- Measure with manometer
- Use manufacturer test locations
Airflow
- Volume per unit time
- Measure outlet CFM with hood
- Estimate blower CFM with table
Match fan setting to measured static
Moist Air
- Dry-bulb
- Ordinary air temperature
- Wet-bulb
- Evaporatively cooled wick temperature
- Dew point
- Air’s saturation temperature upon cooling
- Relative humidity
- Percent of saturation vapor pressure
- Humidity ratio
- Water mass per dry-air mass
- Specific enthalpy
- Btu per pound dry air
- Sensible heat ratio
- Sensible capacity ÷ total capacity
- Condensation
- Surface colder than air’s dew point
- Sling psychrometer
- Measures dry-bulb and wet-bulb
- Mechanical ventilation
- Controlled outdoor air exchange
Airflow and Balancing
- CFM
- Cubic feet per minute
- Duct airflow
- Average FPM × area in ft²
- FPM
- Feet per minute
- Static pressure
- Duct pressure relative to reference
- Velocity pressure
- Pressure associated with air speed
- Total pressure
- Static plus velocity pressure
- External static pressure
- Supply static − return static
- Filter pressure drop
- Upstream static − downstream static
- Fan table
- Airflow from static and setting
- Balancing damper
- Adjusts airflow to design target
- Rectangular duct area
- Width (ft) × height (ft)
Sealed Circuit Sequence
Pressure-test, evacuate, verify decay, charge
Dry nitrogen for pressure testMicron gauge for evacuationIsolate pump for decayUse specified charge method
Pressure Test vs Evacuation
Positive pressure test
- Regulated dry nitrogen
- Checks joint and piping integrity
- Follow equipment test pressure
Evacuation
- Vacuum pump and micron gauge
- Removes air and moisture
- Check decay after isolating pump
Pressure-test before evacuation
Installation Check Picker
- Brazing refrigerant tubing→Use low-flow nitrogen purge
- Check line-set joints for leaks→Pressure-test with regulated dry nitrogen(Use equipment pressure limits)
- Pressure test passes→Relieve nitrogen pressure, then evacuate(Use pump and micron gauge)
- Target vacuum reached→Isolate pump and check decay(Apply manufacturer acceptance limits)
- Specified charge by mass→Use calibrated refrigerant scale
- Fixed orifice with charging chart→Check target superheat(Verify airflow and test conditions)
- TXV with subcooling specification→Check target subcooling(Verify airflow and test conditions)
- Before handoff→Verify controls, airflow and drainage(Record startup readings)
Installation Exam Topics
- Outdoor units
- 10%
- Packaged units
- 10%
- Copper tubing fabrication
- 10%
- Indoor equipment
- 13.33%
- Duct fabrication
- 6.67%
- Retrofitting
- 10%
- Duct installation
- 10%
- Startup and checkout
- 16.67%
- Evacuation and charging
- 13.33%
Equipment and Duct Setup
- ACCA Manual J
- Residential heating and cooling loads
- ACCA Manual S
- Selects equipment using performance data
- ACCA Manual D
- Residential duct design
- Split-system match
- Verify approved indoor-outdoor pairing
- Equipment clearances
- Follow manufacturer instructions and code
- Duct joints
- Seal with approved materials
- Flex duct
- Support and avoid sharp bends
- Condensate trap
- Install per equipment instructions
- Gas equipment checkout
- Verify combustion air and venting
- Startup record
- Log readings and control operation
- Packaged unit
- Main components share one cabinet
- Retrofit equipment selection
- Recheck capacity and duct compatibility
Refrigerant Circuit Setup
- Line set sizing
- Follow equipment piping tables
- Brazing purge
- Flow nitrogen to limit oxidation
- Pressure test
- Regulated dry nitrogen checks tightness
- Vacuum pump
- Removes moisture and noncondensables
- Micron gauge
- Measures deep vacuum
- Vacuum decay test
- Isolate pump and monitor rise
- Weigh-in
- Scale measures added refrigerant mass
- Charge adjustment
- Follow equipment line-length instructions
- Fixed-orifice charge check
- Superheat when specified
- Thermostatic expansion valve charge check
- Subcooling when specified for TXV
- Refrigerant identification
- Read equipment nameplate
Induced-Draft Ignition
Induce, prove draft, ignite, prove flame, circulate
Inducer startsIgniter prepares to light gasGas valve opens for trialCirculating blower follows delay
Draft Proving vs Flame Proving
Draft proving
- Pressure switch checks draft
- Follows inducer start
- Enables ignition sequence
Flame proving
- Flame sensor confirms ignition
- Follows gas valve opening
- Permits gas valve to remain open
Find the first missing sequence step
Cooling Diagnostic Picker
- No cooling call at equipment→Trace thermostat output and wiring
- Indoor coil iced→Thaw before testing airflow
- Weak airflow at several outlets→Check filter, blower and restrictions
- Normal airflow, poor cooling→Compare operating readings with specifications
- High superheat, low subcooling→Investigate undercharge and leakage(Compare against equipment targets)
- Possible liquid-line restriction→Check pressure drop across drier(If pressure taps are available)
- One room too warm→Measure branch airflow and inspect duct
Service Exam Topics
- Planned maintenance
- 13%
- Diagnostics
- 17%
- Flue analysis and leak detection
- 17%
- Retrofitting
- 10%
- System analysis
- 17%
- Cooling complaints
- 13%
- Heating complaints
- 13%
Heating Diagnostic Picker
- Inducer runs, draft unproved→Check vent, tubing and draft
- Burners light then drop out→Check flame signal and grounding
- Furnace opens high limit→Check temperature rise and airflow(Compare rise with rating plate)
- Flame rollout switch trips→Stop operation and investigate cause(Follow manufacturer service procedure)
- Outdoor coil stays iced→Check defrost sensors and control(Follow model’s defrost sequence)
- Heat pump stays in wrong mode→Check changeover command and valve
- Repair completed→Retest failed operating sequence(Log before and after readings)
Cooling and Heat Pump Service
- Low suction pressure
- Check airflow before interpreting charge
- Refrigerant leak
- Locate and repair before recharging
- Filter-drier restriction
- Look for excessive pressure drop
- TXV metering
- Regulates evaporator outlet superheat
- Reversing valve
- Switches refrigerant routing
- Heating-mode outdoor coil
- Absorbs outdoor heat
- Heat pump defrost
- Warms outdoor coil to melt frost
- Post-repair test
- Verify operation under original conditions
- Service record
- Log symptoms, readings and corrections
Furnace and Maintenance Checks
- Draft inducer
- Moves combustion gases
- Draft pressure switch
- Proves required pressure differential
- Flame sensor
- Confirms burner flame
- High limit
- Interrupts heat on overheating
- Rollout switch
- Detects overheating from flame rollout
- Furnace temperature rise
- Supply air temperature − return air
- Flue gas analyzer
- Measures gases such as CO
- Carbon monoxide
- Colorless, odorless combustion hazard
- Planned maintenance
- Inspect filters, coils and drains
Common Traps
Thermostat Off and Energy Isolation
Thermostat off stops the call ≠ Disconnect isolates electrical supply
Refrigerant Blend Saturation
Dew temperature for superheat ≠ Bubble temperature for subcooling
Control Demand and Load Power
Thermostat sends control demand ≠ Load circuit supplies operating power
Cooling Split and Heating Rise
Cooling split uses return minus supply ≠ Furnace rise uses supply minus return
Refrigerant Recovery and Evacuation
Recovery removes refrigerant ≠ Evacuation removes air and moisture
Frost and Defrost Faults
Light frost can occur normally ≠ Persistent ice calls for diagnosis
Certification and Refrigerant Work
NATE certifies HVAC proficiency ≠ Section 608 covers refrigerant handling
Last Minute
- 1.Pass all five CHP-5 exams
- 2.Verify isolation before resistance testing
- 3.Superheat uses vapor saturation temperature
- 4.Subcooling uses liquid saturation temperature
- 5.Duct airflow equals velocity times area
- 6.Check airflow before assessing refrigerant charge
- 7.Pressure-test before pulling a vacuum
- 8.Use manufacturer charging targets
- 9.Draft proving precedes furnace ignition
- 10.Compare furnace rise with rating plate
- 11.Retest and document operating readings
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