Manual 2100-738C
Page
59 of 73
MIS-2750
Hose Bib (A)
Hose Bib (B)
Pump
Isolation Valve
TO WATER COIL
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' 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 38
on page 60):
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
two times the cubic feet size of the dwelling being
heated (includes basement if heated).
B. The average water depth should be a least 4' and
there should be an area where the water depth is
at least 12' to 15' 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' 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 4" field tile (rigid plastic or
corrugated) for water return to the lake or pond.
I. The drain line discharge should be located at least
100' from the dry well location.
J. The drain line should be installed with a slope of
2" per 10' 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, standard
plastic piping can instead be run out into the pond
below the frost and low water level.
FIGURE 37
Cleaning Water Coil
