CRD Geothermal System Design Principles 5

Question 1

What does EER measure in the context of a geothermal heat pump operating in cooling mode?

Accepted Answer

Ratio of cooling output (BTU/hr) to electrical input (watts) at a single rating condition

Answer

EER (Energy Efficiency Ratio) is the instantaneous cooling capacity in BTU/hr divided by electrical power input in watts at a specific set of rating conditions.

Question 2

What is 'borehole thermal resistance' (Rb) and why does it matter in loop design?

Accepted Answer

Thermal resistance between the circulating fluid and the borehole wall; higher Rb requires longer bores

Answer

Borehole thermal resistance (Rb) quantifies how difficult it is for heat to move between the fluid in the U-tube and the surrounding ground; a higher Rb means less efficient heat exchange and greater required bore length.

Question 3

When a geothermal system is designed with a 'hybrid' configuration pairing a ground loop with a cooling tower, what problem does this solve?

Accepted Answer

Cooling-dominated building loads that would thermally saturate the ground loop

Answer

A cooling tower (or fluid cooler) rejects surplus heat to the atmosphere in cooling-dominated climates, preventing multi-year ground temperature rise that would degrade heat pump efficiency.

Question 4

IGSHPA's block-load design method for residential systems requires knowing the design-month peak block load and the annual equivalent full-load hours. What are the annual hours used to calculate?

Accepted Answer

The annual ground heat exchange needed to determine long-term temperature penalty

Answer

Annual equivalent full-load hours convert the seasonal energy into an annual ground heat exchange quantity, which is used to compute the multi-year temperature penalty from load imbalance.

Question 5

What pipe material is most widely used for residential closed-loop ground heat exchangers in the US, and why?

Accepted Answer

High-density polyethylene (HDPE), for flexibility, chemical resistance, and heat-fused leak-free joints

Answer

HDPE is the industry standard because it withstands ground movement, resists corrosion and biological attack, and can be thermally fused to create joints with no mechanical fittings underground.

(CRD) Certified Residential Geothermal Designer Practice Test

(CRD) Certified Residential Geothermal Designer Practice Test

CRD Geothermal System Design Principles 5