The Citizen, 1991-05-15, Page 20PAGE 20. THE CITIZEN, WEDNESDAY, MAY 15,1991.
M'OfWE LJM’lZtX 1991
Heat pumps cool,heat economically
MAITLAND MANOR
NURSERY
BLUEVALE 335-3240
Bare Root Specials
15" + Colorado Spruce $5.
15" + Norway Spruce $4.
18 - 24” Scotch Pine $4.
15” Scotch Pine $2.
tractor when add-on heat pump sys-
Basic Heat Pump Cycle
High pressure.
High Temperature Vapor
High Pressure.
High Temperature Liquid
◄i
CONDENSOR
COMPRESSOR
Lou pressure.
Lou Temperature Vapor
EVAPORATOR
Lou Pressure.
Low Temperature Liquid
EXPANSION
VALVE
If you are considering adding
central air conditioning, replacing
your existing central air conditioner
or furnace, building a new home, or
just want to save energy and
money, think first about a heat
pump. A heat pump is quite simply
the most energy efficient heating
system on the market today.
The fact that a heat pump pro
vides both heating and air condi
tioning for your home, makes the
heat pump an ideal year-round
space conditioning system. This is
accomplished by taking advantage
of the scientific principle that heat
flows from hot areas to cooler ones.
The heat pump is changed from an
air conditioner to a heating system
through a reversing valve that
changes the refrigerant flow. In the
heating mode, the outdoor coil con
tains refrigerant which is colder
than the outdoor air. A fan blows
outdoor air across the coil where
heat is absorbed by the refrigerant.
When the refrigerant temperature
has increased, it is pumped to the
indoor coil. The heal is then
released into your home heating
duct system by a fan blowing
across the ir.door coil.
In the summer, the heat pump
functions like a regular air condi
tioning system keeping your home
cool and dry.
Unlike other healing systems, the
heat pump transfers existing heal
from the outdoor air to the inside of
your house, rather than creating
heat from an energy source like
gas, oil or electricity. Because heat
pumps use existing heat, they can
produce anywhere from 1.7 to 2.0
units of heat energy for each unit of
electric energy consumed. Il does
this by relying on the fact that there
is heat available in the outdoor air
until the temperature reaches -273
degrees centigrade. Even at -20
degrees centigrade, the outside air
contains over 80 per cent of the
heat that is available at 38 degrees
centigrade.
There are two basic types of heat
pumps, the ground-source heat
pump, and air to air heat pumps.
The earth temperature under your
house changes very little all year
long. In the winter the soil is
warmer than the outside air. The
ground-source heat pump extracts
this free energy and transfers it to
your house in its heating mode. In
the summer, the soil is cooler than
the outside air and the cycle is
reversed. The ground-source heat
pump extracts heat from your
house and transfers it to the soil in
the cooling mode. The transfer
from cooling to heating is done by
your room thermostat. All GSHP s
have two parts. A heat pump unit
INSIDE the house, and a circuit of
underground piping outside the
house.
The air to air heat pump operates
on a similar principle, but the heat
exchanging is done into the air. It is
available in two versions: An add
on heat pump which operates in
sequence with your existing gas,
oil, or electric furnace and its popu
lar alternative, the complete con
ventional system. Heat pumps
operate in winter most efficiently at
temperatures above -1 degrees C.
Gas and oil furnaces in particular
operate most efficiently at low tem
peratures, since they run longer and
more frequently than at high tem
peratures. When temperatures drop
below freezing, the heat pump cuts
off and the gas, oil or electric fur
nace takes over. The add-on heat
pump in the summer operates like a
conventional air conditioner. So
you have year-round comfort and
economy^
As the outdoor temperature
decreases, there is less heat avail
able in he air, and the heating
capacity of the heal pump decreas
es. Since the amount of heat
required for your home increases as
the outdoor temperature drops,
there is a temperature below which
the total heating requirement for
your home cannot be met by the
heat pump alone. This temperature
is called the "balance point."
With the add-on heal pump, the
balance is manually set by the con-
terns are installed. Once set, the
system will automatically switch
from the heal pump to the furnace
as the outdoor temperature drops
below the balance point. This com
bination of systems allows opti
mum performance from both the
heat pump and the backup system.
In the case of the conventional
heat pump, when the outdoor tem
perature drops below the balance
point, electric resistance heaters are
switched on automatically to sup
plement the heat pump and keep
you comfortable. Even with the
supplemental resistance heat, a
properly designed and installed
heat pump system should have an
operating cost less than your cur
rent system. In fact, a heat pump
will have a total owning and oper
ating cost which is competitive
with any heating system.
Heat pumps, like all heating sys
tems, work more efficiently in
houses that are well insulated and
weatherized. Therefore, when
adding a heat pump system, it is a
good time to make sure your home
has adequate insulation, storm win
dows, caulking and weatherstrip
ping.
In either system, your ductwork
may need some changes to handle
the airflow required for a heat
pump. Your heating contractor will
be able to tell you if your existing
ductwork is adequate. For more
information call 1-800-363-3801.
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