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Geothermal loop options
- Doug Schuster
When you start considering a geothermal system for your home or business you will hear about several different loop options. One contractor will tell you his way is the best. A different contractor will claim that his way is the only way. You may know someone that had a vertical loop system. Maybe another friend has a horizontal bored loop. How do you get through all the information to find out what's best for you?
If you are building, your loop options are pretty straight forward. The construction process is going to clear any and all grass from your lot. The main questions tend to be simple ones. Do we have enough room to go with a horizontal system? Is it so rocky that we might have to go vertical? Can I use the pond out back? Should I go open loop?
Each loop option comes with different costs.
The first cost would be the installed cost. A vertical closed loop will be your most expensive option. Vertical loops are used when space is at a premium (city lot, too many trees, and commercial system) or rock makes it impractical to go horizontal. A horizontal closed loop would be significantly cheaper. These can be bored in similar to fiber optics and gas lines. They can be excavated with a track hoe or a rubber tire backhoe. They can be installed with a chain trencher. They can even be installed in large pits opened up with a bulldozer. These systems are quite a bit cheaper because they are not going as deep as a vertical loop and because the equipment is more readily available. Most contractors have excavation equipment; very few have a drill rig. The least expensive closed loop would be a pond loop. Provided you own a pond or lake that meets the requirements and is close enough, you can install a loop system in that body of water. The only real expense is the pipe and digging a ditch to the water's edge. On a side note; I wouldn't build a pond for the sole purpose of being your loop system. You might find the costs of building and upkeep are more than you bargained for. The least expensive of all systems is the open loop system, also known as "Pump and Dump". If you already have a water well, some states will allow you to install an open loop system. This is when you run the water from your well through your geothermal system and then dump it back into another well or body of water.
The second cost would operating and maintenance costs. Any of the closed loop system would have minimal maintenance costs, if any. And if they are designed and installed properly, there should be no difference in operating costs between a vertical, a horizontal, and a pond closed loop system. An open loop system is a different story. Since the water out of a well is always the same temperature, an open loop system will perform better than on a closed loop. With deep wells, the operation cost savings can often be eclipsed by the added cost of operating your well pump. Open loop systems also require periodic cleaning of the heat exchangers. Since a constant supply of fresh water means a constant supply of fresh minerals and other buildup, your heat exchanger will require professional cleaning from time to time. If you don't have it cleaned, the buildup will act as a barrier to good heat transfer and your unit performance will suffer.
If this is for an existing home you will want to consider your existing lawn and landscaping. Some of the loop systems mentioned above will make a huge mess of your yard while others will make less of a mess. If you have enough space, my favorite for an existing yard is a horizontal bored closed loop. Depending on space, soil conditions, and the ability to bore deep enough (around 15 to 20 feet), a horizontal bored loop system will not harm your existing landscaping. A horizontal bored system can even go under your house and other buildings, your driveway, your septic system, and anything else that might be in the way. A minimal area is excavated to connect the bores together and enter your house. Another style that causes minimal yard damage is a vertical closed loop. One thing that should be considered with an existing home is the cost of putting the yard back together. If a vertical system would have a smaller foot print but cost drastically more than a horizontal excavated system, you might find it cheaper to pay to have your yard landscaped and go horizontal.
The main points to remember is that it is OK to shop price on your loop system. If all closed loop systems perform the same given proper design and installation, why not go for the cheapest to install? I would do my homework and check out a few contractors. By talking to them you should get a good feel for why they are recommending a certain style loop system. Don't be afraid to ask for references. And by all means... call them! You can learn a lot from talking to their past customers.
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