Bryant 50YEW Design Manual page 55

Part III: Source Side Design / Closed Loop Installation Guidelines
Pond/Lake Applications
Pond loops are one of the most cost effective applications of
geothermal systems. Typically 1 coil of 300 ft of PE pipe per cooling
ton [26 meters per kW -- one 92 meter coil per 3.5 kW of cooling
capacity] is sunk in a pond and headered back to the structure.
Minimum pond sizing is 1/2 acre [0.2 hectares] and minimum 8 to
10 feet [2.4 to 3 meters] deep for an average residential home.
In the north, an ice cover is required during the heating season to
allow the pond to reach an average 39°F [3.9°C] just below the
ice cap. Winter aeration or excessive wave action can lower the
pond temperature preventing ice caps from forming and freezing,
adversely affecting operation of the geothermal loop. Direct use of
pond, lake, or river water is discouraged because of the potential
problems of heat exchanger fouling and pump suction lift. Heat
exchanger may be constructed of either multiple 300 ft. [92
meter] coils of pipe or slinky style loops as shown in Figure 3-9. In
northern applications the slinky or matt style is recommended due
to its superior performance in heating. Due to pipe and antifreeze
buoyancy, pond heat exchangers will need weight added to the
piping to prevent fl oating. 300 foot [92 meter] coils require two
4" x 8" x 16" [102 x 203 x 406 mm] blocks (19 lbs. [8.6 kg] each)
or 8-10 bricks (4.5 lbs [2.1 kg] each) and every 20 ft [6 meters] of
1-1/4" supply/return piping requires 1 three-hole block. Pond Coils
should be supported off of the bottom by the concrete blocks. The
supply/return trenching should begin at the structure and work
toward the pond. Near the pond the trench should be halted and
back fi lled most of the way. A new trench should be started from
the pond back toward the partially backfi lled fi rst trench to prevent
pond from fl ooding back to the structure.
BUILDING ENTRY
Seal and protect the entry point of all earth coupling entry points
into the building using conduit sleeves hydraulic cement.
Slab on Grade Construction
New Construction: When possible, position the pipe in the
proper location prior to pouring the slab. To prevent wear as the
pipe expands and contracts protect the pipe as shown in Figure
3-10. When the slab is poured prior to installation, create a chase
through the slab for the service lines with 4 inch [102 mm] PVC
street elbows and sleeves.
Retrofi t Construction: Trench as close as possible to the
footing. Bring the loop pipe up along the outside wall of the
footing until it is higher than the slab. Enter the building as close to
the slab as the construction allows. Shield and insulate the pipe to
protect it from damage and the elements as shown in Figure 3-11.
Pier and Beam (Crawl Space)
New and Retrofi t Construction: Bury the pipe beneath the footing
and between piers to the point that it is directly below the point of
entry into the building. Bring the pipe up into the building. Shield and
insulate piping as shown in Figure 3-12 to protect it from damage.
Bryant Geothermal Heat Pump Systems
Figure 3-8: Typical Pond/Lake Loop Confi gurations
Below Grade Entry
New and Retrofi t Construction: Bring the pipe through the wall as
shown in Figure 3-13 For applications in which loop temperature
may fall below freezing, insulate pipes at least 4 feet [1.2 meters]
into the trench to prevent ice forming near the wall.
Pressure Testing
Upon completion of the ground loop piping, hydrostatic pressure
test the loop to assure a leak free system.
Horizontal Systems: Test individual loops as installed. Test entire system
when all loops are assembled before backfi lling and pipe burial.
Vertical U-Bends and Pond Loop Systems: Test Vertical U-bends
and pond loop assemblies prior to installation with a test pressure
of at least 100 psi [689 kPa]. Perform a hydrostatic pressure test on
the entire system when all loops are assembled before backfi lling
and pipe burial.
Water-to-Water System Design Guide
53