FIGURE 24
CLEANING WATER COIL
Hose Bib (B)
Isolation Valve
Hose Bib (A)
TO WATER COIL
Pump
FROM WATER COIL
LAKE AND POND INSTALLATIONS
Lakes and ponds can provide a low cost source of water for heating and cooling with a ground water heat pump. Direct usage of the water without some filtration is not recommended as algae and turbid water can foul the water to freon heat exchanger. Instead, there have been very good results using a dry well dug next to the water line or edge. Normal procedure in installing a dry well is to backhoe a 15 to 20 foot hole adjacent to the body of water (set backhoe as close to the water’s edge as possible). Once excavated, a perforated plastic casing should be installed with gravel backfill placed around the casing. The gravel bed should provide adequate filtration of the water to allow good performance of the ground water heat pump.
The following is a list of recommendations to follow when installing this type of system (Refer to Figure 25):
A. A lake or pond should be at least 1 acre (40,000 a square feet) in surface area for each 50,000 BTUs of ground water heat pump capacity or have 2 times the cubic feet size of the dwelling that you are trying to heat (includes basement if heated).
B.The average water depth should be a least 4 feet and there should be an area where the water depth is at least 12 to 15 feet deep.
C.If possible, use a submersible pump suspended in the dry well casing. Jet pumps and other types of suction pumps normally consume more electrical energy than similarly sized submersible pumps. Pipe the unit the same as a water well system.
D. Size the pump to provide necessary GPM for the ground water heat pump. A 12 GPM or greater water flow rate is required on all modes when used on this type system.
E.A pressure tank should be installed in dwelling to be heated adjacent to the ground water heat pump. A pressure switch should be installed at the tank for pump control.
F.All plumbing should be carefully sized to compensate for friction losses, etc., particularly if the pond or lake is over 200 feet from the dwelling to be heated or cooled.
G.Keep all water lines below low water level and below the frost line.
H.Most installers use
I.The drain line discharge should be located at least 100 feet from the dry well location.
J.The drain line should be installed with a slope of 2 inches per 10 feet of run to provide complete drainage of the line when the ground water heat pump is not operating. This gradient should also help prevent freezing of the discharge where the pipe terminates above the frost line.
K.Locate the discharge high enough above high water level so the water will not back up and freeze inside the drain pipe.
L.Where the local conditions prevent the use of a gravity drainage system to a lake or pond, you can instead run standard plastic piping out into the pond below the frost and low water level.
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