Geothermal Heat Pump Equipment

Compressors

While the basic principles of geothermal heating haven't changed much in 50 years, the technology has, and that has made all the difference. By far, the biggest step forward has been in compressor technology. Until about 1990, all heat-pump and air-conditioner compressors had just one speed, and because every installation had to be sized to handle only a few extreme days, every system was, in a sense, oversized. As such, it was inefficient most days of the year.

This situation was remedied by two quite different improvements in compressor design, both 25 percent to 30 percent more efficient than previous technologies. The first is a 2-speed compressor that can idle along on mild days and rev up for extreme days. Because these compressors run more often, you'll also realize better humidity control during the air-conditioning season.

Almost simultaneously, scroll compressors came on the market. Scroll compressors are radically different in design–they use an orbiting coil instead of a piston–and boast a 30 percent improvement in efficiency. Because they have very few moving parts–and fewer still that make contact–they are built to last.

Geothermal Heat Pump Add-ons: Backup and Hot Water

Most compressor compartments also contain two add-ons -–a resistance-heat grid and a desuperheater.

Geothermal heat pumps in northern climates may need a little help on very cold days, and a small electric-resistance heater does the job. The added operating expense comes to about $30 to $40 a year. Though this may seem a net loss, it's really not. On-board resistance heat allows the pump and piping loop to be downsized slightly, which saves money.

A desuperheater is an auxiliary heat-recovery system that provides up to 60 percent of a home's domestic hot water. It's really just a second condenser located in the cabinet and connected to a standard electric water heater via a coaxial fitting. It delivers more heat in summer, but it helps in winter, too. The purchase price is a hefty $500, but again, the cost is misleading. Without a desuperheater, you'd need to install more underground piping to dissipate the extra heat. As you might expect, most units come with desuperheaters.

Geothermal Heat Pump Control Units and Thermostats

Both the thermostats and the control panels for these systems are electronic. The thermostat is able to sense temperature changes to .1 degrees F and activate the system when it senses only a 1 degree temperature drop. Because the human body can sense only a 2 to 3 degree difference in temperature, the system is always one step ahead in comfort.

The microprocessor in the cabinet does double duty. It sequences the startup so that less stress is put on equipment, and it also has a built-in fault sensor that can identify the cause of a malfunction. The system faults appear on the thermostat so minor problems can be corrected immediately and more serious problems are diagnosed before the service technician arrives.