Mixed Deck — All CRD Topics Flashcards

In a closed-loop geothermal system, what is the primary purpose of the expansion tank?

Answer: Absorb fluid volume changes due to temperature fluctuation

The expansion tank accommodates the volumetric expansion and contraction of the loop fluid as its temperature changes, preventing dangerous pressure spikes.

Which window property most directly affects the cooling load from solar radiation?

Answer: Solar Heat Gain Coefficient (SHGC)

SHGC measures the fraction of incident solar radiation admitted through a window, making it the primary factor for solar-driven cooling loads.

Which document is typically completed and left with the homeowner after geothermal system commissioning?

Answer: A commissioning report including measured flow rates, temperatures, pressures, and COP calculations

A commissioning report documenting all measured parameters provides the homeowner and future technicians with a performance baseline for the system.

In residential load calculations, infiltration is typically measured using which unit?

Answer: ACH (air changes per hour)

Infiltration in residential buildings is expressed as ACH (air changes per hour), representing how many times the home's air volume is replaced by outdoor air.

A Thermal Response Test (TRT) is performed on a pilot borehole. What is the primary output used by the designer?

Answer: In-situ effective ground thermal conductivity and borehole thermal resistance

A TRT measures the temperature rise of circulating fluid under a constant heat injection rate to back-calculate the ground's effective thermal conductivity and borehole resistance.

Which of the following best describes 'degree-days' as used in energy consumption estimation?

Answer: Cumulative sum of daily mean temperature deviations from a base temperature (65°F)

Heating degree-days (HDD) sum the daily differences between 65°F and the average outdoor temperature, providing a seasonal measure of heating energy demand.

Which statement BEST describes the relationship between Certified Residential Geothermal Designer certification and industry evolution?

Answer: Requirements evolve periodically to reflect advances in knowledge and practice

Certification requirements evolve to keep pace with professional and technological advances.

How do environmental compliance regulations impact Residential Energy Efficiency & Load Calculations?

Answer: They ensure sustainable practices

Environmental compliance regulations impact Residential Energy Efficiency & Load Calculations by ensuring sustainable practices in geothermal system design and installation. These regulations mandate adherence to ecological guidelines, such as protecting groundwater quality and minimizing land disturbance, promoting environmentally responsible and long-term sustainable energy solutions.

What is a common tool used in Residential Energy Efficiency & Load Calculations?

Answer: Manual J and Manual S

Manual J and Manual S are common tools used in Residential Energy Efficiency & Load Calculations. ACCA Manual J is the industry standard for calculating a building's heating and cooling loads, while Manual S is used for properly selecting and sizing HVAC equipment based on those load calculations. Together, they ensure optimal system design and performance.

What minimum flow rate (gpm per ton) does IGSHPA typically recommend for closed-loop ground heat exchangers to maintain turbulent flow?

Answer: 1.5 gpm/ton

IGSHPA recommends approximately 1.5 gpm per ton to ensure turbulent flow regime and adequate heat transfer in ground loop piping.

Which design tool calculation method does ASHRAE recommend for sizing vertical bore fields in commercial and residential applications?

Answer: The g-function method using dimensionless borehole response functions

ASHRAE and IGSHPA recommend the g-function (Eskilson) method, which uses borehole response functions to account for thermal interference and long-term ground temperature changes.

Which stakeholder typically issues drilling permits for vertical borehole geothermal loops in US residential projects?

Answer: The state or local well drilling regulatory authority, often the department of natural resources or environmental quality

Vertical boreholes are regulated similarly to water wells, so state or local well drilling authorities issue required permits before drilling begins.

What is the purpose of a pre-construction site assessment in residential geothermal project management?

Answer: To identify site constraints such as setbacks, utility conflicts, soil conditions, and access for drilling equipment

A pre-construction site assessment identifies physical constraints that affect loop placement, equipment access, and overall project feasibility before signing contracts.

Why is proper ground loop configuration important in geothermal systems?

Answer: It improves heat exchange efficiency

Proper ground loop configuration is essential for maximizing the efficiency of heat transfer between the building and the earth. An optimized design ensures adequate contact with the ground and appropriate fluid flow, allowing the geothermal heat pump to extract or dissipate heat effectively. This directly impacts the system's energy performance, operational costs, and overall sustainability.

During a thermal response test (TRT), what two key ground parameters are determined?

Answer: Ground thermal conductivity and borehole thermal resistance

A TRT injects or extracts heat at a known rate and measures temperature response over time to calculate ground thermal conductivity and borehole thermal resistance.

What is the primary purpose of a geothermal heat pump system?

Answer: To transfer heat between the building and the ground

The primary purpose of a geothermal heat pump system is to efficiently transfer heat between a building and the stable temperature of the earth. In winter, it extracts heat from the ground to warm the building, and in summer, it moves heat from the building into the cooler ground. This process provides highly energy-efficient heating and cooling.

Which performance metric is used to evaluate a geothermal system's cooling efficiency during commissioning?

Answer: Energy Efficiency Ratio (EER) or Cooling COP

EER or Cooling COP compares cooling output to electrical input at specific test conditions, giving an instantaneous measure of cooling efficiency.

In a residential geothermal installation, why is it important to verify that the circuit breaker size matches the unit's Maximum Overcurrent Protection (MOP) rating on the nameplate?

Answer: Correct breaker sizing ensures adequate short circuit and overload protection without nuisance tripping

Installing a breaker at or below the nameplate MOP rating ensures proper overcurrent protection that safely interrupts faults while allowing normal starting current without nuisance trips.

In the IGSHPA design method, what does the 'run fraction' (PLF) account for?

Answer: Fraction of time the heat pump operates at full load during the design month

The part-load factor (PLF or run fraction) reflects that the heat pump cycles on and off, allowing the ground some thermal recovery between runs.

A designer is evaluating a pond loop for a residential system. What minimum pond volume (in acre-feet) per ton of system capacity is generally recommended?

Answer: 1.5 acre-ft per ton

Approximately 1.5 acre-feet of pond volume per ton of heating/cooling capacity is the commonly cited minimum to provide adequate thermal mass and recovery.