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VI.
EARTH LOOP WATER
PIPING
Since water is
the source
of
energy
in
the
wintertime
and
the
energy sink
in
the summertime, good water supply is
possibly
the
most important requirement
of
a
geothermal
heat
pump
system
installation.
There
are
two
cornmon
types
of
water supplies, closed
loop
systems and open
loop
systems.
A.
Closed
Loop Applications
A
closed
loop
system
recirculates
the
same
water/antifreeze solution through
a
closed
system
of
underground high-density polyethylene
pipe.
As
the
solution
passes
through
the
pipe,
it
collects
heat
(in
the
heating mode) that is being transferred
from
the
relatively
warm surrounding
soil
through
the
pipe
and
into
the
relatively cold solution.
The solution is circulated to
the
heat
pump, which
pulls
heat
out
of
the solution,
and
then
back through
the
ground to exffact more
heat
from
the
earth.
The GeoSource
DualTEK
is
designed
to
operate on
either
vertical
or
horizontal
closed loop applications.
Vertical
loops
are
q,pically
installed
with
a
well
drilting
rig
up
to
200
feet deep
or
more. Horizontal
systems
are
tJpically
installed
with
excavating or trenching equipment
approximately six to eight feet
deep,
depending on
geographic
location
and
length
ofpipe
used" Earth loops
must
be sized
properly for
each
particular
geographic
area,
soil
type,
and
individual
capacity requirements.
Contact your
local
installer or
ECONAR's
Customer
Support
for loop
sizing requirements
in your
area.
Since
normal
wintertime
operating entering water
temperatures
(EV/T)
to
the heat
pump
are
from
25oF
to
32oF, the
solution
in
the
earth loop must
include
antifreeze. GTF
and
propylene
glycol
are
common
antifreeze
solutions. GTF
is
methanol-based antifteeze,
which
should
be
mixed
50Vo
withwater
to achieve'freeze
protection
of
10oF. Propylene
glycol
antifreeze solution
should be
nrxed
25Vo
with
water to obtain a
15oF
freeze
protection. DO
NOT
mix
more than25Vo propylene
glycol with
water
in
an
attempt
to
achieve a
lower
than
15oF
freeze
protection,
since
more concentrated mixtures
of
propylene
glycol
become too viscous
at
low
temperatures and
cannot
be
pumped through
the
earth
loop.
Insufficient
amounts
of
antifreeze may result
in
a
freeze
rupture
of
the
unit,
and can cause
unit
shutdown
problems during
cold
weather operation (when
the heat
pump
experiences the
longest run
time)
due
to
loop
temperatures
falling below
tlrre
freeze
protection
of
the
loop
solution.
Flow
rate
requirements
for
closed loops
are
higher than
open
loop
systems because
water temperatures supplied to
the heat
pump
are
generally
lower
(see
Table
6).
Between
2.5 to
3.0
gallons per minute
(GPM)
per
ton
are
required
for
proper operation
of
the heat
pump
and the
earth
coupled
heat exchanger.
TOIFROM
CIOSEDLOOP
\
( -.-..-::_
--ll
IN
OUT
PuopPAK
Pre$sur€/
Topmhnc
(P/T)
P6ls
lt
lt
il
9
Figure
4
-
Closed
Loop Water Plumbing
--l
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