The earth’s surface is an enormous sponge that is constantly absorbing heat energy from sun. This solar energy is stored in the ground under our feet and in our backyards. Within 10,000 meters of the earth’s surface, this heat contains 50,000 times more energy than that which is found in all oil and gas resources combined. Geothermal HVAC systems use this energy source to power your home’s heating and cooling systems. A loop – or series of pipes – carries a fluid that is used to connect the system’s heat pump to the earth and harness the energy contained within.
Types of Loop Systems
There are two types of loop systems: closed and open. Open loop systems in our geographic location tend to be more problematic due to poor groundwater quality. That’s why we traditionally recommend closed loop systems. All loop systems are created equal and no one loop is better than another as long as it gives you the required heat transfer in the ground. Loop type doesn’t matter: Horizontal or vertical, slinky or straight pipe, these loops are equal because they’re designed to be equal. The best loop is the loop that fits your needs and budget.
Closed loop systems are the recommended installation method in our area. In this type of system, water or a water and antifreeze solution is circulated through a buried pipe. The length of the pipe depends on a variety of factors, including the ground’s thermal conductivity, temperature, and moisture levels. When installed properly, closed loop systems are efficient, economical, and reliable.
In an open loop system, groundwater is drawn up from one well via an aquifer which passes the water through the heat pump’s heat exchanger and is finally discharged to the aquifer through a second well that is located a short distance from the first. For an effective heat exchange, generally 2-3 gallons per minute per ton of capacity are necessary. Because the temperature of groundwater is nearly constant throughout the year, open loop systems are a popular option in areas where they are allowed and have been used successfully for decades. However, there are a number of challenges associated with open loop systems:
- The chemical conditions of some local groundwater sources can foul the heat pump’s heat exchanger. In these situations, extra precautions may be needed to keep gasses in solution in the water source.
- Water use and discharge methods must be cleared with local officials in order to ensure compliance with environmental regulations and concerns. Increasing environmental concerns mean that local officials must be consulted to ensure that you are in compliance with all regulations concerning water use and accepted water discharge methods. It’s rarely acceptable to discharge wastewater to a sanitary sewer system.
For small installations where there is adequate land available, horizontal loops are usually the most cost-effective option. In this type of system, up to 6 pipes are buried in trenches in parallel connection with at least one foot between pipes and 10-15’ between each trench. Slinky-style loops are also very common.
In many situations, vertical closed loops are the preferred solution because of the spacing requirements for horizontal loops. For example, many schools and commercial buildings rely on vertical loops because a horizontal loop system would simply require too much space. Vertical loops can also be used in areas where the soil depth prohibits trenching. Depending on the conditions of the ground, the length of the loop can vary between 200-400’ of vertical drilling.
There are two styles of vertical drilling that are used in our area. Air rotary drilling utilizes high pressure air to drill through hard rock structures and is commonly used in areas west of route 95. Mud rotary drilling uses recirculated high pressure water to drill through mud, sand, clay, and gravel and is generally used east of 95.
Pond loops are a type of closed loop system that takes advantage of an existing pond or stream. If the body of water is deep enough and has enough flow, then a system of closed loop coils can be placed on the bottom of the pond. Fluid is then pumped as with a conventional closed loop ground system. Pond loops have not been shown to damage nearby aquatic systems and they are an economical option when the conditions are suitable.
Contact Ground Loop Today
At Ground Loop, we’re the premier providers of horizontal, vertical, and pond loop systems in the Maryland region and we have the experience and knowledge needed to build the right system for your needs. To learn more about what we can do for you, give us a call today at (410) 836-1706 and request your free, no-obligation estimate.
(Thank you to the Geothermal Heat Pump Consortium for the information contained on this page and the vapor compression cycle diagram. © Copyright 1995, 1996, 1997 by Geothermal Heat Pump Consortium, Inc. Used with permission.)