The
existing star scale is not extensive enough to include ground source
heat pumps.
Hypothetically;
if the existing formula and scale were used many Waterfurnace units
would exceed 12 stars on the existing 6 star scale.
Is the
efficiency rating actual or just a manufacturer’s average?
All
heating and cooling systems have a rated efficiency from a U.S.
governmental agency.
Fossil
fuel furnaces have a percentage efficiency rating. Natural gas, LPG,
diesel and fuel oil furnaces have efficiency ratings based on
laboratory conditions.
To
get an accurate installed efficiency rating, factors such as flue gas
heat losses and cycling losses caused by oversizing, blower fan
electrical usage, etc., must be included.
Ground
source heat pumps, as well as all other types of heat pumps, have
efficiencies rated according to their coefficient of performance or
COP.
It’s
a scientific way of determining how much energy the system produces
versus how much it uses. Most ground source heat pump systems have
COPs of 3-5. WaterFurnace’s Envision Series have COP’s of up to
6.8. That means for every one unit of energy used to power the
system, 3-5 units are supplied as heat.
Where
a fossil fuel furnace may be 78-90% efficient, a ground source heat
pump is about 500% efficient. Ground source heat pump manufacturers
and some electric utilities use computers to accurately determine the
operating efficiency of a system for your home or building.
Do ground source systems require much maintenance?
Ground
source systems are practically maintenance free. When installed
properly, the
buried
loop will last for generations. And the other half of the operation –
the unit’s fan,
compressor
and pump – is housed indoors, protected from the harsh weather
conditions.
Usually,
periodic checks and filter changes are the only required maintenance.
What does ground
source mean for the environment?
Ground
source systems work with nature, not against it, by using the solar
energy naturally absorbed by the earth. They burn no fossil fuels and
emit no greenhouse gases, which have been linked to global warming,
acid rain and other environmental hazards.
Ground
Source ™ can provide WaterFurnace earth-loop antifreeze which will
not harm the environment in the unlikely event of a leak. The
majority of the WaterFurnace product line uses R-410A, a
performance-enhancing refrigerant that will not harm the earth’s
ozone layer.
How long is the payback period for a Ground
source system?
To
figure this accurately, you must know how much you’ll save each
year in energy costs
with
a ground source system as well as the price difference between it and
an ordinary heating system and central air conditioner.
As
an example: If you’ll save $2000 per year with a ground source
system and the price difference is $10,000, your payback will be less
than five years. If you install a ground source system in a new home,
the monthly savings in operating costs generally will offset the
additional monthly cost in the mortgage, resulting in an immediate
positive cash flow.
In
a commercial application the capital payback is normally less than
five years.
What is the
Kilowatt size of the furnace that’s being proposed?
Ground
source systems, like furnaces are designed to provide specific
amounts of heat energy per hour. The term “Kilowatt (kw)” refers
to how much heat can be produced by the unit in an hour.
Before
you can determine what size furnace you’ll need, you must
have a heat loss/heat gain calculation done on the structure. From
that, an accurate determination can be made of the size of the system
you’ll need.
Ground
Source™ will arrange this assessment if required.
Most
fossil fuel furnaces are substantially oversized for heating
requirements,
resulting
in increased operating cost and unpleasant temperature swings.
Ground Source
Systems
Are all ground
source heat pump systems alike?
No.
There are different kinds of ground source heat pumps designed for
specific applications.
Many
ground source heat pumps, for example, are intended for use only with
higher temperature ground or ground water applications.
Others
will operate at entering water temperatures as low as -4°C, which
are possible in closed-loop systems.
Very
few brands are designed for winter heating, most ground source heat
pumps will however provide summer air conditioning.
Ground
source heat pumps also can differ in the way they are designed.
Self-contained units combine the blower, compressor, heat exchanger
and coil in a single cabinet.
How does a ground source heat pump work?
Anyone
with a refrigerator or an air conditioner has witnessed the operation
of a heat pump. All of these machines, rather than making heat, take
existing heat and move it from a lower temperature location to a
higher temperature location. Refrigerators and air conditioners are
heat pumps that remove heat from colder interior spaces to warmer
exterior spaces for cooling purposes. Heat pumps also move heat from
a low-temperature source to a high-temperature space for heating.
An
air-source heat pump, for example, extracts heat from outdoor air and
pumps it indoors. 
A
ground source heat pump works the same way, except that its heat
source is the warmth of the earth. The process of elevating
low-temperature heat to over 38ºC
and transferring it indoors involves a cycle of evaporation,
compression, condensation and expansion.
A
refrigerant is used as the heat-transfer medium which circulates
within the heat pump. The cycle starts as the cold, liquid
refrigerant passes through a heat exchanger (evaporator) and absorbs
heat from the low-temperature source (fluid from the ground loop).
The refrigerant evaporates into a gas as heat is absorbed.
The
gaseous refrigerant then passes through a compressor where the
refrigerant is pressurized, raising its temperature to more than
82ºC. The hot gas then circulates through a refrigerant-to-air heat
exchanger where heat is removed and pumped into the building at about
38ºC. When it loses the heat, the refrigerant changes back to a
liquid. The liquid is cooled as it passes through an expansion valve
and begins the process again. To work as an air conditioner, the
system’s flow is reversed.
Does a ground source system heat and cool?
Yes,
ground source heat pumps so versatile is its ability to be a heating
and cooling system in one. With a simple flick of a switch on your
indoor thermostat, you can change from one mode to another. In the
cooling mode, a ground source heat pump takes heat from indoors and
transfers it to the cooler earth through either groundwater or an
underground earth loop system. In the heating mode, the process is
reversed.
Will the minimum
entering water temperature (EWT) affect which ground source heat pump
I buy?
Yes.
If you have an open loop system, your entering water temperatures
(EWTs) may vary widely from 20°C to 4°C.
All
heat pumps can handle temperatures in the moderate-to-warm range e.g
10°C+.
Important
note: A closed loop system, on the other hand, may encounter EWTs
below freezing.
It’s
extremely important to know what EWTs at which your heat pump will
operate most efficiently.
Not
all ground source heat pumps will operate efficiently these
lower temperatures.
Can a ground source
system also heat water?
Yes.
Ground source heat pumps can provide most of your hot water needs on
demand at the same high efficiencies as the heating/cooling cycles.
An
option called a desuperheater can be added to most heat pumps. It
will provide significant savings by heating water before it enters
your hot water tank.
Should I buy a ground source system large enough to heat with no
supplemental heat?
Your
present energy consultant, architect or design engineer should
have/be able to provide a heating and cooling load calculation (heat
loss, heat gain) to guide your equipment selection.
Ground
Source™ will arrange this service if required.
World
wide, ground source heat pumps typically are sized to meet your
cooling requirements.
Note:
In New Zealand the requirement is often to design to heating load.
Depending
on your heating needs, a ground source heat pump will supply 80-100
percent of your design heating load, dependant on design.
Sizing
the heat pump to handle your entire heating needs may result in
slightly lower heating costs, but the savings may not offset the
added cost of the larger heat pump unit and larger loop installation.
This should be taken into account by the system designer and
economically sensible options presented.
An
oversized unit may cause dehumidification problems in the cooling
mode, resulting in a loss of summer comfort.
Do I need to increase the size of my electric
service?
Ground
source heat pumps don’t use large amounts of resistance heat so
your existing service may be adequate. Generally, a 80-amp service
will have enough capacity and smaller amp services may be large
enough in some cases. Ground Source or your electrical contractor can
determine your service needs.
Is a ground source heat pump difficult to
install?
Most
units are straight forward to install, particularly when they replace
another forced-air system. They can be installed in areas unsuitable
for fossil fuel furnaces because there is no combustion, thus no need
to vent exhaust gases. Ductwork must be installed in homes that don’t
have an existing air distribution system. The difficulty of
installing ductwork will vary and should be assessed by a contractor.
Another
popular way to use ground source technology is with in-floor radiant
heating, in which hot water circulating through pipes under the floor
heats the room.
How do I know if the dealer and loop installers
are qualified?
Ground
Source™ staff are trained and qualified with both the International
Ground Source Heat Pump Association (IGSHPA) and WaterFrunace.
Can a Ground source heat pump be added to my
fossil fuel furnace?
Split
systems easily can be added to existing furnaces for those wishing to
have a dual-fuel heating system. Dual-fuel systems use the heat pump
as the main heating source and a fossil fuel furnace as a supplement
in extremely cold weather if additional heat is needed.
I have a pond nearby. Can I put a loop in it?
Yes,
if it’s deep enough and large enough. A minimum of 1.8 meters in
depth at its lowest level during the year is needed for a pond to be
considered.
The
amount of surface area required depends on the heating and cooling
load of the structure.
You
should opt against using water from a spring, pond, lake or river as
a source for your heat pump system unless it’s proven to be free of
excessive particles and organic matter. They can clog a heat pump
system and make it inoperable in a short time.
I have ductwork, or existing under-floor heating. Will it work with
this system?
In
all probability, yes. Your installing contractor should be able to
determine ductwork
requirements
and any minor modifications if needed.
If
your radiant under-floor system is hydronic (water) only minimal
modification is required.
The Loop
Does the underground
pipe system really work?
The
buried pipe, or earth loop, was an important technical advancement in
heat pump
technology.
The idea of burying pipe in the ground to gather heat energy
originated in the
1940s.
New heat pump designs and more durable pipe materials have been
combined to
make
ground source heat pumps the most efficient heating and cooling
systems available.
Do I need separate ground loops for heating and
cooling?
No.
The same loop works for both. To switch heating to cooling, or vice
versa, the flow of
heat
is simply reversed.
What types of loops are available?
There
are two main types: open and closed.
What is an open loop system?
An
open loop system uses groundwater from an ordinary well/bore as a heat
source.
The groundwater is pumped into the heat pump unit where heat
is extracted and the water is disposed of in an environmentally safe
manner, such as reinjection back into the same aquifer or water body.
Because
groundwater is a relatively constant temperature year-round, wells
are an excellent heat source.
How much
groundwater does an open loop system require?
The
water requirement of a specific model is usually expressed in litres
per minute (l.p.m.) and is listed in the unit’s specifications.
Generally, the average system will use 1.6 l.p.m. per kilowatt of
capacity while operating, but the amount of water required depends on
the size of the unit and the manufacturer’s specifications.
Your
contractor should be able to provide this information.
Your
well and pump combination should be large enough to supply the water
needed by the heat pump in addition to your domestic water
requirements. You probably will need to enlarge your pressure tank or
modify your plumbing to supply adequate water to the heat pump.
What do I do with the
discharge water?
There
are a number of ways to dispose of water after it has passed through
the heat pump. 
The
open discharge method is the easiest and least expensive. Open
discharge simplyinvolves
releasing the water into a stream, river, lake, pond, ditch or
drainage tile. Obviously, one of these alternatives must be readily
available and have the capacity to accept the amount of water used by
the heat pump before open discharge is feasible.
A
second means of water discharge is the return well. A return well is
a second well bore that returns the water to the ground aquifer. A
return well must have enough capacity to dispose of the water passed
through the heat pump. A new return well should be installed by a
qualified well driller. Likewise, a professional should test the
capacity of an existing well before it is used as a return.
Are there any laws
that apply to open loop installations?
All
or part of the installation may be subject to local ordinances,
codes, covenants or licensing requirements. Check with local
authorities to determine if any restrictions apply in your area.
Does an open loop
system cause environmental damage?
No.
They are pollution free. The heat pump merely removes or adds heat to
the water. No pollutants
are added.
The only change in the water returned to the environment
is a slight increase
or decrease in temperature.
Can I reclaim heat
from my septic system disposal field?
No.
An earth loop will reach temperatures below freezing during extreme
conditions and
may
freeze your septic system. Such usage is banned in many areas.
What problems
can be caused by poor water quality?
Poor
water quality can cause serious problems in open loop systems. Your
water should be tested for hardness, acidity and iron content before
a heat pump is installed. Your contractor or equipment manufacturer
can tell you what level of water is acceptable. Mineral deposits can
build up inside the heat pump’s heat exchanger. Sometimes a
periodic cleaning with a mild acid solution is all that’s needed to
remove the build-up.
Impurities,
particularly iron, can eventually clog a return well. If your water
has high iron
content,
make sure that the discharge water is not aerated before it’s
injected into a return well.
What
is a closed loop system?
A
closed loop system uses a continuous loop of buried polyethylene
pipe. The pipe is connected to the indoor heat pump to form a sealed,
underground loop through which water
or an environmentally friendly antifreeze-and-water solution is
circulated.
A
closed loop system constantly re-circulates its heat-transferring
solution in pressurized pipe, unlike an open loop system that
consumes water from a well.
Most
closed loops are trenched horizontally in areas adjacent to the
building. However, where adequate land is not available, loops are
vertically bored. Any area near a home or business with appropriate
soil conditions and adequate square meterage will work.
What
if I don’t have room for a horizontal loop? 
Closed
loop systems also can be vertical. Holes are bored up to 100 metres
per 6 kilowatt of heat pump capacity, depending on where you live.
U-shaped loops of pipe are inserted in the holes. The holes are then
backfilled with a sealing solution.
How long will the loop pipe last?
Closed
loop systems should be installed using only high-density polyethylene
pipe. Properly installed, these pipes will last for many decades.
They are inert to chemicals normally found in soil and have good heat
conducting properties. PVC pipe should never be used.
How deep and long
will my trenches be?
Trenches
are normally 1.2 to 1.8 metres deep and up to 400 metres long,
depending on the number of pipes in a trench. One advantage of a
horizontal loop system is being able to lay the trenches according to
the shape of the land.
As
a rule of thumb, 7.5 to 14 meters of trench is required per kilowatt
of system capacity. A well-insulated 180-square-metre home would need
about a 10 kilowatt system with 75 – 140 meters of trench.
The length of the ground loop is determined by the following:
- The peak heating (or cooling) demand of the building - this is the total kilowatts required and determines the correct selection of the WaterFurnace unit
- The thermal conductivity of the ground - the ability of the earth to transfer heat by absorbsion and extraction at the location
- Minimum and maximum sub-surface ground temperature - the earth temperature availiable for extraction or rejection at the location
How are the pipe
sections of the loop joined?
Pipe
sections are joined by thermal fusion. Thermal fusion involves
heating the pipe connections and then fusing them together to form a
joint that’s stronger than the original pipe.
This
technique creates a secure connection to protect from leakage and
contamination.
Can I install an earth loop myself?
It’s
not recommended. Good earth-to-coil contact is very important for
successful loop operation.
Non-professional
installations may result in less-than-optimum system performance.
Will an earth loop affect my lawn or landscape?
No.
Research has proven that loops have no adverse effect on grass,
trees, or shrubs. Most horizontal loop installations use trenches
about 600 milimeters wide. This, of course, will initially leave
temporary bare areas, but they can easily be restored with grass seed
or sod.
Vertical
loops require little space and result in minimal lawn damage.
Learn More
How
can I learn more about Ground source systems?
You
can call us at 0800 47 5667
Email: office@groundsource.co.nz
Or
visit websites such as:
Ground
Source™ is your WaterFurnace dealer in New Zealand.
Electric
utility companies are starting to have information about ground
source systems.
Get
in touch with the experts and start saving on your energy bills right
away!
Glossary
Kw
(Kilowatt): The amount of heat needed to raise the temperature of one
litre of water one degree Celsius . Kw is used to signify the heating
and cooling
capacity
of a system and the heat losses and gains of buildings and homes.
Kw/hr
(kilowatt hour): The number of kilowatts produced in one hour.
Closed
loop system: A heat pump system that uses a loop of buried plastic
pipe as a heat exchanger.
Loops can be horizontal or vertical.
COP
(Coefficient of Performance): The ratio of heating or cooling
provided by a heat pump
(or other refrigeration machine) to the energy consumed by the system
under designated operating conditions. The higher the COP, the more
efficient the system.
Compressor:
The central part of a heat pump system. The compressor increases the
pressure and
temperature of the refrigerant and simultaneously reduces its volume
while causing the
refrigerant to move through the system.
Condenser:
A heat exchanger in which hot, pressurized (gaseous) refrigerant is
condensed by transferring heat to cooler surrounding air, water or
earth.
Cycling
losses: The efficiency of a heating or cooling system is reduced due
to start-upand
shut-down losses. Oversizing a heating or cooling system increases
cycling losses.
Desuperheater:
A device for recovering superheat from the compressor discharge gas
of a
heat pump or central air conditioner for use in heating or preheating
water.
Evaporator:
A heat exchanger in which cold, liquid refrigerant absorbs heat from
the low-temperature
source (fluid from the ground loop).
Fossil
fuel: Combustible fuels formed from the decomposition of organic
matter.
Examples
are natural gas, lpg, wood, fuel oil, diesel, wood pellets, lignite
and coal.
Ground
source heat pump: A heat pump that uses the earth as a heat source
and heat sink.
Heat
exchanger: A device designed to transfer heat between two physically
separated fluids or
mediums of different temperatures.
Heat
Pump: A mechanical device used for heating and cooling which operates
by pumping heat
from a cooler to a warmer location. Heat pumps can extract heat from
air, water, or
the earth. They are classified as either air-source or ground source
units.
Heat
sink: The medium – air, water or earth – which receives heat
rejected from a heat pump.
Heat
source: The medium – air, water or earth – from which heat is
extracted by a heat pump.
Open loop system: A heat pump system that uses ground water well/bore or surface water
from a lake, pond, sea or river as a heat source. The water is returned
to the environment.
Payback:
A method of calculating how long it will take to recover the
difference in costs between
two different heating and cooling systems by using the energy and
operating cost savings from the more efficient system.
Supplemental
heating: A heating system used during extremely cold weather when additional
heat is needed to moderate indoor temperatures. May be in the form of
fossil fuel or electric resistance.
Copyright©Ground
Source Limited 2010
This
information is produced as a guide only. Although every effort has
been made to ensure this information is accurate and up-to-date,
Ground Source and/or its principals or representatives cannot be held
responsible for errors, omissions or inaccuracies that maybe present.
FAQ
