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A GXS draws heat from the earth. Burying a ground loop for a GXS requires excavation around your home. Other services are usually buried in the ground already, including electrical cables, water lines, sewer lines, septic fields and gas lines, that must be avoided when you dig. There may be trees and shrubs that you would prefer not to disturb. On a smaller property, it may be impossible to get to the best possible site with heavy equipment like a backhoe or large, truck-mounted drill rig.
Sometimes there are alternatives. Contractors in some areas specialize in the installation of earth loops on smaller lots. In some areas, it may be possible to drill boreholes deep enough to cause only minimal disturbance to a yard, or drill the boreholes with a compact drill rig that can reach the site easily. A chain trencher may be small enough to fit into the backyard.
Make sure you know the type of equipment the contractor is planning to use, and that both you and the contractor understand exactly where the loop will be located. Many contractors will mark the location of the earth loop with small flags or spraypaint markers on the ground.
Tell the contractor about any landscaping features you want to protect. Before work begins, answer the following questions: Who will be responsible for final landscaping work after the loop is completed? Will the contractor be installing the loop, or will the work be sub-contracted? If the work is done by a sub-contractor, will the contractor be at the site when the loop is installed? Will the contractor guarantee the installation?
One of the benefits of a GXS is its low power demand. Although it is often possible to install a system in an existing home without upgrading the electrical service, you must verify that this is the case. If you are replacing an electric heating system, your existing electric panel will probably be adequate. If you are replacing a fossil fuel furnace, however, you may well need to upgrade your service to accommodate a GXS, especially if you include an electric auxiliary heater in the system.
Most electric or fossil fuel furnaces designed for residential use in the past were intended to raise the temperature of the air circulating through them by 20–30°C. This was done to reduce the airflow needed to deliver heat to your home and minimize the ductwork size (and cost). Heat pumps in a GXS typically are designed to raise the air temperature by only about 10–15°C. Because of this, you have to move more air through your ducts if your new GXS is to deliver the same amount of heat to your home.
Your contractor may recommend changing some of the ductwork in an existing home to accommodate the greater air flow you need. This will make the system more efficient and reduce potential air noise problems. The contractor also should recommend lining the supply air and return air plenums with acoustic insulation, and installing flexible connections in the plenums connecting the heat pump to the ductwork system.
As noted above, you must do a thorough check into the location of underground services around your home. In addition, you should do a survey to find where your property lines are, as well as the positioning of easements and required property setbacks. Your neighbours’ domestic water wells may be affected. Similarly, your neighbours’ wells may affect the performance of your open-loop GXS.
The installation of the earth loop for a GXS will always cause some disturbance to the landscaping around your home. A horizontal loop will require significantly more excavation than other types of loops, although any loop installation will require some digging around your home. The repairs to the landscaping take time, because the earth takes time to settle back into the trenches. The length of time depends to some extent on the type of soil on your property. Heavy clay soils tend to take longer to settle than looser, sandier soil.
In some soil conditions, the contractor may recommend that the dirt remain mounded over the trench for several months, or even for the winter. The dirt will settle as the rain soaks the trench over time or the spring runoff breaks down the larger clumps of earth. If the extra earth is removed, there probably will be some settling, which will result in a dip in the lawn wherever the trenching was done. The results are generally better if the earth is allowed to settle naturally.
You can speed up the soil settling by compacting of the soil every 10–20 cm as the trench is backfilled, although the labour cost can be high. Soaking the soil in the trench can accelerate the settling process as well.
Once the soil has settled, there will be nothing on your lawn to show that a ground loop is buried on your property.
Make sure your GXS is designed so as not to disturb trees, walls, overhead wires and other landscaping features. Allow space for the trenching or drilling equipment as well as the excavated soil. No part of your system or the coil you dig up should cross a property line without the written approval of your neighbour. Also, make sure you avoid crossing other underground services, like gas and water mains, telephone lines, power cables, sewer lines and drains, and protect them from damage or freezing. An earth loop must never be placed under a septic tank or cross the septic system’s drain.
In general, GXS piping should be placed well away from other services to avoid damage during repair operations.
When the earth loop installation is complete, the CSA standard states that you should make a map pinpointing its location. The simplest method of mapping the earth loop is to measure each significant point of the loop (such as the boreholes and the end of a trench) from two separate, permanent landmarks. For example, you can plot the location of a borehole from two corners of your home; this creates a triangle between the two points and the borehole, and makes it easy to find later. A map like this will be valuable when you (or possibly a future owner) want to make landscaping changes, such as installing a decorative fountain or planting a tree. The map should be placed in an envelope attached to the heat pump or some other safe place. If you are considering the purchase of a home with a GXS already installed, ask for a map or diagram of the loop system.A tracing wire or tape should be laid in the trench above the pipe, so the loop can be located with a metal detector. A wide foil tape can also be laid in
the trench on top of the pipe, to show that something is buried underneath.