The ground heat exchanger consists of loops of plastic pipe arranged either vertically or horizontally through which an anti-freeze solution is pumped. The ground heat exchanger picks up heat from the ground and transfers it to the heat pump. The loops of piping must be long enough for adequate heat transfer and must be properly spaced to ensure the best performance.

Pipes that run from the home to the ground heat exchanger are called runouts (or headers). The right size of pipe must be used and supply and return runouts must be separated to prevent heat transfer between the two.

For the ground heat exchanger fluid to effectively transfer earth energy to the heat pumps it must be circulated at an adequate rate. Too low a rate of flow will mean insufficient heat transfer whereas too high a rate of flow wastes pump energy. A circulation pump moves the fluid through the piping.

The heat pump extracts heat from the ground heat exchanger fluid and increases its temperature to a level that is useful for heating. This process is reversed by the heat pump when the home is being cooled. Figure 1.2 shows the working of a heat pump diagrammatically. For EESs, the heat pumps are generally water-to-air units (shown) or occasionally water-to-water units depending on the distribution system.

The distribution system is the means by which the heat from the EES is supplied to the home. The distribution system can be either air or hydronic (water). Air systems use ducts to channel air to each room as with a forced air furnace system. The system also includes a fan, a filter and return air ductwork. A fresh air supply to bring in outdoor air should also be part of the system.

Hot water (hydronic) systems are usually of the baseboard radiator type, but they can also be vertical radiator or underfloor systems. They consist of supply and return piping to the radiators or underfloor pipes, with a circulation pump and expansion tank. Hydronic systems can be used for heating only, because condensation problems will result when cooling. Therefore a separate forced air distribution system would be required for cooling.

Different Types of Earth Energy Systems
EESs can be separated into three distinct types, depending on the energy source. These three are: ground-source, groundwater, and lake loop systems.

Ground-source Systems
Ground-source systems take the energy out of the ground but do not make use of the groundwater itself as a circulating fluid. Energy is extracted by means of a ground heat exchanger, which can be of a horizontal or vertical design.

A horizontal heat exchanger consists of pipes buried in the ground at a depth of about 1 to 2 m, forming a series of loops. The fluid circulating in these pipes absorbs heat energy from the ground. The pipes are usually of high-density polyethylene (HDPE) and all joints are fused to avoid leakages. Figure 1.3 depicts a typical horizontal ground heat exchanger, showing the supply and return runouts and piping loops. The piping is placed in trenches which are usually excavated by a backhoe or trencher. The loop piping can also be arranged in a spiral geometry, increasing the pipe area per length of trench. This configuration is sometimes called a "slinky" ground heat exchanger due to its similar shape to the popular toy.

Groundwater Systems
You can use groundwater as a heat source and sink. This is a good choice if groundwater is plentiful at your site and especially if there are already one or more unused wells present. Local regulation should be checked however, to ensure that a groundwater system is allowable in your area. Groundwater systems consist of a supply well and a return well, as shown in Figure 1.5. Groundwater is extracted from the supply well by a pump (usually a submersible pump is used) and piped to the heat pump. The groundwater is then returned to the ground through the return well rather than discarded to the surface or sewer to preserve the quantity and quality of groundwater in the area. Your contractor should be aware of the location of surrounding wells so that the new wells can be positioned so as not to adversely affect the capacity of the existing wells. The supply well should not be positioned where it will receive groundwater from the return well. Otherwise, groundwater from the return well will mix with the supply well, reducing the efficiency of the system. Therefore your contractor should determine the direction of ground water flow in the vicinity of the new wells, and how the new wells will affect this flow.

Lake Loop Systems
Lake loop systems (also called surface-water systems) consist of coils of pipe, called spools, which are immersed in the lake to absorb and reject heat to the lake (see Figure 1.6). These piping loops can also be spread out to increase surface area. The size of the lake must be adequate for the EES to run efficiently. As a general rule, a lake must have 750 to 1000 m2 of surface area for a typically sized house, where a minimum depth of 2 m is maintained within this surface region. As with other earth energy systems, installing a lake loop system must be approved by the local authorities, since such systems may not be permitted in some waterways. Local requirements often call for protection of headers and the need to trench the bed of the waterway to protect against ice, erosion and recreational activity.

Benefits of Earth Energy Systems

Environmental
There are significant environmental benefits associated with EESs. These benefits are linked to the high level of thermal efficiency of these systems. Instead of directly converting electricity into heat energy, EESs use electrical power to raise the temperature of the renewable energy from the earth to a level useful for heating a home. They transfer a greater amount of energy than they consume in transferring, giving a much higher level of performance than other heating systems. Typically an EES will deliver 3 to 4 times the input electrical energy required to operate the system. This leads to lower overall carbon dioxide emissions than a gas furnace, for instance, even if the electricity used to run the earth energy system were generated by a gas-fired power station. In fact, the global warming impact is 15% to 77% lower than competing heating and cooling technologies.

Year-round Comfort
EESs give year-round comfort because they both air condition and heat. The systems can switch automatically between heating and cooling at any time. This results in increased comfort in the spring and fall, when the outdoor temperature can alternate above and below comfort conditions from day to day. Also, if more than one heat pump is installed, each supplying separate zones in the home, one can be heating and the other cooling at the same time.

Low Operating Cost
The operating cost of an EES can often be considerably lower than that of other heating systems because of the high level of efficiency and the additional savings on fuel costs. However, the actual savings will depend on the relative costs of other energy sources in your area. Figure 1.7 compares groundwater and ground heat exchanger (closed loop) earth energy systems with electric furnace, oil furnace, gas furnace, and air-source heat pumps for three locations across Canada. Using the estimates given in the figure, along with a quote from a contractor on the cost of a conventional system (with air-conditioning), you can calculate the length of time it will take you to pay off the incremental cost of your EES from the savings you obtain. Remember to include any savings you may have in maintenance contract cost as well (see section below).

Maintenance and Service Life
EESs require little maintenance on your part, except for regular filter changes. Other maintenance (cleaning ductwork, fan, and heat exchangers, etc.) should be part of a regular maintenance contract. Annual maintenance cost for EES systems should not exceed that of an oil or gas furnace with air-conditioning.

The expected life of the heat pump in an EES is also longer than all other climate control options. Because the source temperature is more consistent, and because there are no sudden temperature changes from a defrost cycle, the thermal stress on the heat pump compressor is lower. Therefore the expected life is longer (by about 4 years on average). This gives a heat pump life of about 19 years. The ground heat exchanger with HDPE piping will last from 25 to 75 years.

Integration of Domestic Hot Water Heating
Savings in domestic hot water (DHW) heating cost can also be achieved with an EES. Many EESs come with a device called a desuperheater. A desuperheater is a heat exchanger within the heat pump that preheats DHW before it enters the hot water heater. Some EESs are designed to heat DHW on demand. Features such as these can reduce your DHW bill by 15 to 40%.

Non-Intrusive
Unlike air-source heat pumps and central air-conditioning systems, EESs do not have an outside unit. This gives you more flexibility in the use of outdoor space and landscaping and improves the appearance of your home. Because EESs use water source heat pumps which are located indoors, outdoor noise levels are non-existent.

Other Benefits
Because all the mechanical components of an EES are inside, they are not prone to damage, vandalism, or the elements. EESs can be applied to almost any residential configuration and location, with the type of system dependent on land or water availability, soil conditions, local regulations, etc.

Water and Ground Resources

Groundwater Quantity and Quality
For groundwater systems, the quantity of groundwater is critical. Typically, 0.05 to 0.08 L/s of groundwater is required per kilowatt of heat pump capacity. Therefore the well yield must provide this capacity in addition to domestic water needs (if a common use well). If the domestic water well system is used to supply the heat pump you may need to enlarge the pressure tank and the associated piping.

The quality of the groundwater is also important. You should have the water tested for acidity, hardness, and iron content since this can affect equipment selection. Your equipment manufacturer or contractor can advise on these requirements.

Ground Heat Exchanger Requirements
For ground heat exchanger systems, the primary concern is the availability of land, since a horizontal ground heat exchanger is cheaper to install than a vertical one. Generally, a horizontal heat exchanger requires 35 to 50 m of piping per kilowatt of heat pump capacity. Therefore, a 185 m2 home, for example, with a 10.5 kW heat pump, would require 370 to 525 m of pipe. The amount of yard space you need for this can be reduced by employing multiple pipes per trench, or by using the "slinky" type of heat exchanger configuration. A test trench should be dug initially to determine soil conditions. If there is insufficient space for a horizontal ground heat exchanger, or if the disruption to the landscaping is judged too excessive, a vertical heat exchanger should be considered. For this, proper knowledge of the sub-strata conditions is required, and the contractor should drill a test borehole to determine this. This test borehole can then become one of the actual test heat exchanger boreholes. The sub-strata information will be useful to determine the heat transfer conditions, practical boring depth, and number of boreholes required. Thus an accurate cost estimate for the system can be obtained. Figure 1.8, while exaggerated, shows a variety of sub-strata conditions.

Site Restrictions
It is important to check local survey information for accurate knowledge of land boundaries and easements as well as required setbacks from property lines. Local utilities and others should also be contacted to verify the location of electrical cables, gas lines, cable TV, water mains, and other buried services. Note a ground heat exchanger must not be installed in a septic bed or close to it.

EARTH ENERGY SYSTEMS FOR A NEW HOME

Home Design Considerations

Energy Efficient Features
If you are considering an EES, now is a good time for you to also consider improvements to the thermal efficiency of your new home and/or the addition of energy efficient features. This will have a double benefit as it will also decrease the size of the EES you require and thus reduce its cost. There are many energy saving options you can choose.

Increasing the insulation level of the roof and walls will reduce the heating and cooling load of the home and will also add to comfort levels by increasing the winter time perimeter wall temperatures, reducing drafts and radiant heat losses.

Thermally efficient windows can add to the energy efficiency and interior comfort of your home. Windows should be chosen carefully since there is often a decrease in solar heat gain with increased number of panes or low emissivity (low-e) coatings. In heating dominated climates, this may dictate a different choice of windows for the south facing side of the home, than for the other sides.

If a separate ventilation system is planned, specifying a heat recovery ventilator (HRV) to transfer the heat from the exhaust air to the fresh ventilation air entering the home, helps to reduce the load imposed on the earth energy system.

For sources of information on how you can make your home more energy efficient see the Further Reading section at the end of this Guide.

Planned Location of In-ground Equipment and Services

It is important to have adequate clearance between the EES and other planned or existing in-ground items such as swimming pools, wells and septic systems. This should include space for the trencher, backhoe, or driller. The work should be done in such a way as to minimize the disturbance to existing pavements, walkways, easements and other rights of access. Piping locations should be noted on a site plan so as to reduce the risk of damage during possible future excavating.

The ground heat exchanger piping should not cross other underground services such as gas lines, water mains, sewers, buried telephone and electrical lines, unless due consideration is given to protecting these from damage during installation or from subsequent freezing. All installation should be done in accordance with the latest CSA 445 standard Design and Installation of Earth Energy Heat Pump Systems for Residential and Other Small Buildings.

The pipes from the ground heat exchanger should enter the house at a location that minimizes the length of the runouts, and the heat pump and its equipment should be located as close as possible to this point of entry. Horizontal pipes which pass under walkways, driveways and decks should have insulation placed above them.

System Design for a New Home

Heat Pump Selection
The selection of the type of heat pump will depend on your distribution system. Forced air systems will require a water-to-air heat pump whereas hydronic (water heating) systems will require a water-to-water heat pump. The contractor must make sure that the capacity of the unit is correct for the space heating and water heating requirements of your home. If the capacity is too small, it will mean poor performance with an inability to meet these requirements. If capacity is too large, money will be wasted due to the higher cost of a larger unit, and the unit will also dehumidify poorly when cooling.

The energy efficiency rating of the unit is also important. This is usually expressed as the coefficient performance (COP) and energy efficiency ratio (EER). The COP is a measure of the heating efficiency of the heat pump and the EER is a measure of its cooling efficiency. The higher the COP and the EER, the more efficient the unit.

Domestic Hot Water Heating
The heat pump can also be used to heat domestic hot water (DHW). There are two ways of doing this: DHW pre-heating with a desuperheater or full DHW heating with an integrated "on demand" system.

A desuperheater is a heat exchanger that transfers heat from the heat pump to the DHW. It does not supply all the necessary heat to the DHW, but serves only to preheat it. Desuperheaters add to the initial costs, but save enough in domestic hot water heating to give a simple payback period of about 5 years (depending on the amount of water used and the number of people in your household).

Integrated "on demand" systems provide more of the heat required for the DHW by using a separate heat exchanger that allows heat from the heat pump to be transferred to the DHW tank when needed. Replacing the gas or electric resistance heating elements with an integrated system is more costly but the savings in hot water heating costs are greater, giving a simple payback period of about 4 years.

Hybrid Designs
In the Canadian climate, the heating demand for a home often exceeds the cooling requirement by a considerable amount. Therefore, if the ground heat exchanger, lake loop, or well for an EES were sized to meet the full heating capacity of the home, it would be considerably larger than necessary for cooling alone. Also, this heating capacity is required only for limited periods during the winter. On most days the smaller size of ground heat exchanger required for cooling will be sufficient for heating as well. With hybrid systems, the ground heat exchanger, well, or lake loop is sized for the maximum cooling demand, and an auxiliary heat source such as an electric resistance heating element is added to the system to meet the peak heating loads. The auxiliary heat source can also be oil, propane or wood.

Hybrid systems can save on capital cost, due to a shorter heat exchanger loop. Heating costs will be slightly higher, but the capital cost savings should more than offset the increased operating costs. As a side benefit, a hybrid system may give better air conditioning comfort in the summer, since the smaller heat pump will run more continuously, giving better humidity control in the home.
Whether the system is a hybrid or not, proper ground heat exchanger sizing is important, due to the cost of a ground heat exchanger and its impact on system performance. A vertical ground heat exchanger is particularly cost-intensive because drilling is more expensive than trenching. There are also uncertainties regarding the difficulties that may be encountered when drilling. The contractor, therefore, must do an accurate ground heat exchanger size calculation to ensure that money is not wasted through over-sizing. There are several computer programs available for ground heat exchanger sizing.

Distribution Systems
A distribution system transfers the heating or cooling of the heat pump throughout the home.

Types of Distribution Systems
There are two basic types of distribution systems: forced air and hydronic (water heating). A forced air system is composed of a fan which directs the air through ductwork to floor-mounted registers in the different rooms (see Figure 2.1). Return air is taken through grilles and directed back to the fan by the return air ducts. Before entering the fan, the air is filtered and then heated or cooled by the heat pump. This system is similar to the familiar forced air furnace system, except that the furnace burner and heat exchanger is replaced by the heat pump, and the fan and ductwork is sized for a higher air quantity (typically 20-30% more). Condensation on the heat pump coils when cooling is trapped with a drain pan and piped to the closest drain or sump. This enables forced air systems to be suitable for both heating and cooling.

Figure 2.1: Forced Air Distribution System
A hydronic system incorporates a pump, piping system, radiators or underfloor coils, an expansion tank, and a heat exchanger. Figure 2.2 shows a baseboard radiator hydronic system. The heat pump heats the water in the heat exchanger and it is circulated by the pump to the radiators or in-floor pipes in the various rooms. Because the heat exchanging surfaces, whether radiators or floor, are large areas distributed throughout the home, their cool surfaces will cause condensation problems that are difficult to control. Therefore hydronic distribution systems are generally only practical for heating and a separate forced air system will be required for cooling.

Figure 2.2: Baseboard Hydronic System

Hydronic heating does, however, as it has several advantages over a forced air system. It gives a more even heat throughout the home, with less variation in temperature with time, reducing drafts and uncomfortable temperature variations. This is particularly true of in-floor heating (Figure 2.3) which supplies heat at a lower temperature because it has a larger area than baseboards. Hydronic heating also reduces the amount of airborne dust in your home since there is no fan blowing the air around. This may be a significant benefit for those who suffer from an allergy to house hold dust. (This advantage will hold regardless of how good the filtration system of a forced air system, since most of the dust circulating in the home does not go through the hot air system itself). In-floor hydronic systems also give a completely clear floor with no registers or radiators, and provide extra comfort to the feet on otherwise "cold" surfaces such as hardwood floors or ceramic tiles, particularly in houses with an on-slab design (i.e. no basement).

Figure 2.3: In-floor Hydronic Heating

An alternative system is to combine underfloor hydronic heating in the basement or ground floor with forced air heating and cooling on the upper floors. This gives cooling where it is needed most (the upper floors) and a warm floor in the winter on otherwise cold on or below grade surfaces. Care should be taken to provide adequate insulation between the slab and the ground to avoid excessive energy loss directly to the ground.

Heat Recovery Ventilator (HRV)
To improve the indoor air quality of your home, fresh air must be added. This is especially important if you are building a well sealed and air-tight home. The lack of a furnace will also increase your need for fresh air in the home because a furnace will draw in fresh air (through cracks, etc.) to supply air for combustion. When the furnace is not used (or used less often) there is therefore less infiltration of outside air.

A heat recovery ventilator (HRV) adds fresh air to the distribution system, but pre-heats it first by means of a heat exchanger which exchanges heat with exhaust air leaving the home. Compared to having no fresh air supply, an HRV will increase home energy consumption due to the operation of the fan. There is also a slight increase in the heating required by the heat pump because the HRV is only 60 - 80% efficient in heat recovery. You will, of course, save energy compared to having a fresh air system with no HRV.

Air Filtration

Air filters are applied to forced air distribution systems. The filter is usually mounted ahead of the fan and heat pump heat exchanger to protect them from undue build-up of dust and lint, which would block airflow and negatively impact on performance.

There are several types of filters to choose from and these vary as to their cost and efficiency. The cheapest, and most common are the standard fibreglass disposable filters. These give less than 10% filtration efficiency. Similarly, low filtration efficiency is achieved with "medium efficiency" pleated filters and passive electrostatic filters. Charged media filters and upgraded 25 mm and 100 mm filters give better filtration efficiencies - up to about 50%. The highest filtration efficiency for home application is obtained with an electrostatic precipitation filter (ESP). These give up to 90% filtration efficiency. HEPA filters give even higher efficiencies (approaching 100%), but for residential application the pressure drop across this unit is too high. They are usually installed as by-pass filters, yielding only up to 50% filtration efficiency for the overall duct flow.

Filters only remove dust from the ducted air, and this is not the only air moving and circulating in your home. The air blowing from the registers will move surrounding air and dust as well. An upgrade to even the most efficient filters available will reduce airborne dust in the home by no more than 40%.

Controls
For control of your EES you can choose either a conventional heat pump thermostat or a programmable thermostat.

Conventional Thermostats
These thermostats are simple devices that determine whether the heat pump should be on or off depending on whether the home temperature exceeds or comes below a pre-set desired temperature. Changeover from heating to cooling and vice versa can be automatic giving a simple "set and forget" type of unit.

If your EES is a hybrid unit or multiple capacity compressor EES, the thermostat will have a 2-stage or 3-stage heat capability, so that the additional capacity steps or supplemental heating system will operate when needed.

Programmable Thermostats
Programmable thermostats allow you to set the desired indoor temperature by time of day and day of the week. This allows you to program a temperature setback at night or while you are away, in order to save energy costs. Typically, one temperature setback period a day will save you 10% and two a day will save you 15 - 20%. If you have a hybrid system, setbacks will not be as advantageous, and may actually result in higher energy costs. This is due to the higher energy input needed for the home to regain the original temperature after the setback period is over. If the EES is at its capacity limit, the supplementary heating system will start, increasing energy consumption and cost. This should also be remembered with a conventional heat pump thermostat, where a manual setback may not be advantageous. Some programmable thermostats give preference to the heat pump during the recovery period after setback, optimizing system operation, but it may be just as beneficial to set a comfortable temperature and not use set-back in a new well-insulated home.

Humidifier
Homes with an EES do not require the same humidification in the winter as gas or oil fired furnace heated homes. Air is not being drawn from the home by the combustion process, so there is less infiltration of dry outside air. The addition of an HRV to your home may change this, since more dry outdoor air will be admitted. This will be less of a problem if the HRV is the type that recovers moisture from the exhaust from the home.

If you decide to install a humidifier as part of your EES, you should specify a non-bypass type rather than a bypass unit. This is because a bypass unit will lower heat pump performance as well as lower the quantity of air supplied to the home.

For hydronic heating systems a separate humidifier such as a portable unit may be a good idea, especially if you are specifying an HRV for your new home.

Operating Costs
An EES will, in general, cost much less in energy than a conventional heating and cooling system or an equivalent air-source heat pump. An EES may cost you more than a conventional system with no cooling, because of the extra cost of year-round operation. Remember that your electricity bill includes usage of lights and appliances. Continuous indoor fan use can result in high electricity bills as well. Figure 1.7 (previous chapter) illustrates the relative annual heating costs of with an EES compared to various alternative systems in three locations across Canada.

EARTH ENERGY SYSTEMS FOR AN EXISTING HOME

Existing Site and Services

Access To Site
First, it is necessary to make sure that a drill rig or trencher can access the site. These are fairly large pieces of equipment: a drill rig is usually truck-mounted and trenching is often done with a backhoe. If there is no apparent easy access, see if a fence can be moved or an alternate access route found.

Adequacy of Existing Electrical System and Ductwork
The existing electrical service should be checked to see if it has the required amperage to meet the demands of the heat pump, water pumps, and fans, in addition to the home's normal load.

If the existing ductwork is going to be used as the distribution system, it should be checked to ensure adequate size because EESs require higher air flow rates due to a lower air delivery temperature than combustion furnaces. Typically the air flow rate should be 50 to 60 L/s per kilowatt of installed heat pump capacity. The fan and/or fan motor or pulleys may have to be changed to give the higher flow rate and if the ductwork is too small, there will be problems with excessive noise and fan energy consumption. In this case the ductwork should be enlarged where necessary and the fan upgraded. Your contractor can advise on the need to install an acoustic liner to absorb heat pump and fan noise.

Site Services
A thorough check into the location of underground services is essential. This includes the location of the gas mains, water mains, electrical and telephone services, and sewers. The location of adjacent property lines should be accurately established as well as the positioning of easements and required property setbacks. Domestic water wells on adjacent properties may be affected by a groundwater EES, similarly, the adjacent wells may also impact the performance of the groundwater EES.

Effect on Landscaping

The installation of an EES will cause some disturbance to the landscaping surrounding your home. Once installed, there should be no indication of the presence of the ground heat exchanger. Backfill in trenches must be adequately compacted to avoid ground settlement and an uneven lawn or garden surface.

Impacts on Adjoining Structures
An EES should be designed to avoid interference with adjacent structures, trees, walls, overhead wires, and other landscaping features. Give consideration for the space needed for the trenching or drilling equipment, and the material removed. Also, no part of the system or excavation material should cross a property boundary without the written approval of the other land owner. It is important that the heat exchanger piping of an EES does not cross other underground services such as gas and water mains, telephone lines, electric power supply, sewer, drains, etc., without protecting these from damage or freezing. EES piping must not be placed under a septic tank or cross the septic system's drain. EES piping should be placed away from other services to avoid damage during repair operations. The contractor should follow the latest CSA 445 Standard(Design and Installation of Earth Energy Heat Pump Systems for Residential and Other Small Buildings) for all aspects of the EES installation.

System Design for an Existing Home

Optimum System Sizing for Efficient and Economic Operation
An improperly sized heat pump and ground heat exchanger can impact on the system first cost, operating cost and comfort. If the EES is replacing an old central air-conditioner and it has provided comfortable air-conditioning, an EES with the same cooling capacity is a good starting point for system selection. It may be advisable to increase the capacity by as much as an additional 25 percent over that of the old central air-conditioner. This will give good heating performance and should not negatively impact on cooling comfort. The contractor must do an accurate ground heat exchanger size calculation for your home and should use one of several computer programs available for that purpose. Most manufacturers have proprietary computer programs for system sizing.

An existing home's utility bills and knowledge about the existing heating system can also be used to estimate the size of the heat pump. Some contractors may ask for this information to assist in the system sizing. Many local electric utilities offer a heating and cooling equipment sizing service at a cost and can provide estimates of operating costs, as well.

Alternatives for a Hot-water or Electric Baseboard Heated Home
An EES can be connected to an existing hot-water (hydronic) heating system through the use of a water-to-water heat pump. The EES will not be able to cool with such a system, however, since there will be serious condensation problems on the radiators. To benefit from the cooling capability of an EES, a separate forced air system should be installed. If you have a home that is heated entirely by electric baseboard heaters, you will have to add a new heat distribution system for the EES. At this point you have a choice between hydronic and forced air similar to that of a new home builder. The difference is that space may be more of a limitation in an existing home than in a new one. This gives an advantage to hydronic systems since they take up less space and cause less disruption than forced air system installations. If you are also planning to upgrade your floors, note that in-floor hydronic heating can be fitted under a new flooring material. This reduces the cost by combining work and provides an obstruction-free interior (no radiators or registers). In-floor heating gives a high level of heating comfort, but, again, cannot be used for cooling. There is growing interest in separate systems, with hydronic in-floor heating on the ground or subgrade floors and forced air heating and cooling on the upper floor or floors. With an EES this will require a water-to-water heat pump with an air handler and a hydronic coil.

Possible Upgrades

DHW Heating by Heat Pump
The heat pump can be integrated with your existing domestic water heater to provide a significant portion of your hot water requirements with lower operating costs.

Most earth energy heat pumps can be ordered with a desuperheater. This is a heat exchanger installed in the EES box which transfers heat from the heat pump to the DHW. Desuperheaters only heat water when the compressor is running. It is more likely to provide all the hot water on the coldest winter days or hottest summer days (when the unit is running), than in the spring or fall when the unit is not operating at all times. Installation of piping and a circulator pump between your domestic hot water tank and the EES box is all that is required. Desuperheaters add to the installed costs but save enough in domestic hot water heating to return the extra cost in savings in about 5 years.

Other, more sophisticated "on demand" water heaters are available on some EES heat pumps. These can heat hot water, as required, whenever there is no space heating or cooling demand. They also heat water during space heating and cooling operation. Installed costs are higher than a desuperheater, but hot water heating savings are greater resulting in a similar payback period.

Upgrading Air Filters
It is likely that your existing forced air system is equipped with the standard fiberglass disposable filters that give less than 10% filtration efficiency. These can be upgraded to charged media filters or 25 mm or 100 mm filters giving a filtration efficiency of up to about 50%. Electrostatic precipitation filters (ESPs) give up to 90% filtration efficiency but also produce measurable quantities of ozone, which is considered a pollutant at ground level. HEPA filters are another option with a filtration efficiency approaching 100%, but due to their high pressure drop are usually installed as by-pass filters in residential applications, reducing filtration efficiency to 50% in the duct flow itself.

It should be noted that filters only remove dust from the ducted air steam, and that this air, as it is released through registers, moves the surrounding air and dust as well. Thus an upgrade to even the most efficient of filters will only reduce airborne dust in the home by up to about 40%. Air filtration is not a substitute for regular vacuuming and cleaning.

Adding a Heat Recovery Ventilator (HRV)
You can improve the indoor air quality of your home by adding a heat recovery ventilator (HRV). This is a good idea especially if your EES is replacing an oil or gas furnace, because there will no longer be the infiltration of outdoor air inherent in the combustion process. Adding an HRV is also a good idea if you are improving the sealing and insulation of your home at the same time as adding an EES. A "tighter" home, like an R-2000 home, will admit less fresh air, warranting a separate fresh air distribution system incorporating an HRV. A heat recovery ventilator adds fresh air to the home, but pre-heats it first using an air-to-air heat exchanger which transfers heat from an equivalent flow of air leaving the home. Thus the air balance in the home is maintained and 60 - 80% of the sensible heat is recovered. Relative to the case of no fresh air system, an HRV will add to your energy cost due to the electrical consumption of the integral fan, and a slight increase in load on your heat pump. Compared to a fresh air system with no heat recovery, however, an HRV will save you in energy costs and reduce the load on the heat pump. An HRV can be integrated into your existing forced air system or added as a separate system to your home.
If you are changing to an EES from a gas or oil furnace system, your need for a humidifier will decrease since the dry outside air being drawn in to meet the combustion demands of the furnace will no longer be a problem.

If you plan on installing an HRV, the amount of dry outside air entering the home increases and a humidifier may become necessary. If you are using your existing forced air distribution system with your EES, and the forced air system is equipped with the standard bypass type humidifier, it would be better to replace this unit with a non-bypass type. A bypass unit will lower the performance of the heat pump and will also reduce the quantity of air delivered to the registers. If you have a hydronic system, and are keeping it as your heating distribution system, a portable humidifier may be an option, particularly if you are adding an HRV to the home.

Changes or Upgrades to the Thermostat
The existing conventional single-stage thermostat must be replaced with the heat pump thermostat supplied with the EES. This thermostat will indicate when the supplemental heat is on. Another option worth considering is an upgrade to a programmable thermostat. Programmable thermostats allow you to set the desired indoor temperature by time of day and day of the week. This allows you to program a temperature setback at night or while you are away, to save energy. Typically, one setback period a day will save you 10% and two a day 15 - 20% of your heating bill. With a hybrid or multiple stage heating system temperature setback may not be so advantageous. The back-up furnace or electric resistance heaters may operate during warm-up after the setback period, offsetting the fuel savings advantage of setback. Some thermostats give preference to the heat pump during recovery from setback and help to optimize performance of the hybrid system.

Decommissioning the Existing Equipment
If the existing furnace is not going to be left as a back-up system, you must make sure that it is removed at the conclusion of the contract. Equally important is the proper disconnecting and capping of the gas line, or the removal of the oil tank, filler, and cementing of the filler hole. Be sure to cancel any supply or service contracts for fuel.

CONTRACTOR SELECTION, MAINTENANCE AND TROUBLE-SHOOTING

What to Look for in an Earth Energy Contractor
The best way to ensure that you get a good, honest and reliable contractor is to find out from others what contractor they used and how satisfied they are. Try to get the names of at least two recommended contractors and obtain at least two quotes for the work, for comparison purposes. If you have no initial recommendation from others, you could check-out the preferred contractors with the local Chamber of Commerce, or with system manufacturers, as a first step. Make sure that the contractor is both qualified and experienced in installing earth energy systems.

A Basic Contract Specification
Once you have selected the contractor, a detailed contract specification is recommended, with proper breakdown of each job, what is involved, and the equipment, material and labour cost associated with each one. This should include the responsibility for re-landscaping and internal re-finishing, as the job is not complete until this work is done. The contract should include calculating the heating and cooling load for the home, any changes needed to ductwork, fans or filters, required electrical system upgrades, installation and start-up of the EES. The refurbishment or decommissioning and removal of existing equipment might also be part of the specification. It should also be clarified as to who is responsible for acquiring the approvals and certifications for the job. Warranty terms should also be clearly specified for a proper contract comparison. Most EES heat pump units are covered by a one year warranty on parts and labour; five years on the compressor. Finally, make sure that the contractor is adequately insured for the work. Adequate insurance means that the contractor is covered for at least $1 million in damages per major event (drilling boreholes or trenching, installing heat pump unit, etc.).

Filter Maintenance and its Effect on Equipment Life
Perhaps the most important maintenance item with any heat pump is regular filter changes or cleaning. The type of maintenance action depends on the filer type. Electronic air cleaners have pre-filters and electrostatic cells. The pre-filters and electrostatic cells may require cleaning in a dishwasher as frequently as every few months. In some cases cleaning every 30 days may be necessary depending on the activities in the home. Be certain to wash all cells and pre-filters - some electronic air filters have more than one.

There are a variety of filters available today from building supply centres. Conventional throw-away fiberglass filters are the least effective and the cheapest; to the more expensive electrostatic throw-away filters that have similar filtration performance to electronic air cleaners. The latter are expensive and good for up to three months before requiring replacement. There are aluminum mesh filters and other media types that can be cleaned. Some require a spray coating be applied after cleaning. Filter maintenance is critical to heat pump life expectancy and is something which can be done by the homeowner. Filters can plug-up, severely restricting airflow through the heat pumps indoor heat exchanger and raising the indoor coil refrigeration pressure and temperature in heating and lowering it in cooling. This puts more stress on the compressor and will shorten its life and impact on performance, as well. Failure to clean filters could void a warranty.

Maintenance and Trouble-Shooting by Owner

Table 4.1: EES Owner's Trouble-shooting Table. Click here to view the table.

Note: If in doubt, call your installing contractor to be sure. The unit should come with directions when delivered and installed.

Servicing Requiring a Contractor
There will be times when your EES will require contractor service. For example, if the indoor heat exchanger requires cleaning (it shouldn't with proper filter maintenance) this should be done by a contractor.

Other occasions will be when (see Table 4.1):

• the back-up system is not working in cold weather and there is insufficient heating and all breakers/switches are properly set;
• the service or auxiliary light is on at the thermostat in mild weather. This could mean that the heat pump has failed (Make sure you check the other possible causes before calling the contractor);
• the unit operates longer than normal in either heating or cooling. It could mean you have a refrigerant leak. If so, the leak must be repaired and the unit recharged.
• there is an unusual noise in the heat pump room coming from the piping. This could be air in the loop indicating an anti-freeze solution leak which should rectified by the contractor. (Pressure gauge on loop, if equipped, will be reading lower than normal).

Table 4.1 is intended to give you insight into problems and possible causes, many which you can check yourself before calling the contractor.