CRD Geothermal System Design Principles 4

Question 1

What is the recommended minimum flow rate per ton of capacity for a residential closed-loop geothermal system using water as the heat transfer fluid?

Accepted Answer

1.5–3.0 GPM per ton

Answer

IGSHPA and equipment manufacturers recommend 1.5–3.0 GPM per ton to ensure adequate heat transfer and turbulent flow in the ground loop.

Question 2

A geothermal loop filled with 20% propylene glycol solution will have a freeze point of approximately:

Accepted Answer

15°F (-9°C)

Answer

A 20% propylene glycol solution has a freeze protection point of approximately 15°F (-9°C), providing a safety margin below typical minimum EWT targets.

Question 3

In a two-stage or variable-speed compressor geothermal heat pump, what design advantage does variable capacity provide for residential systems?

Accepted Answer

Better matches part-load demand, improving seasonal efficiency and comfort

Answer

Variable-capacity compressors modulate output to match the actual building load, reducing short-cycling and improving the system's seasonal COP and humidity control.

Question 4

Which loop configuration is most appropriate for a residential site with limited land area but access to deep drilling?

Accepted Answer

Vertical closed-loop boreholes

Answer

Vertical closed-loop boreholes require a small surface footprint because heat exchange length is achieved by drilling deep rather than spreading horizontally.

Question 5

What is the purpose of a 'header' in a closed-loop geothermal bore field?

Accepted Answer

It connects multiple parallel borehole loops to a common supply and return manifold

Answer

The header manifold connects individual borehole U-tubes in parallel, balancing flow distribution across the bore field and reducing total pressure drop.

(CRD) Certified Residential Geothermal Designer Practice Test

(CRD) Certified Residential Geothermal Designer Practice Test

CRD Geothermal System Design Principles 4