Comfort-Aire HTS Series Split System,Two Stage, 2-5 Tons - Manual (Page 10)

10
Installation, Operation & Maintenance HTS SERIES SPLIT SYSTEM Heat Controller, LLC
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 backfi 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 (Figure 4), 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 specifi c gravity.
Low Water Temperature Cutout Setting - DXM2 Control
When antifreeze is selected, the LT1 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.
Ground-Loop Heat Pump Applications