Heat Pumps
By Kenton Shepard
Both air-conditioners and refrigerators are forms of heat pumps. Heat pumps take advantage of the properties of a fluid which changes easily between a liquid and a vapor. By routing the fluid through a compressor, condenser and evaporator, the heat pump is able to extract heat from the surrounding air, from the ground or from a body of water such as a pond, and transport it into a home for heating. They can also be reversed to extract heat from a home and deposit it into the air, ground or water.
Even materials which feel very cold have heat in them. Heat pumps operate less efficiently in colder climates, so payback times may be longer. Excavations costs will also affect payback times.
Types of Heat Pumps
Three kinds of heat pumps are used to heat homes…
Air-source heat pumps are the most common type. Like a typical air-conditioner, split air-source systems have an outdoor unit which includes a compressor, outdoor coil, fan and reversing valve. That unit is connected by refrigerant-filled tubing to an indoor component consisting of a fan, indoor coil and a supplemental resistance heating element. "Package" systems combine both components in a single, roof-mounted unit.
Ground-source heat pumps circulate a fluid through a system of buried tubing to gather heat from the earth, which is much more consistent in temperature than air. Across the middle of the US, the ground 4-feet deep is usually above 50 degrees F. even during the winter, so it’s a good source of heat.
Ground-source systems use a loop of tubing buried below the frost line. Fluid circulates through the tubing, gathering heat from the earth. A ground-water system typically involves pumping water from one well, transferring its heat to your house, then returning the water to another well.
Water-source heat pumps typically pump water from one well, transferring its heat to the building interior, then return the water to another well. Ponds or lakes are also sometimes used.
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Air-source heat pump
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Ground source heat pump
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Water-source heat pump
Energy-efficiency Rating of Heat Pumps
Manufacturers use two indexes for measuring: Seasonal Energy Efficiency Rating (SEER) for cooling and Heating Seasonal Performance Factor (HSPF) for heating.
Government regulations require that all newly-manufactured models have a cooling SEER of at least 10.0 and a heating HSPF of 6.85. These regulations don’t guarantee that a new unit you buy will comply since many dealers still have older, lower-efficiency models in their inventories.
Other than proper response to the call for heat, heat pumps may be a specialist inspection. This depends to some degree on individual inspector’s comfort level with them and how often they see them.
This list provided in the following link may help inspectors become more familiar with inspection requirements of heat pumps. Remember… if you’re not qualified to inspect it, say that in writing and limit your report to the response to the call for warm/cool air. Heat Pump Inspection Checklist |
