15
R e s i d e n t i a l H & V - 6 0 H z H F C - 4 1 0 A
R e v : O c t o b e r 5 , 2 0 2 1
c l i m a t e m a s t e r.c o m
Ground-Loop Heat Pump Applications
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 flushing.
1. Fill loop with water from a garden hose through the flush
cart before using the flush cart pump to insure an even fill.
2. Once full, the flushing process can begin. Do not allow
the water level in the flush 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 fluid level in the tank above the return
tee so that air cannot be continuously mixed back into
the fluid. Surges of 50 psi (345 kPa) can be used to help
purge air pockets by simply shutting off the return valve
going into the flush 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 fluid level in the flush 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 flush tank (about a half gallon
[2.3 liters]), since liquids are incompressible. If the level
drops more than this, flushing should continue since air is
still being compressed in the loop fluid. Perform the “dead
head” procedure a number of times.
Note: This fluid level
drop is your only indication of air in the loop.
Antifreeze may be added before, during or after the flushing
procedure. However, depending upon which time is chosen,
antifreeze could be wasted when emptying the flush cart
tank. See antifreeze section for more details.
Loop static pressure will fluctuate with the seasons.
Pressures will be higher in the winter months than during
the cooling season. This fluctuation 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 final
flush 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
flooded. This is not required for Taco circulators. Insure
that the Flow Controller provides adequate flow 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. Low temperature 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 low temperature 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 fluid 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 specific
gravity.
Table 1: Approximate Fluid Volume (gal.) per 100' of Pipe
Fluid Volume (gal [liters] per 100’ [30 meters) Pipe)
Pipe
Size
Volume (gal) [liters]
Copper
1”
4.1 [15.3]
1.25”
6.4 [23.8]
2.5”
9.2 [34.3]
Rubber Hose
1”
3.9 [14.6]
Polyethylene
3/4” IPS SDR11
2.8 [10.4]
1” iPS SDR11
4.5 [16.7]
1.25” IPS SDR11
8.0 [29.8]
1.5” IPS SDR11
10.9 [40.7]
2” IPS SDR11
18.0 [67.0]
1.25” IPS SCH40
8.3 [30.9]
1.5” IPS SCH40
10.9 [40.7]
2” IPS SCH40
17.0 [63.4]
Unit Heat Ex-
changer
Typical
1.0 [3.8]
Flush Cart Tank
10” Dia x 3ft tall
[254mm x 91.4cm tall]
10 [37.9]
Low Water Temperature Cutout Setting
- CXM Control
When antifreeze is selected, the FP1 jumper (JW3) should
be clipped to select the low temperature (antifreeze 10°F
[-12.2°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.
