CRD System Commissioning & Performance Testing Flashcards

What does a Thermal Response Test (TRT) measure, and when is it typically conducted?

Answer: It measures in-situ ground thermal conductivity and borehole resistance, conducted before final loop design for large or complex installations

A TRT injects heat into a test borehole and monitors temperature recovery to accurately determine ground thermal properties used in final loop design.

How is the static pressure of a residential geothermal heat pump's air distribution system typically verified during commissioning?

Answer: By measuring total external static pressure with a manometer at the supply and return plenums

Total external static pressure measured at the unit's supply and return plenums confirms the air handler operates within its rated airflow range.

After commissioning a geothermal system, what ongoing monitoring is recommended to detect long-term ground loop degradation?

Answer: Annual recording of EWT, LWT, flow rate, and COP to track trends over time

Tracking EWT, LWT, flow rate, and COP annually allows early detection of loop degradation, flow issues, or equipment decline before failures occur.

Which defect would most likely be revealed by comparing measured versus design entering water temperatures during a first-year heating season performance review?

Answer: An undersized or improperly grouted ground loop causing higher-than-expected heat extraction

EWT that is lower than designed during heating suggests the loop is extracting more heat than it can sustainably supply, often due to inadequate sizing or poor thermal contact.

What is the purpose of verifying refrigerant superheat and subcooling during geothermal heat pump commissioning?

Answer: To confirm the refrigerant charge is correct and the heat exchanger is operating efficiently

Superheat and subcooling values confirm the refrigerant circuit has the correct charge and that heat exchangers are functioning properly within design parameters.

A residential geothermal installation fails the commissioning flow test because loop flow is 20% below design. What is the most likely cause?

Answer: Air remaining in the loop, an undersized circulating pump, or partially closed isolation valves

Low loop flow most commonly results from trapped air, a pump that is undersized for the loop length, or valves that were not fully opened during startup.