Air Source Heat Pumps

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Air Source Heat Pumps

Find out if this energy efficient, totally green system is for you

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Geothermal Heat Pumps: Save Ten With Angie's List!

If you live in a relatively temperate climate, you should give air source heat pumps some consideration.

There have been many recent advances in this technology, making them a viable alternative to ground water source heat pumps.

Although air-source heat pumps can be used in nearly all parts of the United States, they do not generally perform very well over extended periods of time, in regions of the country that experience sub-freezing temperatures.

There are systems available in today’s market that allow combination fuel sources so when the temperatures are below 40 degrees F., a gas component takes over the heating cycle.

Air Source Heat Pumps - Split System

Air Source Heat Pumps - Split System

Air Source Heat Pumps - Components:

The air source heat pump consists of a compressor, an interior coil, and an exterior coil. Each of these coils are made from copper tubing and each is surrounded by aluminum fin material to aid in the heat transfer process.

When the heat pump is in heating mode, liquid refrigerant is pumped through the exterior coil, which extracts heat from the air and it evaporates into a gaseous state.

When the gas enters the indoor coil, it releases heat from the refrigerant as it condenses back to a liquid state. In the cooling mode, there is a reversing valve that reverses the process.

Efficiency suffers when the outdoor temperatures fall much below 40 degrees F. Under these circumstances, the unit usually goes into full resistance heating mode and the efficiencies drop dramatically.

Keep in mind however, that today's heat pumps are much more efficient that those 25 to 30 years ago. They are from 1.5 to 3.0 times as efficient, so progress is being made with this technology.

Geothermal Heat Pump Showing Closed Loop In The Ground

Air Source Heat Pump - Packaged Through Wall System

Air Source Heat Pumps - Efficiency Advancements::

Some of the advancements that contribute to the efficiency are:

Thermostatic expansion valves for more precise control of the refrigerant flow to the indoor coil

Variable speed blowers, which are more efficient and can compensate for some of the adverse effects of restricted ducts, dirty filters, and dirty coils.

Improved coil design

Improved electric motor and two-speed compressor designs

Copper tubing, grooved inside to increase surface area.

As with the typical gas-fired furnace, most air source heat pumps are referred to as split-systems, in that they have indoor and outdoor components.

These units have an indoor coil and an outdoor coil, supply and return air ductwork and there is a central fan for the system.

There are also packaged units where both coils and the fan are located within the same unit. These are also referred to as through-wall units and are used to heat just one smaller space, similar to a hotel room.


Geothermal Heat Pumps - Compresson and Heat Exchanger Coil

Air Source Heat Pumps

How to Select an Air Source Heat Pump:

First of all, look for the EnergyGuide Label, which every unit is required to have.

This label will give you a listing of features for the unit and the units heating and cooling efficiency performance ratings, allowing you to compare it to other systems. comparing it to other available makes and models. Here are some of the ratings and their definitions:

HSPF: This is the Heating Season Performance Factor. This is the total space heating required during the heating season in BTU's, (BTU - British Thermal Units), divided by the total electrical energy consumed by the unit during that same period of time. The most efficient units will have a HSPF between 8 and 10.

SEER: This is the Seasonal Energy Efficiency Ratio. This is the total heat removed from the space during the cooling season in BTU's, (BTU - British Thermal Units), divided by the total electrical energy consumed by the unit during that same period of time. The most efficient units will have a SEER between 14 and 18.

Geothermal Heat Pumps - Ground Coil In Place for a Closed Loop System

Air Source Heat Pumps - How They Work

Air Source Heat Pumps - Look For The Energy Star Label:

To quickly find the most efficient units look for the DOE EnergyStar Label. This rating is assigned to Air Source Heat Pumps that have an SEER of 12 or greater and HSPF of 7 or greater. The higher the ratings numbers, the more efficient the unit will be.

Air Source Heat Pumps - Additional Factors To Consider:

These are some other factors to consider when choosing and installing air-source heat pumps:

Demand-defrost control. This feature will minimize defrost cycles and reduce energy consumption. Much like a condensing unit for a typical air-conditioning system, the outdoor component houses fans.

Fans make noise so carefully select the unit location to control the noise factor.

Protect the outdoor unit from high winds. It should be located in a shelter position to get the highest efficiency out of the unit.

Refrigeration systems should be leak-checked at installation and during each service call.

When installing the system, made sure you use a contractor that is very familiar with Air Source Heat Pump systems.

According to a report funded by EnergyStar, more than 50% of all heat pumps have significant problems with low airflow, leaky ducts and incorrect refrigerant charge. Most of these problems point directly at an improper installation.