Refrigeration Air Conditioning And Heat Pumps Pdf
Terresa Cherrie
There are three main types of heat pumps connected by ducts: air-to-air, water source, and geothermal. They collect heat from the air, water, or ground outside your home and concentrate it for use inside.
Today's heat pump can reduce your electricity use for heating by approximately 65% compared to electric resistance heating such as furnaces and baseboard heaters. High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months.
Air-source heat pumps have been used for many years in nearly all parts of the United States, but they've not always been used in areas that experienced extended periods of subfreezing temperatures. However, air-source heat pump technology has advanced so that it now offers a legitimate space heating alternative in colder regions.
In addition, a special type of air-source heat pump called a "reverse cycle chiller" generates hot and cold water rather than air, allowing it to be used with radiant floor heating systems in heating mode.
Geothermal (or ground source) heat pumps have some major advantages. They can reduce energy use by 70%-80%, control humidity, are sturdy and reliable, and fit in a wide variety of homes. Whether a geothermal heat pump is appropriate for you will depend on the size of your lot, the subsoil, and the landscape.
They are different from compression heat pumps that are driven by mechanical energy and can be driven with a wide variety of heat sources such as combustion of natural gas, steam solar-heated water, air or geothermal-heated water.
Unlike standard compressors that can only operate at full capacity, two-speed compressors allow heat pumps to operate close to the heating or cooling capacity needed at any particular outdoor temperature, saving energy by reducing on/off operation and compressor wear.
Two-speed heat pumps also work well with zone control systems. Zone control systems, often found in larger homes, use automatic dampers to allow the heat pump to keep different rooms at different temperatures.
The variable-speed controls for these fans attempt to keep the air moving at a comfortable velocity, minimizing cool drafts and maximizing electrical savings. It also minimizes the noise from the blower running at full speed.
Another advance in heat pump technology is the scroll compressor, which consists of two spiral-shaped scrolls. One remains stationary, while the other orbits around it, compressing the refrigerant by forcing it into increasingly smaller areas.
Compared to the typical piston compressors, scroll compressors have a longer operating life and are quieter. According to some reports, heat pumps with scroll compressors provide 10 to 15F (5.6 to 8.3C) warmer air when in the heating mode, compared to existing heat pumps with piston compressors.
Although most heat pumps use electric resistance heaters as a backup for cold weather, heat pumps can also be equipped in combination with a gas furnace, sometimes referred to as a dual-fuel or hybrid system, to supplement the heat pump. This helps solve the problem of the heat pump operating less efficiently at low temperatures and reduces its use of electricity.
In comparison with a combustion fuel-fired furnace or standard heat pump alone, this type of system can also be more economical. Actual energy savings depend on the relative costs of the combustion fuel relative to electricity.
Even with the impressive performance of heat pumps, the U.S. Department of Energy (DOE) is still researching ways to make heat pumps more affordable and efficient. To that end, DOE launched the Residential Cold Climate Heat Pump Technology Challenge in 2021 to accelerate deployment of cold climate heat pump technologies.
So, what are heat pumps? Well, they're integral components of a home's heating and cooling setup and are typically installed outside the house. A heat pump serves a dual purpose: it can both cool and heat your home. During colder seasons, it extracts warmth from the chilly outdoor air and channels it indoors, while in warmer months, it removes heat from indoor air to keep your home cool. Operating on electricity, heat pumps utilize refrigerant to facilitate the transfer of heat, ensuring year-round comfort. Their versatility means homeowners may not require separate heating and cooling systems. In regions with colder climates, an electric heat strip can augment the indoor fan coil for enhanced heating capabilities. Unlike furnaces, heat pumps don't rely on burning fossil fuels, thus offering an eco-friendlier heating and cooling solution.
Air conditioning is a process that involves the removal of heat and humidity from indoor air to provide a cooler and more comfortable environment. It operates through a system comprising various components, regardless of the specific design of the air conditioner. The process starts with a compressor, which elevates the pressure and temperature of a chemical refrigerant. This heated gas is then sent to the condenser coil, where it undergoes a phase change into a liquid state, releasing heat to the outdoor environment. The now-liquid refrigerant travels indoors to the evaporator coil, where it evaporates, absorbing heat from the indoor air. A fan blows air across the cold evaporator coil, cooling it, and distributing the cooled air throughout the space. Meanwhile, the heated refrigerant gas is returned outside to the compressor, and the cycle repeats until the desired indoor temperature is achieved. Essentially, air conditioning works by transferring heat from inside to outside, creating a cooler indoor atmosphere.
When looking for an HVAC system to cool your home, either a heat pump or air conditioner will do the job. Both systems use compressed refrigerant to collect heat from inside your home as air passes over the coil in the air handler and transfer it outside. Heat pumps and air conditioners essentially move heat from inside your home to an outdoor location. It is often thought that air conditioners cool a home by producing cold air, but the truth is they cool your house by removing heat energy from the home, pumping it away to a location outside the home. Air conditioners pump heat out of a home, just like a heat pump when operating in cooling mode. See the similarities? In fact, if looking at the outdoor unit of an air conditioner and heat pump system, it would be very difficult for the average person to tell them apart. So, from a cooling perspective, minus a few technical details, heat pumps and air conditioners are essentially the same when operating in cooling mode, with no significant difference in operation, efficiency, or energy costs.
How does a heat pump work? How do air conditioners work , exactly? While essentially identical in cooling mode, heating mode is a completely different story. Air conditioners do not provide heating, but heat pumps do. Thanks to a reversing valve in the outdoor unit, a heat pump system works by extracting heat energy from outside air, even in extremely cold temperatures, transferring the heat inside the home, where it releases the heat into the air. A heat pump can heat and cool, but an air conditioner cannot, which is the primary difference between the two HVAC systems. An air conditioner is typically paired with a furnace to provide heat during the cold months. Together, an air conditioner and furnace are a complete heating and cooling system.
Although a heat pump can heat a home, when outside temperatures drop below freezing, the efficiency of a heat pump is affected as the unit requires more energy to maintain warm temperatures inside the home. Typical heat pump systems have an auxiliary electric heater added to the indoor air unit to add supplemental heat when outdoor temperatures drop. However because electric auxiliary heating Is not very efficient, the addition of a furnace can be a solution to this problem, creating a system that relies on the heat pump as the primary heat source but automatically switches to the furnace when appropriate. This Hybrid Heat technology is both efficient and intelligent.
Both a heat pump and an air conditioner are a great choice, but one might be more appropriate for you, depending on your situation. Here are some things to consider when choosing a system to heat and cool your home.
While a heat pump system has a lower cost indoor unit, the outdoor unit can come with a higher upfront cost compared to an air conditioner. When considering cost, it is important to understand the total costs to install a system that can both cool and heat your home properly. A Carrier HVAC dealer can help determine all of the costs involved.
In moderately cold outdoor temperatures, heat pump systems provide energy-efficient heating using only electricity. In these conditions they can be less costly to operate compared to systems that use more expensive heating fuel sources such as natural gas, oil or propane. As temperatures drop below freezing, the heat pump requires more energy to maintain comfort inside, reducing efficiency and increasing your electric bill. You can solve this problem by pairing a heat pump with a Carrier furnace, creating a Hybrid Heat system. However, due to the higher initial cost for the heat pump unit, a hybrid system may be more expensive than a more commonly paired system of an air conditioner and furnace.
In cooling mode, both heat pumps and air conditioners come in models with high SEER2 ratings, providing energy efficient cooling during the warm summer months. SEER2 ratings are like miles-per-gallon for a car. They give you a standard measure of efficiency so you can compare different models. The higher the SEER2, the more efficient the unit. In heating mode, heat pump efficiency is expressed in HSPF2. The higher the HSPF2, the higher the efficiency. In many ways, the energy efficiency and cost to operate factor comes down to location. In areas with moderate temperatures, a heat pump is a better option for efficient heating than in areas with extremely cold winters. If you want a higher efficiency model, be sure to select one that has been ENERGY STAR certified.
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