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Once piping is completed between the unit, flow
controller and the ground loop, final purging and
charging of the loop is needed.
A flush cart (at least a 1.5 hp pump) is needed to achieve
adequate flow velocity in the loop to purge air and dirt
particles from the loop itself. Antifreeze solution is used
in most areas to prevent freezing. All air and debris must
be removed from the earth loop piping system before
operation, Flush the loop with a high volume of water at
a high velocity (2 fps in all piping), both directions using
a filter in the loop return line, of the flush cart to eliminate
debris from the loop system. The steps below must be
followed for proper flushing.
Figure 8A. Valve Position A - Loop Fill
Fill loop with water from a garden hose through flush
cart before using flush cart pump to ensure an even fill
and increase flushing speed. When water consistently
returns back to the flush reservoir switch to valve
position B.
Figure 8B. Valve position B - Unit Fill
FLUSHING THE EARTH LOOP
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This position should be switched while filling to fill the
unit heat exchanger and hose kit. This should be maintained
until water consistently is returned into the flush reservoir.
Figure 8C. Valve Position C- Loop Flush
Switch to valve position C. The supply water may be shut
off and the flush cart turned on to begin flushing. Once
the flush reservoir is full, do not allow the water level in
the flush cart tank to drop below the pump inlet line or air
can be pumped back out to the earth loop. Try to maintain
a fluid level in the tank above the return tee so that air can
not be continuously mixed back into the fluid. 50 psi
surges 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. To dead
head the pump until maximum pumping pressure is
reached, open the valve back up and a pressure surge will
be sent through the loop to help purge air pockets from
the piping system. Notice the drop in fluid level in the
flush cart tank. If all air is purged from the system, the
level will drop only 1-2 inches in a 10" diameter PVC
flush tank (about a half gallon) since liquids are
incompressible. If the level drops more than this, flushing
should continue since air is still being compressed in the
loop fluid. Do this a number of times. When the fluid
level is dropping less than 1-2" in a 10" diameter tank the
flow can be reversed.
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