CRD Ground Loop & Heat Pump Configuration 2 — Questions and Answers
Question 1: What is the primary reason a designer would choose a slinky horizontal ground loop over a straight horizontal loop?
- Lower pumping energy due to reduced pipe length
- More heat exchange surface area per linear trench foot (Correct answer)
- Better freeze protection in cold climates
- Easier pressure testing after installation
Correct answer: More heat exchange surface area per linear trench foot
Slinky coils pack more pipe into each trench foot, increasing heat exchange area when land area is limited.
Question 2: In a series ground loop circuit, how does flow rate compare to a parallel circuit of the same total pipe length?
- Series requires higher flow rate to maintain equivalent Reynolds number
- Series uses lower flow rate because all fluid travels the same path (Correct answer)
- Series and parallel require identical flow rates
- Series flow rate depends only on the heat pump tonnage
Correct answer: Series uses lower flow rate because all fluid travels the same path
In a series circuit, one flow stream passes through all pipes sequentially, so the required flow rate is lower than a parallel circuit handling the same total heat transfer.
Question 3: A standing column well (SCW) differs from a closed-loop vertical bore primarily because:
- SCW uses antifreeze solution to prevent freezing
- SCW draws groundwater up and returns it to the same well (Correct answer)
- SCW requires no pump since water rises by artesian pressure
- SCW pipes are made of HDPE rather than steel
Correct answer: SCW draws groundwater up and returns it to the same well
A standing column well circulates open-loop groundwater within a single deep well, bleed-and-return, rather than a sealed fluid loop.
Question 4: Which parameter most directly determines whether a heat pump operates in heating or cooling mode?
- Outdoor air temperature
- Reversing valve position (Correct answer)
- Compressor speed
- Entering water temperature
Correct answer: Reversing valve position
The reversing valve switches refrigerant flow direction, determining which coil acts as condenser or evaporator and thus the operating mode.
Question 5: For a vertical closed-loop system in saturated soil, what is the typical design range for heat extraction per bore foot?
- 5–10 BTU/hr·ft
- 20–50 BTU/hr·ft (Correct answer)
- 75–100 BTU/hr·ft
- 120–150 BTU/hr·ft
Correct answer: 20–50 BTU/hr·ft
Saturated soils typically yield 20–50 BTU/hr per bore foot, depending on soil conductivity and system run time.
Question 6: What is the purpose of a pressure/temperature (P/T) port on a ground loop header?
- To add antifreeze solution to the loop
- To measure entering and leaving water conditions without draining the system (Correct answer)
- To release excess loop pressure during thermal expansion
- To connect the loop to the domestic hot water desuperheater
Correct answer: To measure entering and leaving water conditions without draining the system
P/T ports allow technicians to insert probes and read pressure and temperature data for diagnostics without breaking the sealed loop.
Question 7: Which heat pump refrigerant cycle component is responsible for raising the refrigerant pressure before it enters the condenser?
- Expansion valve
- Evaporator
- Compressor (Correct answer)
- Filter-drier
Correct answer: Compressor
The compressor increases refrigerant pressure and temperature, enabling heat rejection at the condenser.
CRD Ground Loop & Heat Pump Configuration 2
What is the primary reason a designer would choose a slinky horizontal ground loop over a straight horizontal loop?