Frequently Asked Questions (FAQ)

* Source: Airtechni and Geoconfort staff, Earth Energy Society of Canada, Hydro-Quebec and NRCan

FAQ > Questions related to the design of a geothermal system

• What size of heat pump is required?
  AA heat loss - heat load assessment will determine how much heat the building requires. The installed heat pump and supplementary backup unit must meet this load, subject to the conditions in the CSA standard. The quantity of loop must be consistent with the size of the heat pump. On average, a 3 ton unit will be sufficient for a 1,700 ft² home.
• Is the EE system designed to provide 100 percent of building heat and water heating?
  AA heat loss calculation will determine how much heat is required for both applications, but most systems are sized to meet less than the full design load and rely on an electric backup heater to provide supplemental heat on very cold mornings during the winter. In all cases, full cooling load can be met by a system.
• What is an open loop?
  AOne pipe is used to take water directly from a lake or river, or an underground well or aquifer. The water is circulated through the heat pump to extract the heat, and a second pipe is used to return the water to the same source. Standards dictate that the amount of water extracted cannot impact negatively on the ecosystem, and consideration must be given to discharge areas to avoid impacts (eg: if slightly warmer water is discharged into a lake during summer, the discharge should not be located near sensitive aquatic life).
• What is a lake loop or river loop?
  AThe pipe is anchored to the bottom of a water body of sufficient depth, and extracts heat directly from the water. The pipe must be weighted to avoid shifting, and must be protected at the point of entry into the lake to avoid being severed by ice movement in the spring. The position is determined to avoid damage from boat anchors. The amount of heat extracted from the water is so low and diffuse that there is no ecological damage to marine life or aquatic systems, even in the immediate vacinity of the loop.
• What is a vertical closed loop?
  AA drill is used to bore a cavity, into which a section of looped pipe is inserted and sealed according to provincial regulation. This configuration is the most efficient, since it extracts both solar heat from near-surface soil, as well as magmatic heat from deeper areas. This option is used when surface property is limited.
• What is a horizontal closed loop?
  AA trench of at least 4 feet depth is dug. At the bottom, the high-density polyethylene pipe is placed and the trench is carefully back-filled to avoid air pockets or damage from sharp rocks. There can be from one to six pipes placed in each section of trench, subject to appropriate spacing to allow for thermal separation. The pipe does not have to be perfectly level.
• Why is there lack of consensus over the issue of system sizing?
  AMost consumers will receive excellent performance and savings with an EE unit that is designed to provide 70-75% of the total heat loss for the building. When ambient temperatures are above the design balance point, the EE unit will provide all heating required; only when outdoor temperatures drop below that point does the EE unit require supplemental heat from an electric resistance heating element inside the unit. Most outdoor winter temperatures are above the balance point, and the EE system can provide 95% of the load if the unit is sized to 70%. Some dealers prefer to install a system that meets 100% of heat loss; this eliminates the need for supplemental heating but increases the cost of installation (more pipe is required).
• What is the difference between a closed loop and an open loop?
  AA closed loop is a continuous pipe that circulates a fluid (often with an antifreeze mixture) to extract heat from the surrounding soil or water. An open loop is, essentially, two pipes: one to suck in water that is moved through the heat pump to transfer heat, the other to take the cooled water and discharge it to the appropriate location, usually downstream from the first pipe.
• Is ductwork for air required?
  AAn EE system can heat either air or water. If air, ductwork is required to circulate the warmed air throughout the building. Due to the low temperature rise of an EE system, the volume of circulated air is higher than a combustion furnace and, therefore, the ductwork must have a higher capacity in cubic feet per minute.
• What are the components of an EE system?
  AThere are three basic sections: energy supply comes from the ground loop (or vertical or lake loop); the conversion of heat occurs in the heat pump and compressor; and the warmed energy is delivered through the circulation system (ductwork or in-floor radiant heating).
  
  
• Can an EE system heat a building without supplemental heat?
  AA system can be designed to provide 100% of heating needs on the coldest days in northern Canada, but the cost to install such a system would be excessively high. A system designed to provide 70% of a calculated heat load is the optimal sizing if there is a supplemental heating element, but there were past errors in calculating the heat loss and, consequently, some systems were under-sized. The new CSA standard for installation (C448) has been revised to overcome this deficiency.
• How long should the buried ground loop be?
  AThe length of pipe depends on two factors: the amount of heat required in the building (the more heat required, the larger the heat pump and the longer the loop must be) and the thermal transfer characteristics of the soil (dry light soil with entrained air can require three times the amount of loop to provide the same heat as wet, packed soil). Design software will calculate the amount of pipe for a specific site. An industry rule of thumb is that an average home requires a four-ton unit, which requires 400-500 feet of horizontal loop or 300-350 feet of vertical borehole for each ton (up to six pipes can be installed in a horizontal trench if spaced properly).
• Are there advantages of an open-loop system over a closed-loop system?
  AOpen-loop units usually are less expensive to install (no need for trenching or drilling) and are more efficient (the heat in the supply water is transferred without the need for antifreeze). Closed-loop units offer more security of supply (less chance of constriction of the water supply) and have no environmental impact. Often, loops operate at a lower cost than open systems due to lower pumping power required.
• What is the link between size of heat pump and length of loop?
  AThe higher the heat load (demand for heat), the larger the heat pump. The larger the heat pump, the longer the loop required.
  
  
• Can any pond be used as the heat source?
  AThe body of water must be large enough to contain sufficient latent heat to meet the demand of the building. The larger and deeper the better, but stagnant or glacier-fed bodies are not feasible.
  
  
• Can an EE system be used for radiant floors or hydronic heat?
  AThe heat pump can produce water that is hot enough for use in these applications. In most cases, it is not warm enough to be used in old-style under-the-window radiator systems.
  
  
• Where can the ground loop be located?
  AThe CSA standard does not allow pipe to be placed near septic tanks or hydro lines, and must be a minimum distance from neighbouring property lines.
  
  
• How does heat circulate if the building has no ductwork?
  AWithout ducts, the only option is to circulate heated water through a radiant in-floor configuration, or small fan coil units.
  
  
• How much groundwater does an open-loop system require to operate?
  ADepending on the heat load of the building, most units require 8 to 12 gallons per minute of water; more if the unit is heating potable / service water at the same time.
  
  
• Will my existing ductwork function with this system?
  AYour contractor can determine the ductwork requirements for your system and identify if modifications are needed.
  
  
• Does an EE system require additional insulation in the building?
  AThe lower the demand for heat, the smaller the heat pump and the lower the installed cost. Insulation, along with any energy management or conservation technique, is always the best first step in any heating system.
  
  
• Why is there supplemental heating?
  ATo reduce installation costs and provide better performance, an electric resistance heating element is included in unit to boost the heat during extremely cold temperatures. A fossil fuel furnace can also be integrated.
  
  

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