CRD Geothermal System Design Principles 2

Question 1

Which parameter most directly determines the required length of a vertical bore field in a residential geothermal system?

Accepted Answer

Ground thermal conductivity

Answer

Ground thermal conductivity governs how efficiently heat transfers between the grout and surrounding soil, directly setting the required bore length per ton of capacity.

Question 2

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

Accepted Answer

Absorb fluid volume changes due to temperature fluctuation

Answer

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

Question 3

A designer uses a Ground Loop Heat Exchanger (GLHE) software tool and obtains a g-function. What does the g-function represent?

Accepted Answer

Dimensionless temperature response of the bore field over time

Answer

The g-function is a dimensionless thermal response factor that describes how the borehole field temperature changes over time under a unit heat pulse.

Question 4

What is the typical design entering water temperature (EWT) range for a residential heat pump operating in heating mode in a US northern climate?

Accepted Answer

32–40°F (0–4°C)

Answer

Northern climate ground loops are typically designed so that minimum EWT stays at or above 32–40°F to avoid freezing and maintain heat pump efficiency.

Question 5

Which heat pump rating condition is used by AHRI Standard 870 to certify residential geothermal water-to-air units?

Accepted Answer

EWT 50°F heating / 86°F cooling

Answer

AHRI 870 rates residential water-to-air heat pumps at 50°F EWT for heating and 86°F EWT for cooling as the standard certification conditions.

(CRD) Certified Residential Geothermal Designer Practice Test

(CRD) Certified Residential Geothermal Designer Practice Test

CRD Geothermal System Design Principles 2