Ground Loop & Heat Pump Configuration Flashcards

What is the function of the expansion device in a water-source heat pump refrigerant circuit?

Answer: It reduces refrigerant pressure to enable evaporation at low temperature

The expansion device (TXV or orifice) drops refrigerant pressure so it can absorb heat by evaporating at low temperature in the evaporator.

HDPE pipe used in ground loops must conform to which ASTM standard for pressure ratings?

Answer: ASTM D3035

ASTM D3035 covers HDPE pipe dimensions and pressure ratings for geothermal ground loop applications.

A loop field is described as 'thermally imbalanced.' What does this mean for long-term system performance?

Answer: Heating and cooling loads extract and reject unequal amounts of heat annually, causing ground temperature drift

Thermal imbalance occurs when annual heating and cooling loads differ, causing the ground to either warm or cool over years, reducing heat pump efficiency.

What minimum flow rate (gpm per ton) does IGSHPA typically recommend for closed-loop ground heat exchangers to maintain turbulent flow?

Answer: 1.5 gpm/ton

IGSHPA recommends approximately 1.5 gpm per ton to ensure turbulent flow regime and adequate heat transfer in ground loop piping.

Which antifreeze solution offers the best combination of freeze protection and low viscosity at operating temperatures for residential ground loops?

Answer: Propylene glycol

Propylene glycol is preferred for residential closed loops because it is non-toxic, biodegradable, and maintains acceptable viscosity at low temperatures.

What is the primary purpose of a flow center in a geothermal ground loop system?

Answer: To circulate loop fluid, maintain pressure, and allow fluid addition or purging

The flow center houses the circulator pump(s), purge valves, and fill ports needed to maintain proper loop fluid circulation and pressure.

In a variable-speed geothermal heat pump, what sensor signal most commonly modulates compressor speed?

Answer: Loop entering water temperature

The entering water temperature (EWT) from the ground loop is the primary control signal that tells the variable-speed compressor how hard to work.