How to Install Geo Thermal HVAC

Dig a series of 8 parallel trenches with the backhoe, each one 50 feet long, 1 foot wide and the greater of 4 feet deep or the depth needed to be below the frost line. Space trenches 5 feet apart. Dig the trenches perpendicular to the house wall. Dig a trench at the back of the trench field, which is the side closest to the house, to connect all the parallel trenches . At the opposite side of the trench field, dig out a connector with the shovel at every other parallel trench to form a continuous zig-zag trench.

Dig a trench to the foundation wall from a back corner of the loop field closest to the point in the house where the geothermal heat pump will be installed. Drill two 2-inch holes a foot apart through the foundation wall for passing the ground loop pipes into the house.

Pass two feet of the 1.25 inch high density polyethylene pipe through one of the foundation holes into the house, starting at the foundation. Lay the flexible pipe in the bottom of the trench, following the zig-zagging line of the trench. Splice pipe lengths in the trench as needed, using a polyethylene pipe fusion splicing device that forms an unbreakable watertight joint. Run the pipe back to the second hole in the foundation. Pass the pipe through the hole so that 2 feet of pipe is inside the foundation.

Test the piping with compressed air to check for leaks. Clamp an air chuck at one end of the pipe and a pressure gauge at the other end. Pump in air with the air compressor to 25 psi of pressure. Apply soap solution to each joint to check for leaks. Watch the pressure gauge for 30 minutes. The pressure shouldn’t drop.

Set your heat pump on a base as directed by the manufacturer. Select an accessible interior location where you can make connections to the ground loop piping, electric power and your house heating ductwork. The heat pump should be sized for your house and climate. Connect the ground loop circulating pump to one end of the ground loop and to the heat pump’s ground loop return pipe. Connect the other end of the ground loop to the ground loop supply pipe on your geothermal heat pump. Make the pipe connections using the method specified by the heat pump and circulating pump manufacturers.

Connect your home heating ductwork, electric supply line and thermostat wiring to your heat pump according to manufacturer directions. Connect an electric supply line to the loop circulating pump as specified by the manufacturer. Call local authorities for final inspection of your pipe, wiring and duct installations. Perform any additional tests required for local approval.

Backfill your trenches with soil. Fill in the soil in 6-inch layers. Compact the soil thoroughly after each layer. Backfill evenly on both sides of the pipe until the pipe is completely covered. When backfill is within 18 inches of the trench top, lay down a strip of foil-backed underground utility locator tape along the length of the entire trench. Continue backfilling and compacting layers until your trenches are full.

Close the valves that isolate the ground loop from the heat pump’s heat exchanger. Open the heat pump’s loop purge valve and loop drain valve. Connect a purge pump to the purge valve and a drain hose to the drain valve. Run the purge pump to pump water through the loop. Keep the purge pump running until all dirt, debris and trapped air is removed and the water runs clear. Stop the purge pump and close the loop purge and drain valves.

Open the heat pump’s isolation valves. Top up the system with water until the heat pump’s heat exchanger is full. Start up the system. Allow it to run for at least 30 minutes to allow any trapped air bubbles to escape through the automatic air purge valve. Set your house thermostat to the desired room temperature.