C-20 HVAC – Practice Exam 2

Welcome to your C-20 HVAC - Practice Exam 2

What is the correct clearance between a gas meter and electrical equipment?

What is the correct clearance between a gas meter and electrical equipment?Deselect Answer

No clearance is required between gas meters and electrical equipment

Gas meters must maintain a minimum 3-foot clearance from electrical meters, panels, and ignition sources per California Plumbing Code and utility requirements to prevent gas leaks from reaching ignition sources

A 6-inch clearance is sufficient between gas and electrical meters

Gas and electrical meters may be mounted side by side on the same wall with no clearance requirement

None

What does a split-system condenser fan that runs continuously even when the compressor is off indicate?

What does a split-system condenser fan that runs continuously even when the compressor is off indicate?Deselect Answer

The condenser fan running with compressor off is normal fan cycling behavior

The condenser fan contactor or control circuit is stuck closed — the fan motor is energized even when it should not be, indicating a failed contactor, shorted fan relay, or wiring error in the control circuit

The condenser fan runs continuously to pre-cool the coil before compressor startup

A continuously running condenser fan only indicates a wiring error during initial installation

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What personal protective equipment is required when handling dry nitrogen cylinders?

What personal protective equipment is required when handling dry nitrogen cylinders?Deselect Answer

No PPE is required for nitrogen — it is non-toxic and non-flammable

Safety glasses to protect against high-pressure gas release if a connection fails, and proper training on cylinder handling — nitrogen at high pressure can cause injury from rapid cylinder valve failure or connection blowout

A self-contained breathing apparatus is required when working with nitrogen cylinders

Nitrogen requires the same PPE as refrigerant cylinders — chemical-resistant gloves and face shield

None

When installing a split-system air conditioner in an attic, what special considerations apply?

When installing a split-system air conditioner in an attic, what special considerations apply?Deselect Answer

No special considerations are needed for attic installations

Attic installations require: adequate structural support for the air handler, proper access for service, drain pan and secondary drain provisions, high-temperature rated wiring and materials due to extreme attic temperatures, and provisions for servicing the equipment without hazard to the technician

Attic air handlers must always use horizontal discharge — vertical discharge is prohibited in attics

Air handlers may not be installed in attics per California code — only crawlspaces and closets are permitted

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What does the Solar Heat Gain Coefficient (SHGC) of a window represent?

What does the Solar Heat Gain Coefficient (SHGC) of a window represent?Deselect Answer

The R-value of the window's insulating glass unit

The fraction of solar radiation that passes through the window as heat gain — lower SHGC reduces cooling load from solar heat entering the building through windows

The UV transmittance of the window glazing

The percentage of visible light transmitted through the window

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What is the purpose of Manual H in heat pump system design?

What is the purpose of Manual H in heat pump system design?Deselect Answer

Manual H provides heat exchanger sizing calculations for commercial boilers

Manual H is the ACCA guide for designing heat pump systems — covering equipment selection, supplemental heat sizing, balance point analysis, and defrost cycle impacts on heating capacity

Manual H covers hydraulic calculations for hydronic heating systems

Manual H provides duct humidity control guidelines for humid climates

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What is the purpose of an energy model in commercial HVAC project planning?

What is the purpose of an energy model in commercial HVAC project planning?Deselect Answer

Energy models calculate structural loads on HVAC equipment supports

An energy model simulates building energy performance over a full year, predicting energy consumption for heating, cooling, lighting, and equipment — used for California Title 24 compliance, LEED certification, and evaluating system alternatives

Energy models are only used for residential projects in California

An energy model verifies that duct leakage meets Title 24 requirements

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What is the difference between supply air CFM and outdoor air CFM in a commercial HVAC system?

What is the difference between supply air CFM and outdoor air CFM in a commercial HVAC system?Deselect Answer

They are identical — all supply air comes from outdoors

Supply air CFM is the total volume of conditioned air delivered to the space — it includes recirculated return air mixed with the minimum required outdoor air CFM for ventilation. Outdoor air CFM is only the fraction of supply air drawn from outside the building

Outdoor air CFM is always greater than supply air CFM because outdoor air must be cooled before mixing with return air

The distinction only applies to exhaust-only ventilation systems, not standard HVAC

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What is the correct diagnostic approach when a gas furnace ignites and runs for approximately 30 seconds then shuts off, and attempts to restart two more times before locking out?

What is the correct diagnostic approach when a gas furnace ignites and runs for approximately 30 seconds then shuts off, and attempts to restart two more times before locking out?Deselect Answer

The thermostat is defective — replace it

Check the limit switch and temperature rise first — the furnace is likely overheating and tripping the limit switch due to restricted airflow (dirty filter, closed registers, failed blower) or incorrect blower speed setting

Replace the gas valve — 30-second runtime before shutdown indicates gas pressure failure

The igniter is failing — 30 seconds of operation then shutdown indicates the igniter is cooling and the flame is extinguishing

None

10.

When installing a heat pump in heating-dominated climate, what supplemental heat source is most commonly used?

When installing a heat pump in heating-dominated climate, what supplemental heat source is most commonly used?Deselect Answer

A gas furnace is always required as supplemental heat for heat pumps

Electric resistance heating strips installed in the air handler — energized by the heat pump thermostat when outdoor temperature drops below the balance point or during defrost cycles

A separate boiler system must be installed alongside all heat pump systems

Heat pumps do not require supplemental heat in any California climate zone

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11.

What is the purpose of measuring compressor amperage during system startup?

What is the purpose of measuring compressor amperage during system startup?Deselect Answer

Compressor amperage only needs to be measured annually during maintenance visits

Measuring startup (LRA) and running (RLA) amperage verifies the compressor is starting and running within nameplate specifications — excessive amperage indicates electrical or mechanical problems; low amperage may indicate the compressor is not pumping

Compressor amperage measurement is only required for three-phase commercial systems

Compressor amperage indicates the refrigerant charge level directly

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12.

What is the most likely cause when a furnace cycles the inducer on and off repeatedly without progressing to ignition?

What is the most likely cause when a furnace cycles the inducer on and off repeatedly without progressing to ignition?Deselect Answer

Normal pre-purge behavior — the furnace always cycles the inducer multiple times before ignition

A failed or partially blocked pressure switch sensing tube or condensate trap — the inducer runs but cannot satisfy the pressure switch, so the sequence pauses and retries

The gas valve has failed and must be replaced before ignition can occur

The igniter is not reaching temperature, preventing the control board from allowing gas valve energization

None

13.

What is the minimum clearance required between a gas furnace and the floor in a utility closet installation?

What is the minimum clearance required between a gas furnace and the floor in a utility closet installation?Deselect Answer

No floor clearance is required for gas furnaces

Clearance must meet the furnace manufacturer's installation instructions — for downflow furnaces, a combustion-resistant floor base is often required, and clearances from combustibles must meet listing requirements

A minimum 6-inch clearance from the floor is always required for all gas furnaces

Only upflow furnaces require floor clearance — downflow furnaces may be installed directly on any floor

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14.

What is the minimum insulation R-value required for supply ducts located in an unconditioned attic per California Title 24?

What is the minimum insulation R-value required for supply ducts located in an unconditioned attic per California Title 24?Deselect Answer

R-4.2

R-6.0

R-8.0

No insulation is required for supply ducts in attics

None

15.

What diagnostic test can be performed to determine if a compressor's internal valves are leaking?

What diagnostic test can be performed to determine if a compressor's internal valves are leaking?Deselect Answer

Measure suction pressure while the compressor is off to check for valve leakage

With the compressor running, close the suction service valve and observe how quickly suction pressure is pulled into a vacuum — a compressor with good valves should quickly pull deep vacuum; slow pull-down or inability to achieve vacuum indicates leaking valves or rings

Valve condition can only be determined by disassembling the compressor

Check compressor discharge temperature — high temperature indicates leaking valves

None

16.

When estimating the labor cost for a residential HVAC system replacement, what factor most significantly affects productivity?

When estimating the labor cost for a residential HVAC system replacement, what factor most significantly affects productivity?Deselect Answer

The weather conditions on installation day

The accessibility of the equipment location (attic, crawl space, closet), the complexity of the existing installation, and the distance from the truck to the equipment location — difficult access dramatically increases labor hours

The brand of equipment being installed

The day of the week the installation occurs

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17.

What is the minimum ventilation rate requirement per ASHRAE 62.2 for a typical 3-bedroom, 1,500-square-foot home?

What is the minimum ventilation rate requirement per ASHRAE 62.2 for a typical 3-bedroom, 1,500-square-foot home?Deselect Answer

No minimum ventilation is required if the home has operable windows

Total ventilation = 0.01 CFM per square foot of floor area plus 7.5 CFM per person (assuming 4 occupants) = 15 + 30 = 45 CFM total whole-building ventilation

A minimum of 25 CFM is required for all residential buildings regardless of size

Ventilation requirements are based on the number of bedrooms times 15 CFM each

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18.

What does it mean when the outdoor unit of a heat pump accumulates frost all over the outdoor coil during cold weather operation, and it never goes into defrost?

What does it mean when the outdoor unit of a heat pump accumulates frost all over the outdoor coil during cold weather operation, and it never goes into defrost?Deselect Answer

Heavy frost on the outdoor coil is normal during cold weather heat pump operation

The defrost control system has failed — a faulty defrost thermostat, defrost control board, or defrost relay is preventing the system from initiating the defrost cycle, allowing ice to accumulate until it blocks airflow completely and the system fails

Frost accumulation indicates refrigerant overcharge in heating mode

Heavy frost means the system is extracting maximum heat from the outdoor air — no corrective action needed

None

19.

What fall protection is required for HVAC technicians installing equipment through a roof opening?

What fall protection is required for HVAC technicians installing equipment through a roof opening?Deselect Answer

No fall protection is required for short-duration roof work

Any work at an unprotected roof opening requires fall protection — a personal fall arrest system, guardrails around the opening, or covers rated for the anticipated load must be in place before work begins per Cal/OSHA Title 8

Fall protection is only required when the roof opening exceeds 36 inches in diameter

The HVAC equipment being installed provides sufficient physical protection from falls through the opening

None

20.

What is the role of the California Mechanical Code in HVAC installation planning?

What is the role of the California Mechanical Code in HVAC installation planning?Deselect Answer

The California Mechanical Code only governs commercial HVAC installations

The California Mechanical Code (Title 24, Part 4) establishes minimum standards for HVAC equipment installation, duct construction, combustion air, venting, and clearances — all HVAC installations in California must comply with its requirements

The California Mechanical Code only applies to equipment over 5 tons capacity

The California Mechanical Code is identical to the national IMC with no California-specific amendments

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21.

What must be done when connecting a new gas appliance to an existing gas line that previously served a different appliance?

What must be done when connecting a new gas appliance to an existing gas line that previously served a different appliance?Deselect Answer

Simply connect the new appliance — existing gas lines are adequate for any appliance

Verify that the existing gas line is adequate in size for the new appliance's BTU/h demand, pressure test the line and new connections for leaks using an approved leak detection method, and verify that total connected load does not exceed the meter and regulator capacity

Contact the gas utility company to upgrade the service before any new appliance connection

Only visually inspect the connection for obvious leaks — pressure testing is not required for existing lines

None

22.

What does Cal/OSHA require regarding heat illness prevention for HVAC technicians working outdoors in summer?

What does Cal/OSHA require regarding heat illness prevention for HVAC technicians working outdoors in summer?Deselect Answer

Heat illness prevention only applies to agricultural workers — HVAC technicians are exempt

Cal/OSHA Title 8, Section 3395 requires employers to provide water (one quart per hour per worker), rest in shade, and an acclimatization period for new or returning workers — plus emergency response procedures when outdoor temperatures exceed 80 degrees F

Heat illness prevention measures only begin when outdoor temperature exceeds 100 degrees F

Only employers with more than 10 outdoor workers must comply with heat illness prevention requirements

None

23.

What is the OSHA permissible exposure limit (PEL) for carbon monoxide in the workplace?

What is the OSHA permissible exposure limit (PEL) for carbon monoxide in the workplace?Deselect Answer

25 ppm as an 8-hour TWA

35 ppm as a ceiling limit with no 8-hour TWA

50 ppm as an 8-hour time-weighted average (TWA)

100 ppm as an 8-hour TWA

None

24.

What is the correct procedure for verifying gas pressure at a newly installed furnace?

What is the correct procedure for verifying gas pressure at a newly installed furnace?Deselect Answer

Observe the flame color — a blue flame indicates correct gas pressure

Use a manometer connected to the manifold pressure tap to measure manifold pressure (typically 3.5 inches WC for natural gas, 10 inches WC for LP) and verify the supply pressure at the gas valve inlet is within the nameplate range

Gas pressure verification is the gas utility company's responsibility — HVAC contractors should not adjust gas pressure

Connect a pressure gauge to the gas meter outlet and compare to the nameplate rating

None

25.

What diagnostic reading confirms that a TXV (thermostatic expansion valve) is stuck open?

What diagnostic reading confirms that a TXV (thermostatic expansion valve) is stuck open?Deselect Answer

A stuck-open TXV causes high superheat at the evaporator outlet

A stuck-open TXV causes low or zero superheat — too much refrigerant floods the evaporator, liquid refrigerant reaches the compressor (slugging), suction pressure rises above normal, and the compressor may make liquid slugging sounds

A stuck-open TXV causes the system pressure to equalize between suction and discharge

A stuck-open TXV only affects heating operation in a heat pump system

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26.

When a capacitor tests low in microfarads compared to its rating, what symptoms may the motor exhibit?

When a capacitor tests low in microfarads compared to its rating, what symptoms may the motor exhibit?Deselect Answer

Low capacitor microfarad values have no effect on motor operation

A weak capacitor causes the motor to draw higher running amperage, run at reduced speed, overheat, and potentially fail to start under load — capacitors should be within 10% of rated microfarad value for reliable motor operation

A low capacitor value causes the motor to run faster than rated speed

Low capacitors only affect single-phase motors — three-phase motors do not use run capacitors

None

27.

What is the purpose of a manual shutoff valve on a refrigerant line set?

What is the purpose of a manual shutoff valve on a refrigerant line set?Deselect Answer

Manual shutoff valves regulate refrigerant flow during normal operation

Manual shutoff (service) valves allow isolation of system components for service — enabling refrigerant to be isolated in one part of the system without recovering the entire charge when servicing accessible components

Manual shutoff valves are safety devices that automatically close when high pressure is detected

Manual shutoff valves are required only on commercial systems above 5 tons

None

28.

What is the purpose of a building envelope tightness test (blower door test) in HVAC planning?

What is the purpose of a building envelope tightness test (blower door test) in HVAC planning?Deselect Answer

A blower door test measures duct leakage in the distribution system

A blower door test measures the overall air leakage rate of the building envelope — providing data for accurate infiltration load calculations and identifying areas for air sealing to improve efficiency

A blower door test verifies that all windows and doors close properly

A blower door test measures the static pressure developed by the air handling unit

None

29.

What type of pipe is required for condensate drainage from a high-efficiency (condensing) gas furnace?

What type of pipe is required for condensate drainage from a high-efficiency (condensing) gas furnace?Deselect Answer

Standard galvanized steel pipe

PVC or CPVC schedule 40 pipe — condensing furnace condensate is acidic (pH 3 to 5) and corrodes metal pipe

ABS plastic pipe is prohibited for condensate applications

Copper pipe is preferred for all condensate applications

None

30.

When troubleshooting an HVAC system, what does a very high temperature split (above 25 degrees F between return and supply) suggest?

When troubleshooting an HVAC system, what does a very high temperature split (above 25 degrees F between return and supply) suggest?Deselect Answer

A high temperature split indicates the system is operating with maximum efficiency

A high temperature split with restricted airflow suggests low airflow across the evaporator — the same volume of refrigerant is cooling a smaller mass of air. Check for dirty filter, blocked registers, failed blower motor, or low blower speed setting

High temperature split indicates refrigerant overcharge — too much refrigerant overcools the supply air

High temperature split above 25 degrees F is always normal in hot, humid weather

None

31.

What is the correct approach when a newly installed gas furnace produces a yellow or orange flame instead of the expected blue flame?

What is the correct approach when a newly installed gas furnace produces a yellow or orange flame instead of the expected blue flame?Deselect Answer

Yellow or orange flames are normal for natural gas furnaces during the first hour of operation

Yellow or orange flames indicate incomplete combustion — possible causes include insufficient combustion air, dirty burners, incorrect gas pressure, or a cracked heat exchanger disturbing combustion airflow. This condition produces elevated CO and must be corrected before occupant exposure

Adjust the gas valve to increase gas pressure — yellow flames indicate insufficient gas flow

Yellow flames are acceptable as long as the flame does not lift off the burner

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32.

What is the most likely cause when an air conditioning system cools well in the morning but loses capacity as the afternoon gets hotter?

What is the most likely cause when an air conditioning system cools well in the morning but loses capacity as the afternoon gets hotter?Deselect Answer

The system is correctly limiting capacity to prevent equipment damage in hot weather

Condenser coil is partially dirty or airflow is partially restricted — adequate at lower morning ambient temperatures but insufficient at peak afternoon temperatures when the condenser must reject maximum heat against a higher outdoor temperature

The thermostat is malfunctioning during afternoon hours only

The refrigerant charge is slightly low — the system loses capacity as the refrigerant boils off during the day

None

33.

What electrical hazard must HVAC technicians be aware of when working on equipment with two-speed or variable-speed motors?

What electrical hazard must HVAC technicians be aware of when working on equipment with two-speed or variable-speed motors?Deselect Answer

Variable-speed motors are no more hazardous than single-speed motors

Variable-speed drives (VFDs) and multi-speed motor controllers retain dangerous DC bus voltage for seconds to minutes after power is removed — the capacitors in the drive store lethal voltage that can discharge through a technician even after the disconnect is opened

Two-speed motors automatically de-energize when the disconnect is opened — no residual voltage hazard exists

Variable-speed motor hazards are limited to single-phase systems — three-phase VFDs de-energize instantly when disconnected

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34.

What is the Cal/OSHA requirement for ladders used to access rooftop HVAC equipment when the climb height exceeds 20 feet?

What is the Cal/OSHA requirement for ladders used to access rooftop HVAC equipment when the climb height exceeds 20 feet?Deselect Answer

Extension ladders may be used for any height with no special requirements

For climbs exceeding 20 feet, a ladder safety device (ladder cage, self-retracting lifeline, or ladder climbing system) may be required — consult Cal/OSHA requirements for the specific ladder type and application

Only fixed ship's ladders may be used for roof access exceeding 20 feet

Cal/OSHA has no specific requirements beyond using a ladder rated for the weight of the climber

None

35.

What is required when installing an HVAC system that requires a building permit in California?

What is required when installing an HVAC system that requires a building permit in California?Deselect Answer

Permits are not required for HVAC equipment replacements of the same capacity

A building permit must be obtained before work begins, the installation must comply with all applicable codes, and the work must be inspected and approved by the AHJ — operating equipment before final inspection is approved may require re-inspection or removal of work

Permits are only required for new construction HVAC systems, not replacements

The HVAC contractor's C-20 license serves as the permit — no separate building permit is required

None

36.

What type of sealant is required for sealing HVAC duct joints per California Title 24?

What type of sealant is required for sealing HVAC duct joints per California Title 24?Deselect Answer

Standard cloth duct tape is acceptable for all duct joint sealing

Listed duct sealant (mastic) or UL 181-listed pressure-sensitive tape — standard cloth duct tape is specifically prohibited for duct sealing per California Title 24 because it fails within a few years

Any commercially available tape rated for HVAC use is acceptable for duct sealing

Silicone caulk is the preferred sealant for all duct joints

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37.

What does the term 'infiltration' mean in HVAC load calculations?

What does the term 'infiltration' mean in HVAC load calculations?Deselect Answer

The flow of supply air into a room through supply registers

The uncontrolled leakage of outdoor air into a building through cracks, gaps, and openings in the building envelope — adding both sensible and latent load in summer and heat loss in winter

The controlled introduction of outdoor air through a ventilation system

The movement of air between floors through stairways and elevator shafts

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38.

What is the purpose of lockout/tagout procedures when servicing HVAC equipment?

What is the purpose of lockout/tagout procedures when servicing HVAC equipment?Deselect Answer

LOTO is only required for electrical hazards above 600 volts

LOTO ensures all energy sources (electrical, pneumatic, refrigerant pressure) are isolated and cannot be re-energized while a technician is performing maintenance — preventing unexpected startup or energy release that could cause injury

LOTO is only required in commercial settings — residential service does not require LOTO

Turning off the disconnect switch is equivalent to LOTO — no additional steps are required

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39.

What must an HVAC contractor do before beginning work on a system that may contain asbestos-insulated components?

What must an HVAC contractor do before beginning work on a system that may contain asbestos-insulated components?Deselect Answer

Begin work and be careful not to disturb any pipe insulation

Assume any pre-1980 HVAC system may contain asbestos — conduct an asbestos survey or assume ACM is present, stop work if ACM is disturbed, and comply with all Cal/OSHA and EPA asbestos regulations before proceeding

Only commercial systems built before 1980 contain asbestos — residential systems are always asbestos-free

Wet down any suspected asbestos materials and continue working

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40.

What is the purpose of a furnace's high-limit switch?

What is the purpose of a furnace's high-limit switch?Deselect Answer

The high-limit switch controls the blower on delay after a heating call

The high-limit switch is a safety device that shuts off the gas valve if the heat exchanger temperature exceeds a safe limit — preventing overheating that could crack the heat exchanger or cause a fire

The high-limit switch monitors outdoor temperature to adjust furnace output

The high-limit switch controls gas pressure at the manifold

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41.

When installing outdoor HVAC equipment, what must be considered regarding drainage?

When installing outdoor HVAC equipment, what must be considered regarding drainage?Deselect Answer

Drainage is not a concern for outdoor HVAC equipment

The equipment pad must be level to prevent oil migration in the compressor, and the area around the pad must drain away from the unit — standing water can cause corrosion, freeze damage, and impair condenser coil airflow

Outdoor units should be tilted slightly toward the building to prevent rain infiltration into the condenser

Only ground-source heat pumps require drainage planning — air-source equipment has no drainage concerns

None

42.

What is the purpose of a load calculation's internal heat gain component?

What is the purpose of a load calculation's internal heat gain component?Deselect Answer

Internal heat gain is added to the heating load to reduce furnace sizing

Internal heat gain accounts for heat generated by occupants, lighting, appliances, and equipment inside the building — this heat reduces the heating load but adds to the cooling load

Internal heat gain only applies to commercial buildings — residential calculations ignore internal gains

Internal gains only apply to the latent component of the cooling load

None

43.

What electrical component is used to start and run single-phase condenser fan motors?

What electrical component is used to start and run single-phase condenser fan motors?Deselect Answer

A transformer steps down voltage for fan motor operation

A run capacitor provides the phase shift needed for PSC motor starting and running — it is connected in series with the start winding and remains in the circuit during motor operation

A relay switches the fan motor between high and low speed

A variable frequency drive controls condenser fan speed on single-phase motors

None

44.

What is the purpose of Manual RS in residential HVAC design?

What is the purpose of Manual RS in residential HVAC design?Deselect Answer

Manual RS covers refrigerant safety for residential technicians

Manual RS (Comfort, Air Quality, and Efficiency by Design) is the ACCA guide providing a framework for designing complete residential HVAC systems — integrating load calculations, equipment selection, duct design, and indoor air quality into a coordinated whole-house design process

Manual RS is the residential supplement to ASHRAE 62.1 for ventilation design

Manual RS provides rating standards for residential HVAC equipment efficiency

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45.

What is the purpose of a job cost estimate's contingency allowance?

What is the purpose of a job cost estimate's contingency allowance?Deselect Answer

Contingency allowances cover profits on future change orders

A contingency allowance covers unforeseen costs that cannot be specifically identified at bid time — typically 5 to 15 percent of total estimated cost for HVAC projects, protecting the contractor from cost overruns on unknown conditions

Contingency is the same as overhead and profit

Contingency only applies to commercial projects over $500,000

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46.

What hazard is created by refrigerant contamination with air (non-condensables) in a refrigeration system?

What hazard is created by refrigerant contamination with air (non-condensables) in a refrigeration system?Deselect Answer

Air contamination improves system performance by increasing head pressure

Air in the system raises head pressure, reduces system efficiency and capacity, can accelerate refrigerant and oil breakdown, and makes proper charging impossible — but primarily, air with moisture can cause ice at the metering device and acid formation that destroys compressor components

Air contamination only affects the oil — refrigerant performance is not impacted by air

Air contamination is harmless in small amounts and self-purges through normal operation

None

47.

What is required when installing a split-system heat pump with the outdoor unit elevated on a wall bracket?

What is required when installing a split-system heat pump with the outdoor unit elevated on a wall bracket?Deselect Answer

Wall brackets are prohibited — all outdoor units must be installed on grade-level pads

The bracket must be rated for the combined weight of the unit plus a safety margin, properly anchored to the wall structure, and positioned to maintain required clearances and allow condensate to drain properly from the outdoor coil during defrost

Any wall bracket sold at a hardware store is acceptable for outdoor unit mounting

Wall-mounted outdoor units require a larger disconnect switch than ground-mounted units

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48.

What is the correct method for sizing a gas supply line to a new furnace?

What is the correct method for sizing a gas supply line to a new furnace?Deselect Answer

Use 3/4-inch black iron pipe for all residential furnace connections regardless of BTU/h demand

Use the gas pipe sizing tables in the California Plumbing Code or fuel gas code, accounting for the total BTU/h demand of all connected appliances, the available gas pressure, and the total length of pipe from the meter to the most remote appliance

Gas line sizing is the utility company's responsibility — the HVAC contractor only connects the appliance

Size the gas line based on the furnace's input BTU/h alone without considering other connected appliances

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49.

What does a yellow gas sticker or tag on a gas appliance mean when encountered during HVAC service?

What does a yellow gas sticker or tag on a gas appliance mean when encountered during HVAC service?Deselect Answer

A yellow tag means the appliance has been recently inspected and approved for operation

A yellow tag is placed by the gas utility on an appliance found to be unsafe — it indicates the gas supply has been shut off to that appliance and it must not be operated until repairs are made and the utility reinstates the gas supply

A yellow tag indicates the appliance requires a scheduled maintenance service

Yellow tags are used by contractors to identify appliances that need a refrigerant charge

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50.

What does it mean when an air conditioner suction line has frost extending from the evaporator coil all the way back to the outdoor unit?

What does it mean when an air conditioner suction line has frost extending from the evaporator coil all the way back to the outdoor unit?Deselect Answer

Frost on the suction line is normal during peak cooling days

Frost extending to the outdoor unit on the suction line indicates refrigerant is not fully vaporizing in the evaporator — liquid refrigerant is returning to the compressor, indicating very low superheat from either low charge, a stuck-open TXV, or severely restricted airflow

Suction line frost indicates the system needs defrost mode activated

Frost extending to the outdoor unit improves system efficiency by pre-cooling the refrigerant before compression

None

51.

What is the purpose of ASHRAE Standard 62.2 in residential HVAC design?

What is the purpose of ASHRAE Standard 62.2 in residential HVAC design?Deselect Answer

It sets minimum efficiency standards for residential HVAC equipment

It establishes ventilation rates for acceptable indoor air quality in residential buildings — specifying the amount of outdoor air that must be mechanically introduced to dilute indoor pollutants

It governs refrigerant management for residential systems

It sets maximum duct leakage rates for residential duct systems

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52.

What is the minimum safe concentration of refrigerant R-410A before evacuation of an occupied space is required per ASHRAE Standard 15?

What is the minimum safe concentration of refrigerant R-410A before evacuation of an occupied space is required per ASHRAE Standard 15?Deselect Answer

Any detectable amount requires evacuation

Evacuation is required when the refrigerant concentration reaches the Refrigerant Concentration Limit (RCL) — for R-410A, this is 0.44 kg/m3 (approximately 44,000 ppm). At or above this concentration, oxygen displacement creates an asphyxiation hazard

Evacuation is required at 10,000 ppm for all refrigerants

R-410A is safe at any concentration — evacuation is never required

None

53.

What is the purpose of safety relief valves on refrigerant systems?

What is the purpose of safety relief valves on refrigerant systems?Deselect Answer

Safety relief valves prevent refrigerant from being overcharged during service

Safety relief valves protect refrigerant vessels and systems from catastrophic failure by opening to release pressure when internal pressure exceeds a safe threshold — preventing container rupture that could cause explosion or missile projectile hazards

Safety relief valves are only required on refrigeration systems above 50 tons

Safety relief valves regulate operating pressure during normal system operation

None

54.

What does a building's U-factor represent in a heating and cooling load calculation?

What does a building's U-factor represent in a heating and cooling load calculation?Deselect Answer

The U-factor represents the thermal resistance of a building assembly

The U-factor is the overall heat transfer coefficient of a building assembly — the rate of heat flow in BTU per hour per square foot per degree F of temperature difference; lower U-factors indicate better insulating performance

The U-factor represents the solar heat gain coefficient of windows

The U-factor measures the air infiltration rate through the building envelope

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55.

What is the appropriate response when an HVAC technician encounters a confined space (such as a mechanical room) with an oxygen reading of 17 percent?

What is the appropriate response when an HVAC technician encounters a confined space (such as a mechanical room) with an oxygen reading of 17 percent?Deselect Answer

17 percent oxygen is acceptable — humans can work at reduced oxygen levels

Immediately evacuate the space and do not re-enter without respiratory protection (supplied air or SCBA) — 17 percent oxygen is below the Cal/OSHA minimum of 19.5 percent and constitutes an oxygen-deficient atmosphere that can cause rapid incapacitation and death

Put on a dust mask and continue working — the dust mask filters out the oxygen-displacing gas

Take several deep breaths of fresh air before entering, then work quickly to minimize exposure time

None

56.

What is the purpose of a duct leakage test per California Title 24?

What is the purpose of a duct leakage test per California Title 24?Deselect Answer

To verify the duct system meets minimum airflow requirements at each register

To measure air leakage from the duct system to outside the conditioned space — excessive leakage wastes conditioned air, reduces system efficiency, and must not exceed 15% of system airflow (or 6% for high-performance)

Duct leakage testing is only required for systems with more than 500 feet of ductwork

To verify that return air leakage does not exceed supply air leakage by more than 10%

None

57.

What is the purpose of a furnace's pressure switch in an induced-draft or condensing furnace?

What is the purpose of a furnace's pressure switch in an induced-draft or condensing furnace?Deselect Answer

The pressure switch measures gas supply pressure to the burner

The pressure switch proves that the inducer motor is operating and creating the negative pressure required for proper combustion and venting — the gas valve cannot energize unless the pressure switch confirms inducer operation

The pressure switch controls the blower speed based on system static pressure

The pressure switch is a redundant safety device that only activates during malfunction — it has no role in normal furnace operation

None

58.

What is the balance point of a heat pump system?

What is the balance point of a heat pump system?Deselect Answer

The outdoor temperature at which a heat pump switches from heating to cooling mode

The outdoor temperature at which the heat pump's heating output exactly equals the building's heating load — below this temperature, supplemental heat is needed to maintain comfort

The refrigerant charge level at which suction and discharge pressures are equal

The indoor temperature at which occupants are thermally comfortable without heating or cooling

None

59.

What is the proper first aid for skin contact with liquid refrigerant?

What is the proper first aid for skin contact with liquid refrigerant?Deselect Answer

Rub the affected area vigorously to restore circulation

Remove contaminated clothing, flush the affected skin with large amounts of lukewarm water for at least 15 minutes, and seek medical attention — liquid refrigerant causes frostbite-like freezing burns on skin contact

Apply heat to the affected area to warm the frostbitten tissue quickly

Liquid refrigerant contact only causes mild irritation — no first aid is required beyond rinsing

None

60.

What does a high wet-bulb temperature reading at the return air grille indicate?

What does a high wet-bulb temperature reading at the return air grille indicate?Deselect Answer

High wet-bulb at the return indicates the system is efficiently removing humidity

High wet-bulb temperature at the return air indicates high moisture content in the return air — the building has high indoor humidity, possibly from infiltration of humid outdoor air, occupant activities, or a failed dehumidification function of the cooling system

Wet-bulb temperature at the return is always higher than supply — this is normal

High return air wet-bulb indicates the evaporator coil is too cold and forming ice

None

61.

What is the purpose of a hard start kit on a single-phase compressor?

What is the purpose of a hard start kit on a single-phase compressor?Deselect Answer

A hard start kit increases the compressor's refrigerating capacity

A hard start kit (potential relay and start capacitor) provides additional starting torque to help the compressor start under high-pressure differential conditions — particularly useful in hot climates where the compressor restarts against high head pressure after short-cycling

A hard start kit is required by California code for all compressors above 3 tons

A hard start kit reduces compressor noise during startup

None

62.

What is the purpose of performing a temperature rise check on a gas furnace after startup?

What is the purpose of performing a temperature rise check on a gas furnace after startup?Deselect Answer

Temperature rise measures the efficiency of the heat exchanger coating

Temperature rise (the difference between supply air temperature and return air temperature) must be within the manufacturer's specified range — too low indicates excessive airflow (low efficiency), too high indicates insufficient airflow (potential heat exchanger damage)

Temperature rise verification is only required for commercial furnaces above 100,000 BTU/h

Temperature rise is checked to verify the thermostat is calibrated correctly

None

63.

What does elevated CO2 in the supply air stream indicate during furnace troubleshooting?

What does elevated CO2 in the supply air stream indicate during furnace troubleshooting?Deselect Answer

Elevated CO2 in supply air is normal — CO2 is a harmless byproduct of normal furnace operation

CO2 in the supply air stream indicates combustion gases are entering the air distribution system through a cracked or failed heat exchanger — a serious safety hazard requiring immediate furnace shutdown

CO2 in supply air indicates the outdoor air damper is bringing in outside air with elevated CO2

CO2 in supply air indicates the air filter needs replacement — debris absorbs CO2 from combustion

None

64.

What is the purpose of a Variable Air Volume (VAV) system compared to a Constant Air Volume (CAV) system?

What is the purpose of a Variable Air Volume (VAV) system compared to a Constant Air Volume (CAV) system?Deselect Answer

VAV systems use variable-speed compressors to modulate cooling capacity

VAV systems modulate airflow to each zone based on the zone's current load — reducing fan energy at part load and providing better zone-by-zone temperature control compared to CAV systems that deliver constant airflow regardless of load

VAV systems are less efficient than CAV systems but provide better humidity control

VAV systems are only used in residential applications — CAV is standard for commercial buildings

None

65.

What training does Cal/OSHA require for HVAC workers who may encounter hazardous materials on the job site?

What training does Cal/OSHA require for HVAC workers who may encounter hazardous materials on the job site?Deselect Answer

No specific training is required beyond on-the-job experience

Cal/OSHA Title 8, Section 5194 (Hazard Communication) requires training on: how to read and understand SDS, how to identify hazardous chemicals in the workplace, protective measures for each hazard, and emergency procedures — before workers are first exposed to hazardous chemicals

Hazardous material training is only required for chemical plant workers — HVAC is exempt

Only the HVAC contractor (not employees) needs hazardous material training

None

66.

What type of flue pipe is required for a Category IV condensing gas furnace?

What type of flue pipe is required for a Category IV condensing gas furnace?Deselect Answer

Standard Type B double-wall vent pipe

Listed PVC or CPVC special gas vent pipe, or AL29-4C stainless steel — Category IV appliances have positive flue pressure and acidic condensate that require corrosion-resistant, pressure-rated vent systems

Single-wall galvanized sheet metal B-vent

Any flue pipe rated for 400 degrees F is acceptable for condensing furnace venting

None

67.

What is the maximum length of flexible duct permitted between a duct collar and a supply register per California Mechanical Code?

What is the maximum length of flexible duct permitted between a duct collar and a supply register per California Mechanical Code?Deselect Answer

Flexible duct may be any length between the plenum and register

Maximum 14 feet per section of flexible duct, with a maximum of two 90-degree bends per section — manufacturer installation instructions may be more restrictive

Maximum 5 feet of flexible duct is permitted anywhere in a residential system

No length limit applies to flexible duct in residential systems

None

68.

What does it mean when a heat pump in heating mode produces warm air but the outdoor coil develops ice much faster than expected?

What does it mean when a heat pump in heating mode produces warm air but the outdoor coil develops ice much faster than expected?Deselect Answer

Rapid icing in heating mode is normal in cold, humid conditions

Rapid outdoor coil icing indicates insufficient heat absorption — caused by low refrigerant charge (reduced evaporator capacity), restricted outdoor airflow (dirty coil, failed fan), or very low outdoor temperature below the system's designed operating range

Fast icing indicates the defrost control is correctly detecting ice and will initiate defrost shortly

Rapid icing in heating mode indicates refrigerant overcharge — excess refrigerant floods the outdoor coil

None

69.

What is the purpose of a psychrometric process analysis for a cooling coil?

What is the purpose of a psychrometric process analysis for a cooling coil?Deselect Answer

To determine the refrigerant charge required for the coil

To determine the entering and leaving conditions (temperature, humidity, enthalpy) of the air passing through the coil — allowing calculation of sensible and latent capacity, and verifying the coil meets design requirements

To calculate the water flow rate required through a chilled water coil

To determine the required coil face velocity for acceptable noise levels

None

70.

What does a high superheat combined with low suction pressure indicate about a fixed orifice system?

What does a high superheat combined with low suction pressure indicate about a fixed orifice system?Deselect Answer

High superheat and low suction pressure indicate refrigerant overcharge

High superheat and low suction pressure indicate low refrigerant charge or a restriction upstream of the evaporator — the evaporator is fully active but insufficient refrigerant is boiling to maintain normal suction pressure

High superheat is always normal — it indicates the system is preventing liquid from reaching the compressor

High superheat with low suction pressure indicates a failed condenser fan motor

None

71.

What is the most appropriate response when a customer reports that their recently installed air conditioner is very noisy during operation?

What is the most appropriate response when a customer reports that their recently installed air conditioner is very noisy during operation?Deselect Answer

Advise the customer that all HVAC equipment produces noise and this is normal

Systematically identify the noise source: outdoor unit (compressor, condenser fan), indoor unit (blower, refrigerant flow), or ductwork (vibration, air velocity noise). Each has different causes and solutions. Excessive noise at startup may indicate a hard start issue; steady noise may indicate resonance between equipment and structure

Replace the compressor — noise always indicates compressor failure

Increase the blower speed to mask compressor noise with higher airflow velocity

None

72.

What is required when using an oxy-acetylene torch for brazing HVAC refrigerant tubing?

What is required when using an oxy-acetylene torch for brazing HVAC refrigerant tubing?Deselect Answer

Oxy-acetylene equipment may be used without restriction for HVAC brazing

Proper training and safety procedures are required: secure cylinders upright, use flashback arrestors on both torch hoses, keep cylinders away from heat and combustibles, purge torch of gas-air mixtures before lighting, never use oxygen to blow debris from surfaces, and never use oil or grease near oxygen equipment

Oxy-acetylene is prohibited for HVAC refrigerant line brazing — only propane torches are permitted

Only the acetylene tank needs safety precautions — oxygen is inert and requires no special handling

None

73.

What is the proper response when a technician suspects a gas leak while working on an HVAC system?

What is the proper response when a technician suspects a gas leak while working on an HVAC system?Deselect Answer

Use a lit lighter or match to locate the source of the gas smell

Immediately shut off the gas supply if safely possible, evacuate all occupants from the building, call the gas utility from a location away from the building, and do not re-enter until the utility confirms the leak is repaired and the building is safe

Open windows for ventilation, continue working, and look for the leak source while the space ventilates

Gas leaks small enough to smell are not dangerous — only large leaks require evacuation

None

74.

What is the correct diagnostic approach when a customer reports the system is cooling but not reaching the thermostat setpoint on the hottest days?

What is the correct diagnostic approach when a customer reports the system is cooling but not reaching the thermostat setpoint on the hottest days?Deselect Answer

Replace the thermostat — it is incorrectly sensing temperature

Measure outdoor temperature, indoor return air temperature, suction and discharge pressures, superheat and subcooling, and supply-return air temperature split — compare all readings to design conditions to determine if the issue is equipment performance, load, or both

Add refrigerant to increase capacity for peak summer days

Increase fan speed to deliver more airflow and improve cooling capacity

None

75.

What information does a duct system pressure drop calculation provide?

What information does a duct system pressure drop calculation provide?Deselect Answer

The total weight of ductwork in the system

The resistance to airflow at design flow rates through each duct section — used to size ducts so the system delivers design airflow to each room without exceeding the air handling unit's available static pressure

The maximum temperature of supply air at the furthest register

The total BTU capacity lost to duct conduction in an unconditioned attic

None

76.

What respiratory protection is required when working in an area with confirmed mold growth in HVAC ductwork?

What respiratory protection is required when working in an area with confirmed mold growth in HVAC ductwork?Deselect Answer

No respiratory protection is needed — mold in ducts is a minor issue

At minimum an N95 particulate respirator, and a half-face respirator with P100 filters for more extensive mold exposure — full protective clothing and gloves are also recommended to prevent skin contact and cross-contamination

A standard surgical mask provides sufficient mold protection for HVAC technicians

Only an environmental hygienist may work in areas with HVAC duct mold — technicians must wait for clearance

None

77.

What is the purpose of a heat pump's auxiliary heat lockout control?

What is the purpose of a heat pump's auxiliary heat lockout control?Deselect Answer

The auxiliary heat lockout prevents electric strips from operating in cooling mode

The auxiliary heat lockout (often an outdoor thermostat) prevents electric resistance strips from energizing when outdoor temperature is above a set point — ensuring the more efficient heat pump handles the load when it can, reducing operating costs

The auxiliary heat lockout is a safety device that prevents simultaneous compressor and strip heater operation

The auxiliary heat lockout ensures backup heat does not operate during peak demand utility rate periods

None

78.

What is the purpose of Manual CS in commercial HVAC applications?

What is the purpose of Manual CS in commercial HVAC applications?Deselect Answer

Manual CS covers commissioning and startup procedures for commercial systems

Manual CS (Commercial Application, Systems, and Equipment) is the ACCA guide covering system selection and application for commercial HVAC — including central station air handling, variable air volume systems, rooftop units, and chiller plants

Manual CS covers California-specific code supplements to commercial HVAC design

Manual CS is a condensate system design guide for commercial buildings

None

79.

What is the purpose of a zone damper in a multi-zone HVAC system?

What is the purpose of a zone damper in a multi-zone HVAC system?Deselect Answer

Zone dampers control refrigerant flow to each zone's evaporator coil

Zone dampers are motorized dampers installed in duct branches that open and close to direct conditioned airflow to occupied zones based on individual zone thermostat demands — allowing one central system to serve multiple independently controlled areas

Zone dampers bypass excess airflow back to the return plenum to prevent pressure buildup

Zone dampers are manual valves adjusted seasonally to balance winter and summer airflow distribution

None

80.

What is the purpose of a heat load calculation's duct loss component?

What is the purpose of a heat load calculation's duct loss component?Deselect Answer

Duct losses are only calculated for systems with flexible duct

Duct losses account for heat transferred through duct walls when ducts run through unconditioned spaces (attics, crawlspaces) — reducing delivered heating or cooling capacity and increasing energy consumption

Duct losses only apply to cooling calculations — heating systems are not affected by duct location

Duct loss calculations are optional under California code for residential systems

None

81.

What is the purpose of combustion air openings when installing a gas furnace in an enclosed utility room?

What is the purpose of combustion air openings when installing a gas furnace in an enclosed utility room?Deselect Answer

Combustion air openings allow excess heat from the furnace to escape to prevent overheating

Gas appliances require combustion air openings to provide adequate outdoor air for combustion and draft — without sufficient combustion air, the furnace produces incomplete combustion, CO, and may backdraft combustion gases into the living space

Combustion air openings are only required for furnaces above 100,000 BTU/h input

Modern sealed-combustion furnaces never require combustion air openings regardless of installation location

None

82.

What does a wet or damp return air duct indicate in a forced-air cooling system?

What does a wet or damp return air duct indicate in a forced-air cooling system?Deselect Answer

Moisture in return ducts is normal condensation that drains naturally

Moisture in return ducts indicates negative pressure is drawing humid air (from unconditioned crawl spaces or attics) into the return system through duct leaks or unsealed penetrations — causing high indoor humidity, mold growth potential, and energy waste

Wet return ducts indicate the evaporator coil is frosted and thawing water is entering the duct

Wet return ducts only occur in high-humidity climates and are not a concern in California

None

83.

What is Manual Q used for in HVAC system design?

What is Manual Q used for in HVAC system design?Deselect Answer

Manual Q provides quality control checklists for HVAC installation inspections

Manual Q covers low-pressure, low-velocity duct system design — providing methods for designing duct systems that operate at pressures below 0.25 inches WC for maximum energy efficiency and acoustic performance

Manual Q covers refrigerant quantity calculations for various equipment capacities

Manual Q provides quick-reference tables for equipment selection without load calculations

None

84.

What is the purpose of return air plenums in a residential forced-air system?

What is the purpose of return air plenums in a residential forced-air system?Deselect Answer

Return air plenums collect exhaust air from the building for disposal

Return air plenums collect air from the conditioned space and return it to the air handling unit for reconditioning — providing the return air path that balances supply air delivery to maintain neutral building pressure

Return air plenums are only required for systems over 3 tons capacity

Return air plenums must be sealed from the living space to prevent noise transmission

None

85.

What is the most likely cause when an air conditioner's discharge line (hot gas line) is cool to the touch?

What is the most likely cause when an air conditioner's discharge line (hot gas line) is cool to the touch?Deselect Answer

A cool discharge line is normal in mild weather

A cool discharge line indicates the compressor is not pumping — the refrigerant is not being compressed and heated. Possible causes include a failed compressor, open start or run capacitor, or open compressor motor winding

A cool discharge line indicates the system is efficiently rejecting heat to the outdoors

A cool discharge line indicates refrigerant overcharge — excess liquid is cooling the discharge gas

None

86.

What is the proper method for connecting a PVC condensate drain to a building's plumbing drainage system?

What is the proper method for connecting a PVC condensate drain to a building's plumbing drainage system?Deselect Answer

Connect directly to any convenient drain line without an air gap

Connect through an indirect waste receptor (air gap) — the condensate drain must not connect directly to the sanitary drain system to prevent sewer gas from entering the HVAC equipment

Connect directly to the sewer line using a wye fitting for the most reliable drainage

Condensate may be discharged to a floor drain without any connection to the building drain system

None

87.

What is the correct way to safely discharge pressure from a refrigerant system before opening for service?

What is the correct way to safely discharge pressure from a refrigerant system before opening for service?Deselect Answer

Open a service valve slowly and allow refrigerant to vent to the atmosphere until pressure equals atmospheric

Connect a certified recovery machine to recover all refrigerant from the system into an approved recovery cylinder before opening any connections — EPA Section 608 prohibits venting any refrigerant

Close the service valves and allow the refrigerant to slowly leak out through the Schrader valve cores overnight

Discharge refrigerant through a bucket of water to absorb the refrigerant before it reaches the atmosphere

None

88.

What is the purpose of a commissioning report's airflow measurements?

What is the purpose of a commissioning report's airflow measurements?Deselect Answer

Airflow measurements verify the filter is properly installed

Airflow measurements document the actual delivered airflow at each supply register and total system airflow — verifying the duct system delivers design airflow to each room for comfort and system efficiency

Airflow measurements are only required for commercial systems per California code

Airflow measurements verify the blower motor is operating at nameplate amperage

None

89.

What is required when installing HVAC equipment on a rooftop where the roof has a parapet wall?

What is required when installing HVAC equipment on a rooftop where the roof has a parapet wall?Deselect Answer

No special considerations are needed for parapet wall installations

Clearance requirements for the outdoor unit must be measured from the parapet height if it restricts airflow — parapet walls can act as wind barriers that recirculate hot discharge air back into the condenser intake, significantly reducing system performance

Parapet walls always improve condenser performance by blocking wind that would otherwise disturb airflow

Parapet wall height determines the required disconnect switch height for rooftop equipment

None

90.

What is the purpose of an air balance in a multi-zone HVAC system after installation?

What is the purpose of an air balance in a multi-zone HVAC system after installation?Deselect Answer

Air balancing adjusts refrigerant charge to each zone

Air balancing measures and adjusts the airflow to each zone by setting damper positions, balancing dampers, or adjusting fan speeds — ensuring each zone receives its design airflow for comfort and proper system operation

Air balancing is only performed on commercial systems with variable air volume controls

Air balancing is only required when occupants complain about temperature differences between rooms

None

91.

What are the key provisions of ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) relevant to HVAC contractors?

What are the key provisions of ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) relevant to HVAC contractors?Deselect Answer

ASHRAE 15 only applies to industrial refrigeration systems above 50 tons

ASHRAE 15 establishes safety requirements for refrigeration equipment rooms including ventilation, leak detection, emergency controls, and refrigerant concentration limits — these requirements affect commercial HVAC equipment room design and maintenance

ASHRAE 15 only governs refrigerant selection and does not address installation safety

ASHRAE 15 is a voluntary guideline with no enforcement mechanism in California

None

92.

What is the correct method for verifying that a newly installed gas furnace is not producing dangerous levels of carbon monoxide?

What is the correct method for verifying that a newly installed gas furnace is not producing dangerous levels of carbon monoxide?Deselect Answer

Observe the burner flame color — a blue flame indicates no CO production

Use a calibrated combustion analyzer in the supply air stream downstream of the heat exchanger to measure CO in parts per million while the furnace operates at steady state — CO below 9 ppm in the air stream indicates safe operation

Carbon monoxide testing is only required for commercial furnaces

CO monitoring is only required during annual maintenance — not at initial startup

None

93.

What is the correct PPE for an HVAC technician performing hot work (brazing) in a confined space such as a utility closet?

What is the correct PPE for an HVAC technician performing hot work (brazing) in a confined space such as a utility closet?Deselect Answer

Safety glasses and work gloves are sufficient for brazing in any location

In confined spaces: safety glasses or face shield, heat-resistant gloves, fire-resistant clothing, ventilation to remove combustion products and torch gases, a fire extinguisher immediately accessible, and monitoring for oxygen depletion — propane and acetylene torches consume oxygen in enclosed spaces

A dust mask provides adequate respiratory protection during brazing in confined spaces

No additional PPE beyond standard brazing PPE is needed in confined spaces — ventilation is optional

None

94.

What does a humming noise from a compressor that fails to start indicate?

What does a humming noise from a compressor that fails to start indicate?Deselect Answer

The compressor is starting normally — humming during startup is expected

The compressor motor is attempting to start but cannot — possible causes include a failed start capacitor, seized compressor, incorrect voltage, or a stuck scroll. The motor hums because it is receiving power but cannot develop starting torque

Humming indicates the compressor's vibration isolators are worn and need replacement

A humming compressor indicates refrigerant overcharge preventing startup

None

95.

A residential HVAC system serves a 2,000-square-foot home with a calculated total cooling load of 36,000 BTU/h. What size system in tons should be selected?

A residential HVAC system serves a 2,000-square-foot home with a calculated total cooling load of 36,000 BTU/h. What size system in tons should be selected?Deselect Answer

2 tons

2.5 tons

3 tons

4 tons

None

96.

What is the purpose of commissioning an HVAC system's controls and thermostat after installation?

What is the purpose of commissioning an HVAC system's controls and thermostat after installation?Deselect Answer

Controls commissioning is only required for commercial systems with BAS

Controls commissioning verifies that all temperature sensors, damper actuators, and safety controls operate correctly — confirming the system starts, stages, and shuts down as designed under various operating conditions

Controls commissioning is limited to setting the clock and program on the thermostat

Controls are factory-tested and require no field verification after installation

None

97.

What maintenance is recommended annually for a residential split-system air conditioner?

What maintenance is recommended annually for a residential split-system air conditioner?Deselect Answer

Only replacing the air filter is needed annually for AC systems

Clean condenser coil, check and clean evaporator coil if accessible, verify refrigerant pressures and temperatures, check electrical connections and measure operating amperage, lubricate motor bearings if required, verify condensate drain operation, check thermostat calibration, and replace air filter

Annual maintenance is not needed for systems under 5 years old

Clean condenser coil and replace capacitor annually regardless of condition

None

98.

What is a cooling tower and what role does it play in large commercial HVAC systems?

What is a cooling tower and what role does it play in large commercial HVAC systems?Deselect Answer

A cooling tower is a large evaporative cooler used for direct space cooling in industrial buildings

A cooling tower rejects heat from chilled water systems to the atmosphere through evaporative cooling of condenser water — allowing water-cooled chillers to operate more efficiently than air-cooled equipment

A cooling tower is a storage tank that stores chilled water for peak demand reduction

A cooling tower is an air-side economizer that cools outdoor air before it enters the building

None

99.

What is the correct clearance above the supply air outlet of a furnace before it enters the duct system (plenum clearance)?

What is the correct clearance above the supply air outlet of a furnace before it enters the duct system (plenum clearance)?Deselect Answer

No clearance is required between the furnace outlet and the duct connection

Manufacturer installation instructions specify the minimum plenum height and clearance from combustibles — typically 1 inch from the top of the furnace to sheet metal plenums and greater clearances from combustible materials

A minimum 6-inch clearance is required above all furnace outlets regardless of manufacturer requirements

Plenum clearances are only required for heat pumps, not gas furnaces

None

100.

What electrical safety practice is essential when replacing a capacitor on an HVAC condenser unit?

What electrical safety practice is essential when replacing a capacitor on an HVAC condenser unit?Deselect Answer

Capacitors discharge automatically when the unit is turned off — no additional steps are needed

Before handling a capacitor, discharge it by connecting a resistor or insulated screwdriver across its terminals — capacitors can retain lethal voltage for hours after power is removed even when the system is not running

Capacitors are safe to handle as long as the main disconnect switch is open

Discharge the capacitor by shorting the terminals directly with a screwdriver or pliers — the spark is harmless

None

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