Download Applications Engineering Manual - EarthWise Intelligent Variable Air

System Design Variations
Drawbacks include:
•
Drilling costs are frequently higher than the trenching costs associated
with horizontal or spiral loops.
•
Grouting and backfilling of the boreholes require special attention to fill
material and to ensuring that the pipes and surrounding earth remain in
contact.
•
If the boreholes are spaced too close together, there is a potential for
long-term heat build-up in the ground that may be undesirable for a
cooling-dominated application.
•
Installation requires the knowledge and availability of a certified loop
contractor with proper drilling equipment.
Horizontal loops
Figure 90. Horizontal heat exchanger
Horizontal loops are often considered when adequate land is available
(Figure 90). Historically, horizontal loops often consisted of a single layer of
pipe buried in the ground using a trenching machine. However, land
requirements have been reduced with the advent of multiple-layer horizontal
loops. While less land and trenching is required, a multiple-layer loop
requires more total length of piping than a single-layer loop.
Each closed-loop pipe is placed in a trench, which is typically 6 ft (1.8 m) deep
and spaced 6 to 15 ft (1.8 to 4.6 m) apart. Trench length can range from 100 to
400 ft per “block” cooling ton (8.7 to 34.7 m/kW) for a single-layer loop.
Advantages of horizontal loops include:
•
Trenching costs are typically lower than the drilling costs associated with
vertical loop installation.
•
In cooler climates, horizontal loops may not build up as much heat over
time as vertical loops, because the pipes are closer to the surface, where
heat can be dissipated to the atmosphere.
Drawbacks include:
SYS-APM010-EN
•
Horizontal loops require a larger area of land than vertical loops.
•
At this shallower depth, ground temperatures are subject to seasonal
temperature variations, rainfall, and snow melting. Obtaining the same
loop temperatures as a vertical loop requires a more complicated design
with longer pipe lengths.
•
The longer pipe lengths also require more antifreeze solution (when
necessary) and more pumping energy than vertical loops.
•
The pipe is at greater risk of damage during backfilling of the trenches.
Water-Source and Ground-Source Heat Pump Systems
139