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Figure 8D. Valve Position D - Full Flush
Now by switching both valves to this position water will
flow both through the loop and the unit heat exchanger.
Finally the dead head test should be checked again for an
indication of air in the loop. This fluid level drop is
your only indication of air in the loop. Antifreeze may
be added during this part of the flushing procedure
see antifreeze section for details.
Close the flush cart return valve and the after pressurizing
close the flush cart supply valve to pressurize the loop to
a static pressure at least 50 psi. If water pressure is low
General
In areas where minimum entering loop temperatures drop
below 40 F or where piping will be routed through areas
subject to freezing, antifreeze is needed. Alcohols and
glycols are commonly used as antifreezes, however your
local representative should be consulted for the antifreeze
best suited to your area. Freeze protection should be
maintained to 15 F below the lowest expected entering
loop temperature. For example, if 30 F is the minimum
expected entering loop temperature, the leaving loop
temperature would be 25-22 F and freeze protection
should be at 15 F (30 F-15 F=15 F). All alcohol's
should be premixed and pumped from a reservoir outside
of the building when possible or introduced under water
level to prevent fuming. Initially calculate the total
volume of fluid in the piping system using Table 3. Then
use the percentage by volume shown in Table 4 for the
amount of antifreeze. Antifreeze concentration should be
checked from a well mixed sample using a hydrometer to
measure specific gravity.
ANTIFREEZE SELECTION
Figure 8E. Valve position E - Pressurize and Operation
use an air compressor to bump the pressure up through the
P/T port. The loop may be isolated by moving to valve
position E keeping watch on the pressure gauge of the
flush cart for pressure greater than 50 psi. Loop static
pressure will fluctuate with the seasons and pressures will
be higher in the winter months than during the cooling
season. This fluctuation is normal and should be consid-
ered when charging the system initially. Unhook flush cart
from the flow controller. Install counter sink plugs using
sealant compatible with PVC.
Antifreeze Characteristics
Selection of the antifreeze solution for the closed loop
earth coupled systems requires the consideration of many
important factors which have long-term implications on the
performance and life of the equipment. Each area of
concern leads to a different "best choice" of antifreeze.
The fact is that there is no "ideal" antifreeze and any
choice will require compromises in one area or another.
Some of the factors to consider are safety, thermal
performance, corrosiveness, local codes, stability,
convenience, and cost.
Methanol - Methanol or wood alcohol is considered
toxic in any form, good heat transfer, low to mid price,
flammable in concentrations greater than 25%, non-
corrosive, and low viscosity. Methanol has delivered
outstanding performance in earth loops for over 10 years.
Its' only drawbacks are toxicity and flammability.
Although methanol enjoys widespread consumer use as a
windshield washer fluid in even higher concentrations,
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