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As the popularity of geothermal systems (i.e. ground source heat pumps (GSHPs), also known as geothermal heat pumps (GHPs)) increases, more and more home and property owners are trying to determine whether these systems are right for their property.
A major question that we keep hearing from potential consumers is – what is the best type of ground heat exchanger (or ground loop)?
The short answer is: ALL of them!
Or perhaps we should say: It depends!
To better understand what we mean, however, let’s first look at what a ground loop (also known as a ground heat exchanger) is and then at what different types of ground loops are available.
What is a Ground Loop / Ground Heat Exchanger?
The ground loop, or ground heat exchanger, is the part of the geothermal heat pump system that is the heat source/sink for the energy being transferred to and from the indoor heat pump.
In other words, the ground loop is the part of the system that gathers the heat from the ground and carries that heat to the heat pump OR the part that conveys the heat from the building back into the earth. It is the part of the system that does the actual collecting and conveying of the heat.
There are three main parts to the ground loop:
- the sealed piping system, usually made of high-density polyethylene (HDPE) plastic piping
- a liquid mixture of water and antifreeze solution that conveys the heat through the piping
- small circulator pump(s) which induce fluid circulation and fluid through the pipes in the ground
The above parts are common in all ground loop heat exchangers regardless of their type or design. And all heat exchangers, despite their specific design, carry out the same function through these parts.
That said, there are four different main types of ground loops to choose from.
However, which will be best for your property will depend on multiple factors unique to the property.
What Factors Determine Which Ground Heat Exchanger Will Work Best?
When trying to choose the best ground loop design for your home or property, the following factors will need to be considered:
- Available footprint: a rural property with lots of space will have different options than a home in a historic downtown setting with small land availability and restrictions.
- Soil type: the type of soil and rock formations on the property may play a role in the choice of the best ground loop for your property.
- Availability of water: the presence of adequate, quality ground water, or a nearby lake, pond, or even stream, may influence the
bestground heat exchanger selection for your property.
- Loop contractor types which are available to serve the geographic area, as well as their installation rates.
Ultimately, each property site will have some limitations and unique characteristics that will determine which kind of ground loop will work best.
What are the Types of Ground Loops Available?
As stated briefly above, there are four main types of ground loops / heat exchangers:
- Vertical Ground Loop: a vertical ground loop requires deep, vertical holes, typically between 4.5” to 6” depending on whether it is residential or commercial, to be bored into the ground.
Each bore hole has one pipe descending the hole, a U-bend at the bottom, and a pipe ascending back up and reconnecting to the loop. Bore hole depths typically range between 150 to 500 + feet (depending on the soil type and space allowed).
Vertical ground loops are the most compact, requiring approximately one vertical bore/circuit per ton. A residential system may only require two or three bores. Thus, these tend to be the systems most suited for city and compact residential areas.
However, due to the depth of the bore holes, a special drill rig may be required, which may result in a slightly higher costs than other systems, even though less piping and area must be used.
- Horizontal Ground Loop: a horizontal ground loop is more spread out and does not go as deep.
Rather than deep vertical bore holes, one or more trenches are dug, depending on the loop piping configuration, by a backhoe, trencher, bulldozer, or similar machine.
Multiple trenches will be required, depending on the soil type, and space allowed. The piping will be laid in long, horizontal loops within these trenches.
Horizontal ground loops do require the most space, and usually more piping.
Horizontal heat exchangers are better suited for places with large space availability.
- Surface Water Loops: when a privately owned body of water exists on the property, a surface water loop may be the best option.
The water does need to be close – no more than 300 feet away. It also needs to be about ½ to ¾ of an acre in size for a typical residential application. Furthermore, if it is a pond or lake, it should be at least 8 to 10 feet average depth, even during the dry season.
With surface water loops, the sealed piping loop (or heat exchanger loops) will be submerged beneath the surface of the water. These systems must be closed loop, which means none of the pond/lake/river water should flow directly through the pipes, as this could damage the equipment.
Stagnate bodies of water, like lakes and ponds, are better than flowing water in climates that are heating dominate.
- Open Loop: also called the ground water system, or “pump and dump,” an open loop system is a possible option when high quality ground water is available.
In this system, rather than the piping forming a sealed loop, the well water is used directly as the fluid within the piping, thus why it is called “open,” and conveyed to the indoor heat pump, then “dumped” in a nearby pond, lake, stream, or
In essence, one end of the open loop sucks up the well water, uses it for the heat transfer process, and then sends the used water into an approved, nearby return water location. This is why the quality of the ground water matters, as poor water quality will result in more maintenance requirements and potentially shortened equipment lifespan.
For an open loop system, the groundwater source well must be prequalified by a well water specialist to ensure it will have a good volume year-round to meet the peak water demand and usage on the well along with good quality water beforehand.
A proper return water disposal area must be available, and it should be noted that some jurisdictions do not allow open systems at all.
It should be stated that even at its best, with high water quality and volume available, the nature of the open loop does suggest it will likely have more maintenance requirements than closed loop systems.
So, Which Ground Loop System is Best for Your Application?
So, regardless of the specific design, all heat exchangers / ground loops perform the same function when designed properly and installed correctly.
Ultimately, then, the answer to the question is: the heat exchanger that has a design ideally suited to your available property, which supplies the total BTUs needed to efficiently heat/cool your home/building, is cost effective to purchase, and which operates within the manufacture’s design limits, while providing years of operation with minimal maintenance needs.
Every property will have its unique resources and limitations which must be considered in the design of the heat exchanger.
All things considered; this means it will be vital that you do your research to ensure the best ground loop heat exchanger for your property will be installed.
Find contractors who have staff with proper geothermal heat pump system design training and who work with a quality supplier/manufacturer and who provide excellent consumer support. These individuals will know all the factors which should be considered in the design of your loop and will be able to design and properly install an excellent ground heat exchanger for your geothermal heat pump system.
Have questions or need help finding a contractor you can trust to help design the best system for your property?
Visit our website’s directory to see a list of businesses and contractors that are a part of our vast IGSHPA network: Business Directory | International Ground Source Heat Pump Association (igshpa.org).