Installation Questions
How to size a geothermal heatpump for residential building? How deep should a loop be? The Canadian Standards Association (CSA) C448 standard requires that horizontal loops be buried at least 4 feet below surface. The deeper the depth the better, as thermal stability increases with depth. Many provinces demand the use of trench scaffolding if depths exceed 6 feet, which imposes a cost. Vertical boreholes have no limits on depth, although an average depth is 100-200 feet.
Is there a national / local standard to govern the installation of a geoexchange system? As of March 2002, both residential and commercial installations are covered under the Canada Standards Association (CSA) C448. We are not aware of any provincial regulations affecting Geoexchange installation, though some municipalities or other regulatory agencies may have guidelines or rules pertaining to the installation of systems. CGC members should be informed and current on all relevant standards and regulations, though as always, the burden of information falls on the consumer. We therefore recommend consumers raise the question with your local installer and local government officials, until you are satisfied that all necessary standards and regulations have been met.
Trenches are usually spaced 8-10 feet apart, while boreholes are spaced 10-15 feet apart.
Most contractors prefer to retain control over the entire job to ensure compatibility of all sections, but the digging of the horizontal trench (and backfilling) is one area that could reduce costs if done under the guidance and direction of the installing contractor.
Can a homeowner install a geoexchange system? It is recommended that a qualified and certified contractor be used to design and install the system. If a homeowner wants to save money and has access to a backhoe, the contractor may provide details on where to trench on the property, and when to backfill after the loop is installed.
How deep should the vertical borehole be drilled? Deeper is generally better, but there can be technical constraints. Most residential boreholes are 75-100 feet, but some can be as deep as 1000 feet depending on soil properties, heating requirements, and other factors.
How deep should the ground loop be installed? The CSA C448 standard directs that the minimum depth is 4 feet; the former 445 standard required 2 feet. The objective is to install the loop as far below the frost line as possible. Many provinces require safety measures when a trench is more than six feet deep, so most contractors do not exceed that depth in order to reduce costs.
Are there any concerns with joining sections of underground pipe? The high-density polyethylene pipe is socket fused (basically, melted together with a high temperature tool), which makes the joined plastic section more solid than the original resin. If done by a certified fusion contractor, there is virtually no chance of breakage or separation under normal conditions.
How many pipes should be installed in a trench? From one to six, depending on design considerations and the thermal characteristics of the soil.
What spacing is required for the ground loop? Each pipe extracts heat from the nearby soil, so separation should be as wide as possible. The CSA standard demands at least 10 feet between sections of loop, which can be reduced under certain conditions.
Does a geoexchange system use a setback thermostat? A geoexchange system relies on a constant, low level of temperature for the building, and any sudden increase in heat demand will cause the supplemental backup heating unit to activate. Setback thermostats are not recommended for use with a geoexchange system.
Is it possible to make a mistake when installing the ground loop? It is unlikely that a certified loop installer would make any mistake since he/she is trained to fuse sections of loop. The CSA standard requires that a system be tested to a pressure above normal operating levels, to determine if there are any leaks or problems which can be corrected immediately.
Is there a concern with poor-quality water in an open-loop system? In a closed-loop system, the water must be of good quality and meet the specifications of the heat pump manufacturer and the supplier of the anti-freeze solution with which it is mixed. In an open-loop system, some chemicals and minerals in the water may not be compatible with the heat exchanger. An analysis of the water should be performed before purchase to determine which model of exchanger is required. If the water content changes over time, this may have a detrimental impact on the system.
Can a geoexchange system be added to a fossil fuel furnace? A dual system can be added to an existing furnace to provide a dual-fuel heating system, where the heat pump is the main source of heating and the combustion furnace provides the supplemental heat.
Is a geoexchange system difficult to install? The ground loop can be difficult to install, depending on rocks, physical obstructions and topography. The interior heat pump is easy to install, and can be located in areas without proper ventilation (there is no combustion, so no need for exhaust). Most units are easy to install, especially when they are replacing another forced-air system. The air distribution may be difficult in a retrofit installation.
Will a geoexchange loop affect a lawn or landscape? The only impact will be a period of settling for soil that is placed back in the trench. This visual evidence takes one year to settle.
Can a geoexchange system be located in a septic bed to take advantage of the heat? The CSA standard specifically bans locating a ground loop near septic systems to avoid retarding the microbial action to decompose sewage. Grey water from the building can be used in some situations, if that collection unit is separate from the septic system.
What heat transfer fluids are permitted? The anti-freeze that is used in a closed-loop system must be approved by provincial authorities and acceptable to the heat pump manufacturer. Methanol and denatured ethanol are the most common fluids used (methanol is not approved for use in Ontario). The fluid must be mixed with water in accordance with instructions, usually on a 4:1 ratio of water-to-chemical.
Can I install a ground heat exchanger myself? It is not recommended. In addition to thermal fusion of the pipe, drilling and trenching are procedures best handled by licensed professionals. Non-professional installations may result in less than optimum performance, which could cancel out anticipated savings. Also, warranties are usually void if a non-authorized dealer installs the system.
Will trees or plants affect ground temperature or the efficiency of a geoexchange system, of vice-versa? No. Systems are installed away from trees to avoid damage to root systems when digging the trench.
How long does an installation take? Depending on soil conditions and the length and depth of pipe, a typical residential system can be installed in two days. Commercial systems depend greatly on geography and system size for accurate estimation.
What laws apply to open-loop installations? The CSA C448 standard contains a number of requirements to ensure that an open-loop unit does not abuse the increasingly valuable water resource.
Does the capacity of electrical service need to be increased with the addition of a heat pump? A contractor can advise if an upgrade is required to accommodate the additional electricity required.
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