Variable-speed Features Enhance Geothermal Performance
Strides in speed-control technologies improve comfort and efficiency
Geothermal heat pumps (GHPs) have been around for a long time, but recent technological advances have propelled these systems into a new sphere of efficiency and comfort, said Doug Dougherty, president and CEO of Geothermal Exchange Organization (GEO). “If you look back 10 or 15 years, COPs [coefficients of performance] of 3 or 3.3 were considered cutting-edge for geothermal systems; now, they’re 5 and above on many units.”
As for comfort, variable-speed technology has been a game changer. Just about every moving part within a GHP now has variable-speed capabilities, noted Dougherty. “The variability of the machine allows it to ramp up to a point where it can satisfy heating or cooling demand and then ramp down for shoulder months, which improves comfort and makes the equipment even more efficient.”
Variable-speed technology plays a prominent role on WaterFurnace Intl. Inc.’s 7 Series water-to-air GHPs, which feature a compressor that is driven by a variable-frequency inverter. This allows system capacity to be modulated to match the heating or cooling load with modulation as low as 20 percent of capacity. The blower motor and pump module also feature variable-speed capabilities and are modulated to match the system’s capacity output.
“Since system capacity is modulated to match the heating or cooling load, it provides homeowners with the ultimate in comfort and performance,” said Chris Mann, director of residential product engineering for WaterFurnace. “The system runs much of the time at greatly reduced output capacity, which is where the heat pump efficiency is at its highest and keeps operating costs to a minimum. This also increases comfort since homeowners won’t experience temperature swings as they would with other types of heating and cooling equipment.”
Variable-speed capability also reduces wear and tear on components because the compressor and blower motor are ramped up to speed slowly to reduce torque on internal components. As a result, the 7 Series can run longer with fewer stops and starts.
Enertech’s new variable-speed water-to-water product line — available later this year — will feature a variable-speed compressor, inverter drive, and variable-speed internally mounted pumps. The pumps circulate closely monitored fluids on both source and load sides to deliver the required flow and temperatures needed to ensure high efficiencies. “The result is accurate control of the source- and load-side heat exchanger temperatures and pressures for increased efficiency as well as increased compressor reliability,” said Dan Jackson, vice president of operations at Enertech.
These new variable-speed units can determine when a home does not require full capacity and adjust the unit’s output to match the need, providing greater efficiency, comfort, and reliability, explained Jackson. “This also allows our units to more effectively control humidity levels while dramatically lowering the cost of operation. The combination of variable-speed technology along with the comfort of a water-to-water system gives end users the best of both worlds.”
ClimateMaster Inc.’s variable-speed Trilogy® 45 Q-Mode® is certified by Air-Conditioning, Heating, and Refrigeration Institute (AHRI) to exceed 45 EER. It features four modes of operation: a cooling mode, a heating mode, a mode dedicated to heating water, and a cooling mode that rejects heat to the hot water tank, which increases its efficiency even more. The variable-speed loop pump is also internal, saving time at installation.
EarthLinked’s variable capacity refrigerant management system monitors the amount of heating or cooling capacity needed by the home and allows only that precise amount to be used in the system at any given time. “We’ve matched our variable capacity refrigerant management system with a state-of-the-art real-time diagnostic and monitoring system that is designed to give the homeowner optimal comfort and reliability with exceptional efficiency. It also offers technicians a simple, efficient, and effective tool to reduce installation time and increase the response effort to any maintenance requirements in the future,” said Joe Parsons, COO of EarthLinked.
This Web-based diagnostic and monitoring system is new to EarthLinked units this year. It continuously monitors critical temperatures, pressures, power consumption, and run times of the system, along with other data points to measure comfort and performance. “Designed exclusively for technicians and installers, the Web portal allows dealers to monitor their portfolio of installed EarthLinked geothermal systems at a glance from a simple website. Onboard Bluetooth communication allows a technician to monitor the system in real time with better accuracy than an analog gauge set.”
A popular feature on most Bosch Thermotechnology units is the hot water heat-recovery package, which provides domestic hot water while the unit is running in both heating and cooling modes. In addition, the company’s Smart Start kit, offered on its Greensource™ SM Series two-stage product, reduces inrush currents at compressor startup, which reduces wear and tear on the compressor. The company is planning to introduce a new heat pump controller and communicating thermostat control to the geothermal market later this year.
“These features are designed to improve unit performance, reliability, and maintenance,” said Joshua Samp, product manager, Bosch Thermotechnology. “The Smart Start option reduces compressor maintenance needs while the heat pump controller and communicating thermostat improve the installation, service, and troubleshooting experience. Adjustable unit settings, real-time unit operating conditions, a service mode allowing control of thermostat calls, unit lockout history, and a snapshot of unit operating conditions prior to a lockout will all be available through the new heat pump controller.”
Enertech’s new variable-speed water-to-water product line features high-temperature hydronic output that can supply radiant floor heating, forced-air heating and cooling, domestic potable hot water, pool heating, and ice melting systems. “Fossil fuel hydronic systems are generally designed to operate at higher temperatures, and our new product line is designed to work with these systems,” said Jackson. “The high-temperature hydronic output allows for less heat surface area for radiant system layout and planning and also allows for drop-in replacement or upgrade for boiler-type systems.”
ClimateMaster’s intelligent residential geothermal heating and cooling system features advanced monitoring and diagnostics. Web-enabled configuration and diagnostics allow dealers to access the Trilogy product obtaining real-time data information. The iGate™ Connect Smart Thermostat allows homeowners to monitor performance, perform tasks like changing set points, program schedule changes, and set reminders and alerts from anywhere via an Internet-connected computer, smartphone, or tablet.
In addition to variable-speed technology, WaterFurnace’s 7 Series water-to-air GHPs feature the Aurora communicating controls platform, Symphony home comfort platform, and IntelliZone2 communicating zoning system. The Aurora controls platform is a modular controls system that communicates via the Modbus protocol. It is configured to connect to devices, such as a communicating thermostat as well as the Aurora Interface Diagnostic Tool (AID tool), which simplifies system setup and troubleshooting. Symphony is a Wi-Fi-based Web-enabled home comfort system that provides the tools necessary to control the system from any Internet-connected smartphone, tablet, or computer.
The IntelliZone2 communicating zoning system communicates via Modbus to the thermostats and Aurora controls in order to estimate zone demand and deliver the proper amount of airflow to achieve the desired comfort level. Each zone is controlled by its own space thermostat and damper motors, which are operated from the relay board. “All these options help improve service while not making the installation any more difficult,” said Mann.
Dougherty contends that GHP technology will continue to advance, resulting in even greater efficiencies and better comfort. “There is no technology out there that can compete with GHPs in terms of efficiently satisfying the thermal load of a building. If you’re serious about demand reduction, energy efficiency, renewable energy, or comfort, then GHPs are really the best answer.”
Publication date: 2/15/2016