Heat Pumps
A heat pump is a machine or device that diverts heat from one location (the source) at a lower temperature to another location (the sink or heat sink) at a higher temperature using mechanical work or a high - temperature heat source. A heat pump can be used to provide heating and cooling. Even though the heat pump can heat, it still uses the same basic refrigeration cycle to do this. In other words a heat pump can change which coil is the condenser and which the evaporator. This is normally achieved by a reversing valve. In cooler climates it is common to have heat pumps that are designed only to provide heating.
Common examples are food refrigerators and freezers, air conditioners, and reversible-cycle heat pumps for providing building space heating. In heating, ventilation, and air conditioning (hvac) applications, a heat pump normally refers to a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow may be reversed. Most commonly, heat pumps draw heat from the air or from the ground.
How it works
What kind of magic does a heat pump perform to both heat and cool your air? Think of a heat pump as a heat juggler. Even in air that's below freezing temperatures, heat energy is present. When it's cold outside a heat pump extracts this outside heat and transfers it inside. When it's warm outside, it reverses directions and acts like an air conditioner, removing heat from your home.
One advantage of a heat pump is that it moves heat instead of generating heat, giving you more energy efficiency. Also, it is powered by electricity, so you can save substantially on fuel consumption. For example, a trane xl20i heat pump is among the hvac industry's most efficient, with a rating up to 19.00 seer and 9.0 hspf.
Note the heat pumps are best for moderate climates, and a supplemental heating source may be needed for lower temperatures.
What to look for in a heat pump
There are a few things you to look for in a heat pump. First, manufacturers rate the efficiency of most heat pumps in two ways: seer and hsfp ratings. Higher seer and hsfp ratings indicate a more efficient unit.
Seer: stands for seasonal energy efficiency rating, and is a ratio of how much energy (measured in btu's) is pumped outside in cooling mode divided by the electricity used (in watts) for cooling. Look for a seer rating between 14 and 18.
Hsfp: stands for heating seasonal performance factor. It calculates the ratio of energy pumped indoors for heating, to energy used for heating, but it's a more complicated equation than the seer rating because it also takes into account supplemental heating needs and the energy used to defrost the unit. Look for an hsfp rating between 8 and 10.
Heat pumps often feature options that make them more efficient. These include :
*a desuperheater coil that heats water by recycling waste heat (or on an rcc system, a refrigerant heat reclaimer that also uses the pump's extra capacity to heat water during mild winter weather).
*dual-mode compressors and motors that save energy by adjusting up or down according to the level of heating or cooling needed.
*scroll compressors that are quieter, more efficient and last longer than traditional compressors.
Many of these features can only be found on more expensive heat pumps, but they make up for the initial expense by helping heat pumps work more efficiently and save more energy throughout the pump's life.
What makes a good heat pump
The best heat pumps are very similar to regular heat pumps in a lot of ways, at least on the surface. First all heat pumps work using the basic physic principle of heat transference-the ability to absorb heat in one location and effectively transfer or transport it to another location.
With a standard heat pump this means that in winter time, warmth from the outside air is drawn into the pump and then moved and released into the inside air, warming the house. In summer time, the opposite happens-the heat in the inside air is absorbed and then transported and released into out of doors, leaving the interior cooler.
The best heat pumps are able to accomplish these two functions of heating and cooling using the less amount of energy thereby saving you and your family a bunch of money in the long run with lower utility bills.
Also the best heat pumps come in a variety of different categories: from the industry standard air source mentioned above to geothermic units like water-source and the newer ground or "earth" energy systems. These "green" heat pumps work in a similar fashion as the old air-source by collecting heat from either ground water or the earth itself and then transferring it to an air handler that distributes inside a building.
No matter what their heat source, all the best heat pumps have the five major components:
A standard heat pump consists of two separate machines that form a single recirculation system: an outside unit and an inside unit. This system allows the heat pump to transfer heat in two directions: from outside to in (for heating) and from inside to out (for cooling). A heat pump system is comprised of 5 major parts:
The compressor - this device compacts and pumps refrigerant (freon or ammonia and water) into a high pressure gas so it can absorb heat from the surrounding enviroment (air, water or ground).
The condenser is a system of coils or pipelines that transports the high pressure refrigerant and evaporates it from a gas back into a liquid.
An expansion or reversing value - reverses the whole process of the unit from heating to air conditioning and vice versa. The expansion value allows heat to move from the outside unit to inside the house or from inside the house to the outside unit.
The evaporator is another system of coiled pipes or tubing that transports the low pressure refrigerant and converts it from a liquid into a gas.
The air handler is the last in the part in the system and is basically a blower fan that moves heated or cooled air from the system into the air flow ducts of the house.
Now that you know more about how heat pumps work, you can easily start your research into looking for the best heat pump that your budget can afford and that will keep your family in comfortable surroundings.
