Weighing in at 400-percent efficiency and up, heat pumps are reliable workhorses which easily top furnaces for heat output per energy consumed and outpace window and wall heat pump and A/C systems by great strides. Heat pump systems are generally more popular in regions with warmer winters compared to the greater Chicago area. With advances in heat pump technology and additional features, however, heat pump systems often make the best choice for Chicago area homeowners seeking energy savings and the all-year comfort of smooth heating and cooling.
Take a few moments to explore the diversity of heat pump options and features, such as almost-free water heating, supplemental dual-fuel heating with furnaces and ductless space heating for room additions, bonus rooms and more. You may find that a heat pump system beats many other heating and cooling options by much more than a nose.
Types of Heat Pumps
Heat pumps are versatile in their heating and cooling capabilities and also in their design. While all heat pump systems use refrigeration principles of heat transfer for heating and cooling, the method in which heat transfer is applied differs by design. These are the types of heat-pump systems available:
- Air-source systems, sometimes called air-to-air heat-pump systems, extract the heat-energy from one location (e.g. inside your home in cooling mode), and transfer and release the heat energy to another location (e.g. outside your home). Air-source systems are available as split systems with one heat exchange coil located inside the home and the other heat exchange coil located outside the home. A packaged unit is also popular when space is limited.
- Geothermal systems use the earth, either ground or water, to exchange heat with household air. For instance, a vertical loop geothermal system is composed of long refrigerant tubes installed vertically within the ground, saving land area. In cooling mode, heat's extracted from household air at the heat exchange coil and released from the refrigerant coils deep within the ground. Geothermal systems are the most energy-efficient heat pumps available, since the earth and groundwater maintain consistent temperatures no matter what the outside temperature is. So, when the outside temperature is five degrees below zero during a Chicago area winter, a geothermal system is able to provide ample heat.
- Dual-fuel systems are popular in cold winter regions like the greater Chicago area. Dual-fuel heat pumps, sometimes called hybrid systems, are composed of a heat exchange coil installed with a fuel-burning furnace, such as natural gas. When temperatures are moderately cold but still above the freezing point, the heat exchange coil of the heat pump is utilized for home heating, as this is typically less costly than burning fuel. When temperatures drop too cold for air-source heat pump heating to be economically beneficial, the furnace takes over the heating chore. During the cooling months, the heat exchange coil cools the home just like an air conditioner.
- Ductless mini-split heat pumps are redesigned air-source systems with compact components which utilize a thin conduit and multiple smaller air handlers, if needed, to provide cooling directly to the required living spaces without the need for bulky ductwork. These ductless systems are excellent choices for heating and cooling room additions, home offices, bonus rooms, retrofitted areas and any spaces which are traditionally difficult to keep comfortable.
- Reverse cycle chiller systems use the same refrigeration principles of heat exchange to heat water in existing radiant floor heating systems. If you're a fan of radiant floor heating, investigate energy-efficient heat pump solutions.
How Heat Pumps Work
Heat pumps implement refrigeration principles to provide energy-efficient and comfortable heating and cooling for homeowners. Heat transfer by the manipulation of refrigerant takes advantage of the fact that heat energy of warmer air naturally wants to move to a cooler location. In the case of heat pump cooling, the hot refrigerant in the outdoor heat exchange coil will naturally move to outside air, even when outside air is very hot because the refrigerant is even hotter/
Optimal refrigerant charge and unrestricted airflow are required for peak performance and lower cooling and heating bills. While some operations and components involved for heat transfer differ from one heat pump design to the next (e.g. air-to-air heat exchange as opposed to earth-source heat exchange), the refrigeration principles are the same.
The following step-by-step process of heat exchange for heat pump heating is outlined below in terms of air-source and dual-fuel heat pump operation, which are the two most common types in our service area of greater Chicago, northwest Indiana and southwest Michigan:
- A thermostat signals the heat pump for heating.
- The compressor located in the outside cabinet squeezes refrigerant in preparation for heat exchange.
- The high-pressure vapor refrigerant flows to a reversing valve, a device which allows heat pumps to both heat and cool a home, and is directed to the indoor heat-exchange coil (evaporator).
- The high-pressure vapor refrigerant flows into the evaporator and is condensed into liquid form.
- An indoor air handler pulls air across the evaporator, which helps instigate the hot refrigerant to release heat into ducted airflow.
- The air handler forces the warmed airflow through the supply ducts to the living spaces.
- The air handler continues circulating airflow for the duration of the heating cycle, so that cooler return air is pulled into the return ducts to complete the airflow circulation process.
- The refrigerant flows out of the evaporator and back to the reversing valve where it's directed to the outside heat exchange coil (condenser).
- As the cooled liquid refrigerant enters the evaporator under low pressure, it vaporizes with the help of another air handler pulling air across the coil.
- The refrigerant becomes very cold during this phase of transforming to a vapor, which allows the refrigerant (based on refrigeration principles) to extract heat from outside air, even when the temperature of the air dips near the freezing point. (In dual-fuel heat pumps, when the temperature is near the freezing point, or the heat pump's balance point, a gas-fueled furnace activates to take over the primary heating duties.)
- The low-pressure vapor refrigerant leaves the condenser and flows back to the compressor to be prepared once again to repeat the heating process.
This heating cycle will repeat until the thermostat set point is reached. For new heat pump systems with advanced features, the heat pump maintains indoor temperature within one degree with low-volume heating cycles for ultimate comfort and efficiency.
Sizing Your New Heat Pump
The size of heat pumps and air conditioners is referred to in “tons,” such as a 3-ton heat pump. This doesn't mean that the heat pump weighs six thousand pounds. It means that the heat pump is capable of removing the equivalent heat energy required to melt three tons of ice in a 24-hour period—an HVAC term carried over from when ice blocks, harvested by the ton, were used to cool homes and buildings decades ago.
To make sure your heat pump upgrade is the correct size required to remove or transfer the right amount of heat energy from your home, a heating and cooling load must be performed by your HVAC contractor. Your HVAC pro should use a Manual J software program, the industry standard, published by the Air Conditioning Contractors of America (ACCA).
Manual J is recognized coast to coast for delivering accurate calculations for achieving optimal indoor environmental conditions by sizing equipment properly. There are a plethora of calculations performed regarding your home's square footage, area of walls and ceilings, orientation to the sun, number of occupant and dozens more.
Once your HVAC pro has determined your home's heating and cooling load, you can start selecting your new heat pump based on size and features using Manual S from ACCA. Your HVAC professional should discuss various advanced features with you that will actually help reduce your practical heating and cooling load by providing more efficient airflow and precise temperature control.
These are some of the advanced features available with high-efficiency heat pumps:
- Variable-speed air handlers utilize near endless speeds to precisely control the amount of airflow based on real-time temperature needs as received from the thermostat. Variable-speed air handlers are a must-have feature if you're installing a zoning system for personalized temperatures throughout your home.
- Desuperheaters are add-on heat exchangers which provide cost-effective water heating by using exhaust heat energy from the heating and cooling process, which would otherwise be wasted energy and energy dollars.
- Two-stage compressors are able to pump exact amounts of refrigerant to optimize the heat-exchange process.
- Thermal expansion valves (TXVs) precisely control the total amount of refrigerant which flows into the heat exchange coil. This helps high-efficiency heat pumps achieve optimal comfort levels inside the home when combined with other advanced features for optimizing airflow.
If you'd like more information about heat pumps and how they may work in your home, contact Comfort24-7. We're proud to serve homeowners in and around greater Chicago, northwest Indiana and southwest Michigan.