CRD Geothermal System Controls, Electrical & Auxiliary Components 1 — Questions and Answers
Question 1: Which type of thermostat is most recommended for geothermal heat pump systems to prevent unnecessary auxiliary heat activation?
- Single-stage manual thermostat
- Two-stage thermostat with intelligent recovery (Correct answer)
- Standard programmable thermostat without staging
- Outdoor temperature-only reset thermostat
Correct answer: Two-stage thermostat with intelligent recovery
Two-stage thermostats with intelligent recovery gradually bring the space to setpoint using only the heat pump, avoiding premature activation of auxiliary resistance heat.
Question 2: What is the primary function of a desuperheater in a residential geothermal heat pump system?
- Remove excess heat from the compressor housing
- Pre-heat domestic hot water using waste heat from the refrigerant cycle (Correct answer)
- Regulate entering water temperature in the ground loop
- Reduce electrical consumption during utility peak demand periods
Correct answer: Pre-heat domestic hot water using waste heat from the refrigerant cycle
A desuperheater captures high-temperature waste heat from the refrigerant before it reaches the condenser and uses it to pre-heat domestic hot water at no additional energy cost.
Question 3: In a geothermal heat pump system, what does an auxiliary heat 'lockout' control primarily accomplish?
- Prevents the heat pump from running when outdoor temperatures exceed 65°F
- Prevents backup resistance heat from activating when the heat pump can adequately handle the load (Correct answer)
- Locks out the ground loop pump when loop temperatures are too high
- Prevents the system from operating during utility demand response events
Correct answer: Prevents backup resistance heat from activating when the heat pump can adequately handle the load
An auxiliary heat lockout control inhibits backup resistance elements from energizing whenever the heat pump is capable of maintaining comfort, preserving system efficiency.
Question 4: What is the purpose of a flow center in a geothermal ground loop system?
- To control refrigerant flow rate inside the heat pump
- To house the circulating pumps and provide a service/purging point for the ground loop (Correct answer)
- To distribute conditioned air evenly through the duct system
- To monitor and log electrical power consumption of the system
Correct answer: To house the circulating pumps and provide a service/purging point for the ground loop
A flow center contains the ground loop circulating pumps, isolation valves, and purge ports, providing a single service location for the hydronic ground loop.
Question 5: Which control strategy improves geothermal heat pump efficiency by varying compressor output to match the actual heating or cooling load?
- Two-position on/off compressor control
- Variable capacity or variable speed compressor control (Correct answer)
- Time-of-day scheduling with fixed capacity
- Outdoor air reset of leaving water temperature
Correct answer: Variable capacity or variable speed compressor control
Variable capacity compressors modulate their output to closely match the building load, reducing cycling losses and improving overall system COP.
Question 6: What voltage supply is most commonly used for residential geothermal heat pump compressors in the United States?
- 120V single-phase
- 208/230V single-phase (Correct answer)
- 277V single-phase
- 480V three-phase
Correct answer: 208/230V single-phase
Residential geothermal heat pumps in the US are designed for 208/230V single-phase power, which is the standard service voltage available in most homes.
Question 7: What is the primary benefit of adding a buffer tank (or hydraulic separator) to a hydronic geothermal heat pump system?
- It stores excess ground loop antifreeze for seasonal use
- It adds thermal mass to prevent short cycling of the heat pump compressor (Correct answer)
- It filters sediment and contaminants from the loop fluid
- It balances electrical load across the three phases of service
Correct answer: It adds thermal mass to prevent short cycling of the heat pump compressor
A buffer tank provides thermal mass between the heat pump and the distribution system, ensuring the compressor runs for adequate minimum on-times and preventing short cycling.
CRD Geothermal System Controls, Electrical & Auxiliary Components 1
Which type of thermostat is most recommended for geothermal heat pump systems to prevent unnecessary auxiliary heat activation?