Maritime Geothermal TF-45, Installation And Service Manual

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1-Jul-2017 Page 35 001223MAN-05
TABLE 15 - Required Flow
Heat
Pump
Model
Size
Heat Pump
Flow*
gpm
(L/s)
Domestic
Water Usage
gpm
(L/s)
Total
Flow
gpm
(L/s)
25 8.0 (0.50) 4 (0.25) 12 (0.76)
45 10.0 (0.63) 4 (0.25) 14 (0.88)
55 12.0 (0.76) 4 (0.25) 16 (1.01)
65 14.0 (0.88) 4 (0.25) 18 (1.14)
75 16.0 (1.01) 4 (0.25) 20 (1.26)
80 17.0 (1.07) 4 (0.25) 21 (1.32)
* These are minimum water requirements based on an
entering water temperature of 45° F.
Open Loop Installations
tween the pumping fluid level and the pump intake) would con-
tribute linearly to the flow rate should a larger pump be installed.
In the above example, it was recorded that the flow rate
stabilized at 6 gpm, while the water level dropped from 20 to 29
feet (9 feet). If the intake of a larger pump could be placed so
that a further pumping fluid level drop of 9 feet could be
achieved (total 18 feet), it can be assumed that the flow would
double to 12 gpm. Of course, this should be verified with a sec-
ond test once the larger pump is actually installed.
Well Water Quality
The well water should be tested to be sure it meets mini-
mum standards. Although the threat of poor water quality to
open loop installations is often exaggerated, poor water quality
can lead to rapid heat exchanger failure or frequent servicing.
First, the well should not produce any sand. Sand will
physically erode heat exchanger surfaces, and quickly clog re-
turn (injection) wells. Solids or TDS should be less than 1 ppm
(1 mg/L) if a return well is used.
To avoid scale formation on the inside of the heat pump’s
outdoor loop coil, total hardness should be less than 350 ppm /
350 mg/L. In practice, scaling is very rarely a problem at north-
ern groundwater temperatures of 50°F or less because scale
does not generally form at low well water temperatures (unlike,
for example, in a domestic hot water tank). In more southern
climates, the hardness guideline will be a more important con-
sideration. Should scale form, heat pump performance will
gradually deteriorate, and will require periodic flushing with a
calcium/lime removing solution (see General Maintenance sec-
tion). If the need for periodic flushing is anticipated, the optional
Cupro-Nickel (CuNi) coil and piping should be ordered.
Corrosive (salty) water can cause failure of the inner tube
of the heat exchanger, leading to loss of refrigerant and water
entering the refrigeration circuit, which ruins the heat pump. If
chlorides exceed 20 ppm (20 mg/L), the optional CuNi coil and
piping should be ordered. If chlorides exceed 150 ppm (150
mg/L), or significant Ammonia (>0.5 ppm) or H
2
S (>0.2 ppm) is
present, the use of an open loop system should be reconsid-
ered.
Water Discharge Methods
Water disposal methods vary from area to area. However,
some consideration should be made to prevent the cooled
discharge water from immediately coming in contact with the
supply source. Attempting to return the water to the source well
will eventually cool the water so much that the heat pump will
shut off on its low pressure safety control.
Acceptable methods for disposing of the waste water are
listed below. The waste water is clean; the heat pump has no
effect other than reducing the temperature of the water. Refer
to drawing 000907INF for typical disposal method diagrams.

Second well (return well)

Percolation (Drain, ditch, leaching field)

Pond, river or stream
ENSURE SELECTED METHOD CONFORMS
TO LOCAL REGULATIONS.
A return well should be a minimum of 80 ft. from the supply
well for residential applications. The water returned to the well
It is best to flow the well for as long as possible (e.g. 12
hours) at the flow rate required by the proposed heat pump size.
However, if the test is performed before a larger submersible
pump is installed, it may be assumed that any unused water
level drop during the test (that is, any distance remaining be-
Well Water Temperature
The temperature of the well water should be a minimum of
4 1°F (5°C), and should normally be 45+°F (7°C+). In gen-
eral, groundwater temperatures across the Canadian prairie
provinces and Northern Ontario may be close to the 41°F mini-
mum, while in other parts of southern Canada it will probably be
46-50°F, although local exceptions will exist. In more southern
locations, it will be warmer.
The groundwater temperature should be verified as the first
step in a proposed open loop installation.
Well Water Flow
The water source is normally a drilled water well with sub-
mersible pump that is the same well which supplies domestic
water needs. It must be able to supply the required water flow
as listed under the Total Flow column in TABLE 11 .
For groundwater temperatures of 50°F or greater, these
flows can be reduced by 25% if required.
Rather than being estimated by a well driller, the flow from
a proposed source well should be measured by performing an
extended flow test to be sure it is capable of supplying the re-
quired flow over an extended period of time. This is done by
flowing the well at the highest possible rate, noting the static
water level in the well, and monitoring the pumping fluid level
until stable. Unless the fluid level is very high, fluid level moni-
toring will require a device called a water level sounder. The
flow rate can then be measured either by a cumulative gallon
meter, a flowmeter, or by timing the filling of a bucket of known
size. The test data can be recorded as follows: