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and the
simple
aquastat does have
its advantages.
To
help
in
setpoint control,
the
following
equation
can be used.
Reset
Ratio
=
Design Water Temo
-
Indoor
Design Temo
Indoor
Design Temp
-
Outdoor Design Temp
Always
check
local
codes
to
be
sure
hot water
heaters can
be used
as
storage
tanks.
Using
the
electric
elements
in
the-tank
as
a secondary heat source
to
the heat
pump is
app'ealing
in
some
applications, but special
UL
listing
is
required by many
loca1
codes.
Specially listed hot water
heaters are
available.
B.
Hydronic
Side
Circulators
Hydronic circulator
pumps transfer
the
energy supplied
by
the
hydronic
side
of ECONAR's
GeoSource
DualTEK
heat
pumps to
the space
conditioning
heat
exchanger. When selecting
a
circulator,
be sure
to
select
a
quiet operating pump
with
the
ability
to supply
the
required
flow
rate
at the system pressure
drop.
The
circulator
supplying
the heat
pump should
be
placed
in
the
water supply
line into
the
unit
to
provide
the
best
pump
performance.
Individual
zone
circulators should
also be
placed
in
the
supply lines
of
the heat exchangers
they
serve
(Figure
3).
These
pumps
are
often
used
as
the
on/off conuol
mechanism
for
the zone
they
supply.
Zone
valves
are also
commonly
used
for
this
purpose
using
a
common pump (shown
in Figure
1).
cNote:
Select
a
common pump
at the
total
flow
of
all
the zones and the
highest
pressure
drop
ofany
one
parallel
zone.
Small Grundfos pumps (230
VAC)
can be used
as
circulator
pumps.
These
pumps
are impedance
protected
and
do not require additional fusing
if
powered
directly
from
the heat
pump,
since the heat
pump
is
rated to
accept
up to a
1/3
horsepower
circulator.
If
impedance
protected
pumps
are
not
used,
inline
fuses should
be supplied
according to
code.
Pumps must be sized to
provide
the
required
flow
to
a
heat exchanger at
its
corresponding
pressure
drop.
This
pressure
drop
can be
calculated
from
the
total
pressure
drop through
the
piping,
added
to
the pressure
drop
of
the
space
conditioning
heat
exchanger. The
hydronic
side
pressure
drop through
each
particular
heat
pump
is
listed
in
Table
5.
This table
can be used
for
sizing
the
circulating
pump between
the
hydronic
side
of
the heat
pump
and a storage
tank.
Table
5
-
This
table
represents the
minimum
pump sizing required
to supply
the heat
pump's required
hydronic
side
flow
rate
at the pressure
drop
of
the heat
pump
and 30
feet
of
3/4"
type
K
copper tubing or combination
of
elbows
and
pipe.
A
common
problem with circulator
pumps is trapped
air
in
the
system. This
air
accumulates
in
the suction port
of
the
circulator
causing
cavitation in
the
pump,
which
leads
to
premature pump
failure
and
noisy
operation.
The
air
can be
eliminated by completely
purging
the system
or
by
placing
an
air
separator
in
the
plumbing
lines.
The entire
system must be
purged
of
air during
initial
installation
and
pressurized
to
a
10-25
psi
static pressure
to avoid air entering
the
system. This
initial
static
pressure
may fluctuate
but
should always remain
above
zero.
If
a
leak
in
the
system
allows the static
pressure
to
drop,
the
leak must
be
repaired to
assure
proper
system
operation.
Air contilually
entering
the
loop
can cause
corrosion, bacteria,
or
pump cavitation.
The
hydronic
side
circulator
supplying
the heat
pump
should
be
controlled
to
run
only
when
the
compressor
is
also
running.
If
the
circulator
pump is allowed to
circulate cold water through the
system
during
offcycles,
the
refrigerant
in
the heat
pump
will
migrate to
the
hydronic
side heat
exchanger.
This
can
cause
heat
pump
starting problems.
C.
Circulation Fluid
The
fluid
circulating
through
the
hydronic
side
of
the
GeoSource
DualTEK
heat
pump
system
is
the
transfer
medium
for
the
heating being supplied to
the
conditioned
space. Selection
of
this
fluid
is very
important.
Water is
the
most
readily
available
fluid
but
has the
drawback
of
expansion
during
freezing
which
can damage the system.
Extended power
intemrption
to
a
structure
or
the
disabling
of
an
outside
zone (such
as
a
garage
floor)
provides
an
opportunity for
freezing
of
the
circulating
fluid.
Antifreeze
must
be used
whenever
the
possibility
of
freezing exists
from
the
environment. A
propylene
glycol
based
antifreeze
(readily
available through
HVAC
wholesalers)
and
water solution
is
recommended.
Methanol
based
antifreeze is not recommended
for
use
on
any
hydronic
system where heat is
being
added
to
the
system
for
structural heating purposes.
Freeze
protection
for
the
hydronic
side
fluid
down
to
20oF (20Ea
propylene
glycol by
volume
in
water) is recommended
for
most
indoor
applications
(see
Chart
1).
Forry percent
propylene
glycol in
water
(-5oF freeze
protection) is
recommended by radiant tubing manufactures
for
snow
melt applications,
in
order to protect
the
tubing
from
expansion
in
outdoor applications. Using over
4A7o
n
hydronic
side
applications
can
cause
pumping problems
due
to high viscosity.
The water being
added
to
the system
should have
100-
PPM
grain
hardness
or
less.
If
poor water conditions
6
5
t.7
l5-42F (Brute)
7
4.8
26-tt6
9
7.0
26-tt6
11
tr.7
26-116 x
Two
Tank Circulators
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36
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59
67
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