CSLB General Building (B) — All Questions
← Back to practice22 questions
In residential load calculations, what does an ACCA Manual J procedure primarily determine?
- a.The size and gauge of supply ductwork
- b.The heating and cooling loads of a building based on its construction and climate✓
- c.The refrigerant charge required for the condenser
- d.The electrical service size for the panel
Manual J is the industry-standard residential load calculation method. It estimates the sensible and latent heating and cooling loads by accounting for construction, insulation, windows, orientation, infiltration, and local design temperatures. Equipment is then selected to match those calculated loads.California Energy Code (Title 24)
One ton of cooling capacity is equal to how many BTU per hour?
- a.6,000 BTU/hr
- b.9,000 BTU/hr
- c.12,000 BTU/hr✓
- d.15,000 BTU/hr
A ton of refrigeration equals 12,000 BTU/hr, derived from the heat needed to melt one ton of ice in 24 hours. This unit is the standard used to size air-conditioning and heat-pump equipment. A 3-ton system therefore provides about 36,000 BTU/hr of cooling.
A common rule-of-thumb airflow value for a residential cooling system is approximately how many CFM per ton?
- a.100 CFM per ton
- b.400 CFM per ton✓
- c.800 CFM per ton
- d.1,200 CFM per ton
Standard residential cooling airflow is roughly 400 CFM per ton, though it may range from 350 to 450 depending on climate and humidity. A 3-ton system therefore typically moves about 1,200 CFM. Correct airflow is essential for proper capacity and dehumidification.
A 4-ton air-conditioning system is designed at 400 CFM per ton. What total supply airflow is required?
- a.800 CFM
- b.1,200 CFM
- c.1,600 CFM✓
- d.2,000 CFM
Multiply tons by CFM per ton: 4 tons x 400 CFM = 1,600 CFM. Sizing the blower and ductwork for this airflow ensures the coil receives adequate air for rated capacity. Undersized ducts would restrict this airflow and reduce performance.
The sensible heat formula uses which constant when air volume is in CFM and temperature difference is in degrees F?
- a.0.68
- b.1.08✓
- c.4.5
- d.0.24
Sensible heat (BTU/hr) equals 1.08 x CFM x delta-T, where 1.08 combines air density, specific heat, and a time conversion. The 4.5 factor is used with enthalpy for total heat, and 0.68 is used for latent load with grains of moisture. These formulas let technicians verify airflow and capacity.
Using the sensible heat formula, how much sensible heat is removed when 1,200 CFM of air is cooled through a 20 degree F temperature drop?
- a.12,960 BTU/hr
- b.18,000 BTU/hr
- c.25,920 BTU/hr✓
- d.32,400 BTU/hr
Sensible heat = 1.08 x 1,200 CFM x 20 F = 25,920 BTU/hr. This calculation lets a technician confirm the coil is delivering close to its rated capacity. A result far below expected suggests low airflow or an undercharged system.
What does ACCA Manual D provide guidance for?
- a.Selecting the correct condenser
- b.Sizing and designing residential duct systems✓
- c.Calculating building heat loss
- d.Selecting the proper thermostat
Manual D is the ACCA standard for residential duct design. It uses the available static pressure and required airflow to size trunks, branches, and fittings so each room receives its design CFM. Proper duct design prevents noise, high static pressure, and uneven comfort.
After a Manual J load is calculated, which ACCA procedure is used to select the specific equipment model?
- a.Manual D
- b.Manual T
- c.Manual S✓
- d.Manual RS
Manual S matches equipment to the Manual J loads using manufacturer expanded performance data at local design conditions. It ensures the unit meets both sensible and latent loads without gross oversizing. Oversized equipment short-cycles and dehumidifies poorly.
Oversizing a residential air conditioner most commonly leads to which problem?
- a.Higher heating capacity
- b.Short cycling and poor humidity control✓
- c.Lower refrigerant pressures
- d.Reduced supply air temperature
An oversized unit cools the air quickly and satisfies the thermostat before it runs long enough to remove moisture, causing short cycling. The result is a cool but clammy space and increased wear from frequent starts. Correct sizing from Manual J and S avoids this.
Which factor increases a building's cooling load the most on a hot afternoon?
- a.Large west-facing glass with direct solar gain✓
- b.North-facing insulated walls
- c.A well-sealed attic hatch
- d.Low-wattage LED lighting
West-facing windows receive intense direct solar radiation in the afternoon, adding substantial sensible heat gain. This solar load is often a dominant component of the peak cooling load. Shading and low-SHGC glazing reduce this gain.
In California, plans for new HVAC systems typically must demonstrate compliance with which energy standard?
- a.The National Electrical Code
- b.Title 24, Part 6 energy efficiency standards✓
- c.The Uniform Plumbing Code
- d.The Americans with Disabilities Act
Title 24, Part 6 sets California's building energy efficiency standards, including HVAC equipment efficiency, duct sealing, and refrigerant charge verification. New and altered systems generally must show compliance through prescriptive or performance methods. Documentation is submitted with the permit application.California Energy Code (Title 24)
Under the California Mechanical Code, when is a permit generally required for HVAC work?
- a.Only for commercial buildings
- b.Only when replacing a thermostat
- c.When installing, altering, or replacing mechanical equipment such as a furnace or air conditioner✓
- d.Never for residential work
The CMC and local jurisdictions require a mechanical permit for installing, altering, or replacing regulated equipment like furnaces, air conditioners, and ductwork. Permits trigger inspection to verify code-compliant, safe installation. Minor maintenance such as filter changes does not require a permit.2022 California Mechanical Code (CMC)
What is the primary purpose of a Manual J block load versus a room-by-room load?
- a.To size the refrigerant lines
- b.To establish total equipment capacity for the whole structure✓
- c.To determine duct insulation R-value
- d.To calculate the gas meter size
A block (whole-house) load establishes the total heating and cooling capacity the equipment must provide. A room-by-room load then distributes that capacity to size individual ducts and registers. Both are needed for a complete design.
If a home has a calculated cooling load of 30,000 BTU/hr, what nominal equipment size is the closest match?
- a.2 tons
- b.2.5 tons✓
- c.3.5 tons
- d.4 tons
30,000 BTU/hr divided by 12,000 BTU/hr per ton equals 2.5 tons. Manual S guides selecting a unit whose capacity at design conditions closely matches this load. Choosing 2.5 tons avoids the humidity and cycling problems of oversizing.
Friction rate in duct design is typically expressed in which units?
- a.CFM per square foot
- b.BTU per hour
- c.Inches of water column per 100 feet of duct✓
- d.Feet per minute
Friction rate expresses the pressure loss per unit length of duct, in inches of water column per 100 feet. In Manual D, the available static pressure and total effective length set the design friction rate used to size ducts. A higher friction rate yields smaller, higher-velocity ducts.
Air velocity in a duct is calculated by dividing airflow (CFM) by what?
- a.The duct length
- b.The cross-sectional area of the duct in square feet✓
- c.The static pressure
- d.The temperature difference
Velocity in feet per minute equals CFM divided by the duct cross-sectional area in square feet. Excessive velocity causes noise and high friction losses, while too little velocity can reduce throw and mixing. Designers balance velocity against static pressure limits.
A branch duct must deliver 200 CFM at a velocity of about 600 feet per minute. Approximately what free area is required?
- a.0.10 square feet
- b.0.20 square feet
- c.0.33 square feet✓
- d.0.66 square feet
Area equals CFM divided by velocity: 200 / 600 = 0.33 square feet. This corresponds to roughly a 8-inch round duct. Selecting the right size keeps velocity and noise within acceptable limits.
Under California energy standards, duct leakage in many new and altered systems must be verified by which method?
- a.Visual inspection only
- b.A duct leakage (pressurization) test by a certified rater or installer✓
- c.A refrigerant pressure test
- d.A combustion analysis
Title 24 requires duct leakage testing for many new installations and changeouts, typically verified through a pressurization test. Sealing ducts reduces energy waste and improves delivered airflow. Results are often confirmed by a HERS rater.California Energy Code (Title 24)
Which condition would a technician correct by performing an accurate load calculation instead of using a rule of thumb like square footage per ton?
- a.Chronic comfort complaints from an oversized or undersized system✓
- b.A dirty condenser coil
- c.A tripped float switch
- d.A failed run capacitor
Square-foot rules of thumb ignore insulation, glazing, orientation, and infiltration, often producing oversized or undersized equipment and comfort complaints. A Manual J load accounts for these variables and yields correctly sized equipment. This is the proper professional approach.
Latent load in a cooling calculation refers to the energy required to do what?
- a.Raise the dry-bulb temperature of the air
- b.Remove moisture (water vapor) from the air✓
- c.Overcome duct friction
- d.Power the compressor motor
Latent load is the heat associated with condensing water vapor out of the air, lowering humidity. Sensible load changes air temperature, while latent load changes moisture content. Both must be met for comfort, especially in humid climates.
A 3-ton system is selected for a home. At 400 CFM per ton, what is the target blower airflow?
- a.800 CFM
- b.1,000 CFM
- c.1,200 CFM✓
- d.1,500 CFM
3 tons x 400 CFM per ton = 1,200 CFM. The blower and duct system should be configured to deliver this airflow at the system's external static pressure. Verifying actual airflow after installation confirms proper capacity.
What is the main benefit of properly sizing equipment to a load calculation rather than oversizing?
- a.Faster refrigerant charging
- b.Better humidity control, comfort, and energy efficiency✓
- c.Elimination of the need for a permit
- d.Higher supply air velocity
Right-sized equipment runs longer, steadier cycles that dehumidify effectively and hold temperature evenly, improving comfort and efficiency. Oversizing wastes energy through short cycling and leaves the space humid. This aligns with Title 24 efficiency goals.California Energy Code (Title 24)