Heat Pumps

Standard Air-to-Air Heat Pumps

If you’ve moved into a home with a standard air-to-air heat pump and you have no operating instructions, these links will give you basic information on how your heat pump works and how best to operate it

For specific details on your heat pump, please contact the manufacturer

(The following content was repurposed from “Using Your Heat Pump to Save Energy and Money: A Basic Guide PDF)

Heat Pump Basics

If you’ve moved into a home with an electric heat pump and you have no operating instructions, this basic information explains how your heat pump works and how best to operate it. For specific details on your heat pump, please contact the manufacturer.

In the Event of an Outage

What should you do if you experience a power outage lasting longer than 30 minutes in the winter? When power is restored, allow the heat pump to heat your house for about one hour in the emergency heat setting. This will allow the compressor heater to warm up any refrigerant that may be in the compressor. After an hour has passed, you may switch your thermostat back to normal heating.

On many newer heat pumps, this procedure is not required; ask a heating contractor to be sure you know what steps, if any, are required for your unit.

How Your Heat Pump Works

Any appliance that takes heat from one area and moves it to another is a heat pump (like a refrigerator or freezer).

Most heat pump installations involve what is called a split system. The outdoor unit contains the compressor and a heat exchanger, called a coil. The indoor unit contains another coil, a return grille, electric heating elements, and a fan that blows air through your duct system.

The outdoor and indoor units are connected by copper tubes that move a gas refrigerant (such as Freon) between the indoor and outdoor coils. This refrigerant has the ability to absorb heat from the air, even at very low temperatures.


In the winter, the refrigerant absorbs heat from outdoor air drawn across the outdoor coil. The refrigerant becomes hot but is made even hotter (in excess of 140º F) by going through the compressor.

This hot gas travels through a copper tube to the indoor coil. The fan draws air through your return grille and pushes the air across the indoor coil. The hot gas transfers its heat to the air blown across the coil and into the duct system.

  1. Outdoor coil extracts heat from outdoor air.
  2. Refrigerant gas carries heat to indoor unit
  3. Circulating indoor air picks up heat and carries it throughout the home


In the summer, your heat pump simply reverses the flow of refrigerant to absorb heat from room air blown across the indoor coil. This process removes heat and humidity from the indoor air and distributes cool, dry air throughout your home.

The absorbed heat is carried by the refrigerant through the copper tube to the outdoor unit where it goes through the compressor and the outdoor coil, which transfers the absorbed heat to the outdoor air.

  1. Indoor coil extracts heat from home’s air
  2. Refrigerant gas carries heat to outdoor unit
  3. Outdoor coil transfers heat to outdoor air

Set Your Thermostat Wisely

When the outdoor temperature drops below 32º F, your heat pump may need assistance in heating your home. Electric heating elements will come on automatically to help heat your home during severe weather.

Many thermostats have an indicator light that tells you when the electric back-up heat is on. (It may be labelled emergency or auxiliary.) Generally, you should see this light on only during very cold days. The light may also indicate a problem with your heat pump, such as a clogged air filter.

Setting your thermostat to the lowest comfortable temperature is the best approach to conserving energy and saving money. (SMECO recommends a temperature of 68º F during the winter.) Frequent or drastic changes to your thermostat setting may cause your back-up heat to come on and use more energy. Adjust the setting just two degrees at a time to prevent the back-up heat from coming on. Whenever your electric back-up heat comes on unnecessarily, you will be wasting energy.

When your heat pump is operating in the cooling mode, there is no back-up system. You can adjust your thermostat setting up or down without worrying about additional systems coming on. For economical operation, however, you should aim for the highest comfortable temperature when selecting your thermostat setting. (SMECO recommends a temperature of 78º F during the summer.)

There are many types of thermostats. Please feel free to contact SMECO or a heating contractor to discuss the proper operation of your existing thermostat or the selection of a new, energy-saving programmable or smart thermostat.

Don’t Neglect Your Filter

The filter is the most important item to keep up with. The filter is also the most neglected part of the heat pump—and the cause of many high energy bills! Your filter collects dust particles that otherwise would clog your indoor coil. When your filter is not cleaned or changed periodically, you run the risk of substantially increasing energy consumption, reducing comfort, and causing equipment damage.

You should clean or replace your filter every month. The filter is located in the indoor unit or the return air grille. If you can’t find your filter, call a heating contractor, manufacturer, or SMECO for assistance.

Ensure Proper Airflow

Air that has been heated or cooled is distributed throughout your home by the duct system through vents located in each room. Proper air flow is critical for efficient heat pump operation. Don’t close off more than 10% of the vents in your home. Don’t block a vent’s air flow or try to deflect its direction.

Proper air flow is also important for the outdoor unit. Keep grass, shrubbery, leaves, and dust away from the unit for unobstructed air flow.

Leaks in the duct system are the most common and serious cause of high energy bills with heat pumps. The most critical leaks are those nearest your heat pump’s indoor unit, where the air pressure is greatest and the air temperature is highest. An HVAC contractor can test your duct system and seal any leaks.

You can also download our brochure, Using Your Heat Pump to Save Energy and Money: A Basic Guide.

YouTube: See How a Clogged Filter Can Restrict Airflow Video

Watch for These Signs of Trouble

Other than changing the filter, heat pump maintenance should be performed by a qualified technician. Call an HVAC contractor when you experience:

  • Unusual sounds or noise
  • Emergency or auxiliary heat indicator light always on
  • Unit operating constantly in mild weather
  • Outdoor unit continuously iced over
  • No airflow out of registers

Geothermal Heat Pumps

A geothermal system makes efficient use of the earth’s stable temperature to provide comfortable heating and cooling in your home.

How a Geothermal System Works

During winter, standard heat pumps heat the indoors by absorbing heat from the outside air and transferring it to the indoor air through a mechanical compression cycle. This method is efficient, but it is limited because of fluctuating outdoor temperatures.

Unlike the air, the earth is very stable in temperature. In Southern Maryland, at depths from 4 to 500 feet, the average temperature is around 50 to 55º F year-round. A geothermal heat pump makes efficient use of the earth’s stable temperature. As a result, homes and businesses can be heated and cooled at maximum efficiency regardless of the outdoor air temperature.

Closed-Loop Geothermal Systems

All geothermal systems utilize a compressor, a refrigerant, and an indoor heat exchanger connected to the duct system. The only thing that may vary is the method by which the earth’s energy is absorbed and released.

The closed-loop system circulates a water and anti-freeze solution through a piping system which may be buried vertically or horizontally. This solution fills the loop and is constantly circulated by a low-wattage pump. The following is a description of the closed-loop systems most commonly used in the Southern Maryland area.

Vertical Loop

Vertical loop systems are popular for sites with limited space or with well-established yards and trees because the system disturbs minimal ground area. One loop is required for each ton of heat pump capacity. Each loop is inserted into a borehole, 150 feet deep and six inches in diameter.

Horizontal Loop

Horizontal loop systems are used when there is sufficient open space such as a field, large yard, or parking lot. Basically, the soil classification and actual available open space dictate the design. The length of pipe runs from 250 to 550 feet per ton of heat pump capacity, depending on soil conditions and loop design.

Benefits of Geothermal

  • Lowest heating and cooling costs available
  • No outdoor unit
  • Long equipment life
  • Truly renewable energy source
  • No defrost cycle
  • Low maintenance
  • Good humidity control
  • System can also be used to heat water, reducing energy costs

Since geothermal heat pumps utilize a stable energy source for heat transfer, they also heat water very efficiently by making use of excess heat energy from the compressor. This method can reduce conventional residential water heating costs by 50 percent.

No matter which loop configuration or what brand of heat pump you select, a geothermal heating and cooling system is the most energy efficient heating, cooling, and water heating system available.

Actual costs of operation will depend on the size of your home or business, selected room temperatures, and hot water consumption. But no matter what the requirements, a geothermal heating and cooling system will save you in energy costs for years to come.