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System Flushing and Filling
Once the piping is complete, units require final purging and loop
charging. A flush cart pump of at least 1.5 hp is needed to achieve
adequate flow velocity in the loop to purge air and dirt particles
from the loop. Flush the loop in both directions with a high vol-
ume of water at a high velocity. Follow the steps below to properly
flush the loop:
1.
Verify power is off.
2.
Fill loop with water from hose through flush cart before using
flush cart pump to ensure an even fill. Do not allow the water
level in the flush cart tank to drop below the pump inlet line
to prevent air from filling the line.
3.
Maintain a fluid level in the tank above the return tee to avoid
air entering back into the fluid.
4.
Shutting off the return valve that connects into the flush cart
reservoir will allow 50 psig surges to help purge air pockets.
This maintains the pump at 50 psig.
5.
To purge, keep the pump at 50 psig until maximum pumping
pressure is reached.
6.
Open the return valve to send a pressure surge through the
loop to purge any air pockets in the piping system.
7.
A noticeable drop in fluid level will be seen in the flush cart
tank. This is the only indication of air in the loop.
NOTE: If air is purged from the system while using a 10 in.
15.0
13.0
11.0
9.0
7.0
5.0
3.0
1.0
10
20
30
40
50
72
96
120
Fig. 43 — Water Pressure Drop Curve
PVC flush tank, the level drop will only be 1 to 2 in. since liq-
uids are incompressible. If the level drops more than this,
flushing should continue since air is still being compressed in
the loop. If level is less than 1 to 2 in., reverse the flow.
8.
Repeat this procedure until all air is purged.
9.
Restore power.
Antifreeze may be added before, during or after the flushing pro-
cess. However, depending on when it is added in the process, it
can be wasted. Refer to the System Flow, Antifreeze section on
page 48 for more detail.
Loop static pressure will fluctuate with the seasons. Pressures will
be higher in the winter months than during the warmer months.
This fluctuation is normal and should be considered when
charging the system initially. Run the unit in either heating or cool-
ing for several minutes to condition the loop to a homogenous
temperature.
When complete, perform a final flush and pressurize the loop to a
static pressure of 40 to 50 psig for winter months or 15 to 20 psig
for summer months.
After pressurization, be sure to remove the plug from the end of
the loop pump motor(s) to allow trapped air to be discharged and
to ensure the motor housing has been flooded. Be sure the loop
flow center provides adequate flow through the unit by checking
pressure drop across the heat exchanger. Compare the results to
the data in Fig. 43.
60
70
Flow Rate (GPM)
150/180
210
240/300
47
80
90
360
100
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