Table of Contents
Advertisement
for
various levels
of
freeze
protection.
This
table
can
be
used
for sizhg
the
circulating
pump between
the
hydronic
side
of
the heat
pump
and a storage
tank.
Table
4
-
Tank Circulators
*Size
circulators for specific GW240
Note:
See
Table 3, Heat Exchanger
Pressure
Differential
(dP)
Correction Factors
for
Freeze
Protection.
Table 4
represents
the
minimum pump
size
to
supply the
heat
pump's
required
hydronic
side
flow
to
a storage
tank
at
the pressure
drop
of
the heat
pump and 30
feet
of
3/t"
type
K
copper
tubing (or
a
combination
of
approximately
20
feet
with typical
elbows
and
fittings)
(1-114"
pipe
on
87
series
and2" pipeor'240
series).
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
psig static
pressure
to
avoid
air
entering
the
system.
This
static
pressure
may
fluctuate
when going
from
the heating
to cooling
modes
but
should
always
remain
above zero.
If
a
leak
in
the
system
causes
the static
pressure
to
drop, the leak must be repaired
to
assure
proper
system
operation.
The hydronic side circulator
supplying
the
heat
pump
should
be
controlled
to run only
when
the
compressor
runs.
If
the pump
is
allowed
to
circulate
cold
water
through the
system
during
off
cycles,
the
refrigerant
il
the
heat
pump
will
migrate
to
the
hydronic
side
heat
exchanger.
This
can
cause heat
pump starting
problems
(especially
when
this
refrigerant migrates
into
the
condenser).
C.
Circulation Fluid
The
fluid
circulating
through
the hydronic side
of
the
geothermal heat
pump
system
is
the transfer
medium
for
the heating and
cooling 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.
System
operation
in
the cooling
mode,
extended power
htemrption
to
a structure,
or disabling
of
an
outside
zone
(such as
a
garuge
floor)
provides
the opportunity for
freezing
the
circulatiag
fluid.
VCAUTION
-
the
hydronic
side
of
rhe system
must
be
freeze protected
to
reduce
the
risk
of
a freeze
rupture
of
the unit.
A
propylene
glycol
based antifreeze (readily
available through
HVAC
wholesalers) and
water
solution
is
recommended.
A
non-flammable
arttrfreeze
solution
is
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
lSoF (207o
propylene
glycol by volume
in
water)
is
recommended
for
most indoor
applications. Forfy
percent propylene
glycol
in
water
(-5oF
freeze protection)
is
recommended
by
radiant tube
manufactures
for
snow
melt
applications
to protect
the
tubing
from
expansion
in
outdoor applications.
Using over
40Vo
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.
Ifpoor
water conditions
exist
on the site, softened water is recommended,
or
acceptable
water should be brought
in.
Bacteria
or
algae
grouth in
the
water
is
a
possibility
at
the
temperatures produced
in
the
heating
system
and can
cause
buildup
on
hydronic
side heat
exchanger surfaces,
reducing the
efficiency
of
the
system
or
causing the
heat
pump to
run
at
higher
head
pressures
and possibly
lock out.
A
gallon
of
bleach or
boiler
system
conditioner
can
reduce
the possibility
of
growth
and can clean
up other components
in
the system.
D. Expansion Tanks
Expansion
talks
must be
used
in
the
hydronic
side
of
the
water-to-water
system
to
absorb
the
change
in
pressure
of
the closed system due
to
the
change
irr temperature when
heat
is
supplied
to
the system. Diaphragm-type expansion
tanks should
be
used.
Use EPDM
diaphragm
tanks
because
they
are
compatible
with
glycol-based antifreeze
fluids
(butyl rubber
diaphragms
will
slowly
dissolve
with
glycol-based antifreezes).
Expansion tanks
from
I
to
l0
gallons are
generally
used
with
heat pump
systems
in
residential
and
light
commercial applications. Expansion
tanks should
be
installed
in
the
system near
the suction
of
the circulator
pump
to
maintain
positive
pressure
at
the
circulator
pump
and
reduce the highest
working
pressure
of
the system.
A
pressure gauge near the
inlet
ofthe
expansion tank gives
a
good
indication of
how
the system
is operating.
Pressure
relief
valves
are
required
on
hydronic
applications.
A
30
psig
relief is
adequate
if
the system is
operated
at
12
A
15 psig
pressure.
If
a
water
heater
is
used
for
a
storage
tank, the
150
psig
pressure
relief
may
be acceptable
(check local
codes).
E.
Application Diagrams
Figures
1
through
5
show the
components
of
a
hydronic
heat
pump
system discussed
above
used
in
some
cofitmon
applications.
These
figures by no
means represent
all
the
9
3V
5
1.7
15-42F (Brute)
47
1
4.8
26-tt6
9
7.0
26-116
77
12
14.1
26-i
16
x
Two
87
t4
3.6
26-rL6
240
40
2.1
*
Series
FIow
(gpm)
dP
(nsip)
Grundfos
Circulator
- Quick Links:
- Econar
- Unit Sizing
Hide quick links:
Advertisement
Table of Contents
