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Index
FAQs
Reference
Fundamentals
Ground Water
(Open-Loop)
Systems
Environment
Equipment
Ground-Coupled
(Closed-Loop)
Systems
Special Considerations
Installations
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Horizontal Loops
 If sufficient land area suitable for drilling or trenching is available, then
horizontal loops may be the most economic. A horizontal system will use a
number of horizontal trenches. Piping system designs range from a single pipe, to
multiple pipes arranged vertically in a narrow trench to multiple pipes in a
wider trench. 
The ground heat exchanger may be either series or parallel piping. Each has
both advantages and disadvantages.
Series System
Advantages:
- Single flow path and pipe size
- Higher thermal performance per foot of pipe since a larger diameter pipe is
required
Disadvantages:
- Larger water or antifreeze volume of larger pipe,
- Higher price per foot of piping material,
- Increased installed labor cost,
- Limited length due to fluid pressure drop and pumping costs.
Parallel System
Fabricated from smaller diameter pipe (which is generally less costly),
special care must be taken in flushing to get all the air out of the piping loop.
Advantages:
- Lower cost pipe
- Less antifreeze required
Disadvantages:
- Special attention to assure air removal
- Attention to balanced flow, within plus or minus 5 percent, in each parallel
path is required
Examples:
Some examples, depending on system size, of typical horizontal ground heat
exchangers are:
- Single 1¼ to 2 inch pipe, series water flow, 350 to 500 feet per ton nominal
length, buried 4 to 6 feet deep
- Two-pipe using 1¼ to 2 inch pipe, series water flow, 210 to 300 feet of trench
per ton with 420 to 600 feet per ton nominal length, buried 4 and 6 feet deep
- Four layer using ¾ to 1 inch pipe with 1¼ to 2 inch headers, parallel water
flow, 125 to 200 feet of trench per ton with 500 to 800 feet per ton nominal
length, buried 6 feet deep with 12 inch spacing
Further information, pipe data, pressure drop information, and calculational
procedures are given in guides published by IGSHPA. Some heat pump manufacturers also have selection
software available.
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