Geothermal Upgrade for Southface By Christopher Theal, Southface Despite a number of sub-freezing nights this winter, the new Water Furnace brand geothermal heat pump system at Southface hardly minds the outdoor temperature and seems to effortlessly keep us comfortable year round.

Kenny Libby, Manny Cromartie, Tom Niesse & Brian Copeland are pictured at the EarthCraft House builder recognition breakfast. Water Furnace, along with 50 additional exhibitors will be showing their wares at the Greenprints Green Tradeshow. More info at www.greenprints.org.

A geothermal heat pump uses a compressor driven refrigerant cycle (like all air conditioners, refrigerators and heat pumps) coupled to underground water circulation pipes to provide warmth in winter and cooling in summer. Tapping into underground earth temperatures ensures a constant, comfortable energy source, regardless of the outdoor weather. Conventional air-source heat pumps have a nearly impossible task trying to extract heat from the ambient environment as temperatures approach freezing: they usually compensate with electric resistance ‘strip heat’ or a back-up gas furnace (dual fuel systems).

In the summer of 2007, our original ground-source (geothermal) heat pump unit suffered an irreparable compressor failure, just in time for some of the hottest weather on record for Atlanta. Since that unit was 11 years old, and much better equipment had become available, we inquired of Water Furnace regional manager Tom Niesse about more efficient solution. Tom has been a good friend to Southface since well before I came to work here years ago, and he was able to provide us with a truly generous gift in our time of need—a top of the line Water Furnace Envision heat pump.

The new heat pump boasts some remarkable capabilities compared to our older unit. The efficiency rating of geothermal heat pumps is generally superior to other heating and cooling options, but the Envision series optimizes this performance with a variable speed blower and compressor that allows for a ‘soft start’ at the beginning of each heating or cooling cycle as well as extra slow-running cycles for prolonged dehumidification. The different operating speeds can simplify ductwork zoning by reducing or eliminating the need for large bypass dampers when only one zone calls for conditioning. Additionally, the refrigerant is not ozone-depleting in the event of a leak. Like many geothermal heat pumps, this Water Furnace contains a built-in desuperheater, which captures waste heat during the cooling cycle in order to supplement domestic potable water heating.

For new geothermal installations, the ground loops are typically configured in a vertical or horizontal orientation. Drilling vertical bore holes is more expensive, but is usually the only option on small lots. The easiest installations, by far, make use of a nearby pond or lake which serves as both heat source and sink.

In anticipation of the new unit’s arrival at Southface, we were put in touch with Ken Libby and Brian Copeland of Geothermal Energy Solutions, an outfit that exclusively deals with ground-source heat pumps, particularly from Water Furnace. Brian was the primary technician who supervised our installation, and he was a pleasure to have in the office. Our existing underground plumbing loop was intact and trouble free, so it was a relatively easy operation to connect, program and test the new heat pump. A circulating loop water pump failure (also 11 years old) was the only real bump in the road, and that was easily replaced with spare parts. The Water Furnace has operated flawlessly through last summer and fall, and now through a surprisingly chilly Atlanta winter.

At Southface, we are keenly aware of the environmental consequences of residential and commercial space conditioning, not to mention the steadily increasing financial burden of energy utility rates. Geothermal heat pumps are among the most efficient space conditioning devices available, though they have a higher equipment cost than more conventional options. The payback time for this extra cost will vary case by case, but the superior indoor comfort and positive cash flow from lower utility bills begin immediately. Because of its thrifty energy consumption, geothermal heat pumps generate the least CO2 and air pollution of any mechanical HVAC system commercially available. Environmental benefits and cost savings can be further increased with the incorporation of passive solar architecture and a conservation-minded lifestyle.

No system in the home operates without affecting several others. This is especially relevant to HVAC, since a tight, well-insulated home requires a smaller system than typical rules-of-thumb might suggest. Smaller HVAC equipment costs less to buy and less to operate. The Southface ‘house as a system’ strategy has always addressed airsealing and insulation of the building envelope first, before specifying the appropriate size and design for major mechanical systems. No matter the building, however, a geothermal heat pump is guaranteed to provide unparalleled operating efficiency and comfort.

For more geothermal information, please visit the websites listed below:

Water Furnace home page: www.waterfurnace.com

Geothermal Energy Solutions: www.geosaves.com

Geothermal Heat Pump Consortium: www.geoexchange.org

DOE Energy Efficiency and Renewable Energy: www.eere.energy.gov