Geothermal in Sackville

7-8 ft trenches dug in preparation to lay down PVC tubing.

m (7′) trenches dug in preparation to lay down PVC tubing.

The owners installed a 4.5 t (5 ton) geothermal system with horizontal tubing in 2007 when the two oil furnaces heating their large, older home were reaching the end of their lifespan. At that time, there were federal and provincial rebates available for homeowners who were installing geothermal systems. This reduced the overall cost of the installation to roughly $12000.

The owners opted for a horizontal geothermal field instead of a vertical field because it was both cheaper and their yard was spacious enough to fit the tubing needed for a 4.5-t (5-ton) system. The installers dug trenches 2 m (7′) deep in the yard, temporarily resulting in large mounds covering the lawn. They laid down over 150 m (500′) of trench and 600 m (2000′) of 5-cm (2″) PVC tubing. This is a closed system, and so the installers used propylene glycol (a much less toxic antifreeze solution than ethylene glycol).

The geothermal heat exchanger (left) and the plenum (right), as well as some duct work.

The geothermal heat exchanger (left) and the plenum (right), as well as some duct work.

Prior to installing the geothermal system, the owners underwent an energy audit to see where they could improve the energy efficiency in their home. They’d upgraded the insulation when they moved in, and after the audit they sealed leaks around the windows and in the stone-foundation basement. With several relatively simple modifications, the house’s energy score rose from about 50 to 74. The system was able to be tied into the existing ductwork, saving money and time spent on the conversion to geothermal.

The coolant in the pipes is warmed up by the earth and is pumped into the heat exchanger in the basement, warming the air in the plenum and pre-heating the water pumped into the electric water heater. The condensation formed inside the heat exchanger as a result of the warm air coming into contact with cooled pipes is drained via a pipe at the bottom of the heat exchanger unit. The water is drained into a sump, where a pump will remove excess if necessary.

Coolant pump controlling the flow of the coolant, propylene glycol, through the buried PVC pipes.

Coolant pump controlling the flow of the coolant, propylene glycol, through the buried PVC pipes.

The owners are very happy with their geothermal system and report that it keeps the house at a very comfortable temperature in the winter. Each morning, the pre-programmed thermostat gradually raises the house temperature so not to trigger the auxiliary heater. In the summer, the system functions as an air conditioner. They estimate that they were spending $3700 per year to heat their home, and that they would now be paying over $4000 per year with increases in fuel prices. The system has paid for itself in about 4 ½ years.

The owners have encountered very few issues with the system; one winter they noticed that the auxiliary electric heater kept turning on. The auxiliary heater should only turn on if the geothermal system cannot meet the temperature target set on the thermostat; ordinarily, this was never needed. Upon inspection, it was found that the pump that circulates the water in the heat exchanger had broken down. The replacement parts took 3–4 weeks to arrive, but there have not been any problems since then.

FHP (Florida Heat Pumps) heat exchanger.

FHP (Florida Heat Pumps) heat exchanger.

Geothermal condensation drain to sump

Geothermal condensation drain to sump

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