Reverse cycle systems use a high-capacity heat pump to heat or cool water, which is then circulated to heat or cool your home.
Question: I’m in the market for a new heating and cooling system. I’m thinking about an air-source heat pump with a reverse cycle chiller. How do they work and are they a smart option?
Answer: Standard air-source heat pumps have long been considered a good choice for many South Carolina homes because they can provide efficient heating and cooling in a single unit. Some air-source heat pumps now come with additional hardware called a reverse cycle chiller that can help improve the unit’s overall performance.
A standard air-source heat pump heats or cools a refrigerant that flows directly through an indoor coil. Air blows over the coil to heat or cool your house.
A heat pump equipped with a reverse cycle chiller works a bit differently. It heats or cools water in a small (20- to 40-gallon) insulated tank. The water then flows through the indoor coil to heat or cool your home. This additional step can have several advantages, particularly in the winter months.
On the coldest winter days, the heat output of an air-source heat pump drops just as the heating needs of your house increase. That’s why most systems are equipped with a backup electric resistance furnace. Resistance heat will keep you warm in a pinch, but it can really drive up your power bills in the process.
While it’s possible to install a high capacity heat pump capable of eliminating or greatly reducing the use of backup resistance heating, an over-sized heat pump is not an efficient way to cool your home in the summer months. A system that is too powerful will run in short cycles causing indoor temperature swings and high humidity in your home. That’s why the output capacity of a traditional heat pump is sized according to the cooling requirements of the house.
The primary advantage of a reverse cycle chiller is that it serves as a buffer, allowing the homeowner to install a high-capacity heat pump with adequate heating for even the coldest winter days, but without the associated summertime cooling problems. In the summer, the heat pump chills the water in the insulated tank to a temperature of about 40 degrees. The heat pump can cycle on and off while the chilled water continues to circulate in the coil, allowing the blower to run as long as needed to provide maximum comfort and efficiency.
In winter, the heat pump generates hot water that circulates through the coil to heat your home, and this hot water also helps the heat pump operate more efficiently during its wintertime defrost mode. During winter operation, a heat pump must regularly switch to cooling mode for a brief time in order to defrost ice that collects on the outdoor condenser coils. During this time, expensive electric resistance heat comes on or chilly air blows out of the registers. With a reverse cycle chiller, the heat to defrost the coils comes from the heated water tank, so warm air continues to blow from the registers. A reverse cycle chiller system also allows homeowners to select different types of heating for different rooms. The hot water can be pumped through a radiant floor heating system, for example, or it can be used to heat domestic water supplies.
New heat-pump systems with reverse cycle chillers cost about 15 percent to 20 percent more than traditional units. To find out if such a system is right for your home, consult a qualified heating and cooling specialist and evaluate all your options carefully before buying.
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The following companies offer reverse cycle chiller systems:
Aqua Products, (800) 840-4264
Multiaqua, (864) 850-8990
Unico System, (800) 527-0896
FOR MORE INFORMATION on traditional air-source and geothermal heat pump systems, view these articles:
“Know your heat pump options,” January 2012
“What’s new in heat pumps,” August 2011
“Geothermal heat pumps,” February 2010