CRD Ground Loop & Heat Pump Configuration 3

Question 1

When designing a multiple-bore vertical loop field, what is the minimum recommended bore spacing to prevent thermal interference?

Accepted Answer

20 feet

Answer

IGSHPA guidelines recommend a minimum of 20 feet between vertical bores to limit long-term thermal interference and ground temperature change.

Question 2

A geothermal heat pump system has a COP of 4.0 in heating mode. If it delivers 48,000 BTU/hr of heat, how much electrical power does it consume?

Accepted Answer

3,517 W

Answer

Power = Output/COP = 48,000 BTU/hr ÷ 4.0 = 12,000 BTU/hr input; converting: 12,000 / 3.412 ≈ 3,517 W.

Question 3

Which grout characteristic is most important for optimizing vertical bore thermal performance?

Accepted Answer

High thermal conductivity

Answer

High thermal conductivity grout reduces borehole thermal resistance, allowing more efficient heat exchange between the pipe and the surrounding formation.

Question 4

In a two-stage geothermal heat pump, what is the primary advantage of first-stage operation at partial load?

Accepted Answer

It improves efficiency by operating the compressor at a lower compression ratio

Answer

At partial load, the first stage runs at a lower compression ratio, yielding higher COP because the temperature lift between source and load is reduced.

Question 5

What does the term 'ground thermal conductivity' (λ) describe in loop field design?

Accepted Answer

The rate at which soil or rock transmits heat per unit thickness

Answer

Thermal conductivity (W/m·K or BTU/hr·ft·°F) describes how readily a material transfers heat, directly affecting bore length calculations.

(CRD) Certified Residential Geothermal Designer Practice Test

(CRD) Certified Residential Geothermal Designer Practice Test

CRD Ground Loop & Heat Pump Configuration 3