A heat pump works like a normal central air
conditioning system. The main difference is that instead of taking the colder
months off, the unit must work all year long. When your thermostat senses a
need for cooling, the fan in the furnace or air handler comes to life. This fan
blows air over a coil containing refrigerant. The outdoor unit contains a pump
which is called a compressor. This compressor pumps the refrigerant to the air
handler where heat from the air is transferred to the refrigerant. Then the
refrigerant is returned to the outdoor unit.
Here another fan pulls air over another
coil and the heat is transferred to the outdoor air. This process is repeated
over and over until the home is cool.
To provide heat to the home a few
components are added to the basic air conditioner. A reversing valve is added
to change the direction of refrigerant flow. In the heating mode, this makes
the refrigerant temperature higher then the indoor temperature. Therefore, when
the refrigerant flows to the indoor unit, heat is transferred to the homes'
air.
When it gets below freezing outside, ice
can build up on the outdoor coil. This reduces the units' ability to provide
the required heat. Therefore, a process is required to melt this ice.
That process is called a defrost cycle.
Most units use a timer, a thermostat, or a combination of the two to control
this process. When the control senses the need, the outside fan is stopped and
the reversing valve directs the hot refrigerant to the outdoor coil. This
causes the ice to melt and the process is stopped by another thermostat in the
outdoor unit.
To keep from blowing cold air into the
home, during this process, backup heat is provided by the furnace.
If you live in an area where it regularly
drops below freezing, these units may not be right for you.
If you do live in these areas, you can use
these units. But, it is usually a good idea to have a control installed so the
unit does not run when it is freezing. This is called an outdoor thermostat.
When the outdoor temperature drops below its' setpoint, it can shut off the
outdoor unit and use the furnace to provide the required heat.
The latest thing on the market is called a
hybrid heat system. This system combines a heat pump with a gas furnace. This
control senses which type is more cost effective and switches back and forth as
conditions change.
Because these units provide both heating
and cooling, it is even more important that you have the proper size. The wrong
size unit will steal money from your pocket the whole year long. That can add
up in a hurry.
To keep the system running in the most
efficient manner, some maintenance is required. Most dealers will provide a
service contract but, with some help, you can perform the recommended
maintenance. This will also make your system last longer.