Designing Your Closed Earth Loop

A geothermal heat pump's earth loop installation is not just a matter of burying some pipes and hooking these pipes to your geothermal heat pump. Your earth loop must be matched to the home, and the geothermal heat pump, that it is coupled to. So, the first step in sizing an earth loop is having a correct Manual J heat loss heat gain calculation done. We need to know how many BTUHs your earth loop needs to supply to your geothermal heat pump, so it can heat your home correctly. This also tells us what the flow rate through your earth loop will have to be.

Next, we need to know about the soil that the earth loop will be buried in. How fast can it transfer heat through each lineal foot of the earth loop? To accurately determine your soil's thermal transfer rate, we need to know what your soil conditions are, including the type/s of soil (clay, sand, gravel, silt, top soil, and many others), and the moisture content of the soil. You will need to dig a couple of test holes so a soil analysis can be done. You can do this soil analysis yourself, with our instructions.

The soil properties, spacing of pipe, ground temperature, and BTUHs needed by your home, will determine how many feet of pipe will need to be installed in the earth.

Once we know how many feet of pipe the earth loop will need, we will decide how many individual loops to use, of what size pipe, so we can choose the best sized pump for your payback. We almost always use ECM pumps nowadays, as manufacturers have lowered their prices greatly, and made them simple to install, and extremely reliable.

Designing the earth loop is a balance between how much power the circulating pump will use because of the diameter of the pipe, and how much that diameter of pipe will cost. If the diameter of the pipe is small, it will be less expensive, but smaller pipe means higher pumping costs. On the other hand, if we use pipe large enough to install just one loop, the energy we save even with the smallest pump can't pay back the higher pipe cost. We figure out where your energy payback sweet spot is, so you save the most over time.

It is equally important for the geothermal heat pump, earth loop, and air ducting (or radiant heat piping) to be designed correctly.

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