R e s i d e n t i a l S p l i t - 6 0 H z R 2 2 & R 4 1 0 A
R e v. : 5 J u n e , 2 0 0 8
12
W a t e r- S o u r c e H e a t i n g a n d C o o l i n g S y s t e m s
Earth loop temperatures can range between 25 and
110°F [-4 to 43°C]. Flow rates between 2.25 and 3 gpm
per ton [2.41 to 3.23 l/m per kW] of cooling capacity is
recommended in these applications.
Test individual horizontal loop circuits before back
fi
lling.
Test vertical U-bends and pond loop assemblies prior to
installation. Pressures of at least 100 psi [689 kPa] should be
used when testing. Do not exceed the pipe pressure rating.
Test entire system when all loops are assembled.
Flushing the Earth Loop
Once piping is completed between the unit, Flow Controller
and the ground loop (Figures 7 and 8), the loop is ready for
fi
nal purging and charging. A
fl
ush cart with at least a 1.5 hp
[1.1 kW] pump is required to achieve enough
fl
uid velocity
in the loop piping system to purge air and dirt particles. An
antifreeze solution is used in most areas to prevent freezing.
All air and debris must be removed from the earth loop
piping before operation. Flush the loop with a high volume
of water at a minimum velocity of 2 fps (0.6 m/s) in all piping.
The steps below must be followed for proper
fl
ushing.
1. Fill loop with water from a garden hose through the
fl
ush
cart before using the
fl
ush cart pump to insure an even
fi
ll.
2. Once full, the
fl
ushing process can begin. Do not allow
the water level in the
fl
ush cart tank to drop below the
pump inlet line to avoid air being pumped back out to
the earth loop.
3. Try to maintain a
fl
uid level in the tank above the return
tee so that air cannot be continuously mixed back into
the
fl
uid. Surges of 50 psi (345 kPa) can be used to help
purge air pockets by simply shutting off the return valve
going into the
fl
ush cart reservoir. This “dead heads”
the pump to 50 psi (345 kPa). To purge, dead head the
pump until maximum pumping pressure is reached.
Open the return valve and a pressure surge will be sent
through the loop to help purge air pockets from the
piping system.
4. Notice the drop in
fl
uid level in the
fl
ush cart tank when
the return valve is shut off. If air is adequately purged
from the system, the level will drop only 1-2 inches (2.5
- 5 cm) in a 10” (25 cm) diameter PVC
fl
ush tank (about a
half gallon [2.3 liters]), since liquids are incompressible. If
the level drops more than this,
fl
ushing should continue
since air is still being compressed in the loop
fl
uid.
Perform the “dead head” procedure a number of times.
Note: This
fl
uid level drop is your only indication of air in
the loop.
Antifreeze may be added before, during or after the
fl
ushing
procedure. However, depending upon which time is chosen,
antifreeze could be wasted when emptying the
fl
ush cart
tank. See antifreeze section for more details.
Loop static pressure will
fl
uctuate with the seasons.
Pressures will be higher in the winter months than during
the cooling season. This
fl
uctuation is normal and should
be considered when charging the system initially. Run the
unit in either heating or cooling for a number of minutes to
condition the loop to a homogenous temperature. This is
a good time for tool cleanup, piping insulation, etc. Then,
perform
fi
nal
fl
ush and pressurize the loop to a static
pressure of 50-75 psi [345-517 kPa] (winter) or 35-40 psi
[241-276 kPa] (summer). After pressurization, be sure to
loosen the plug at the end of the Grundfos loop pump
motor(s) to allow trapped air to be discharged and to insure
the motor housing has been
fl
ooded. This is not required
for Taco circulators. Insure that the Flow Controller provides
adequate
fl
ow through the unit by checking pressure drop
across the heat exchanger and compare to the pressure
drop tables at the back of the manual.
Antifreeze
In areas where minimum entering loop temperatures drop
below 40°F [5°C] or where piping will be routed through
areas subject to freezing, antifreeze is required. Alcohols
and glycols are commonly used as antifreeze; however your
local sales manager should be consulted for the antifreeze
best suited to your area. Freeze protection should be
maintained to 15°F [9°C] below the lowest expected
entering loop temperature. For example, if 30°F [-1°C] is
the minimum expected entering loop temperature, the
leaving loop temperature would be 25 to 22°F [-4 to -6°C]
and freeze protection should be at 15°F [-10°C]. Calculation
is as follows:
30°F - 15°F = 15°F [-1°C - 9°C = -10°C].
All alcohols should be premixed and pumped from a
reservoir outside of the building when possible or introduced
under the water level to prevent fumes. Calculate the
total volume of
fl
uid in the piping system. Then use the
percentage by volume shown in Table 2 for the amount
of antifreeze needed. Antifreeze concentration should be
checked from a well mixed sample using a hydrometer to
measure speci
fi
c gravity.
Ground-Loop Heat Pump Applications
Low Water Temperature Cutout Setting
CXM or DXM Control
When antifreeze is selected, the FP1 jumper (JW3) should
be clipped to select the low temperature (antifreeze 13°F
[-10.6°C]) set point and avoid nuisance faults (see “Low
Water Temperature Cutout Selection” in this manual). NOTE:
Low water temperature operation requires extended range
equipment.
