Ground-Source and Air-Source Heat Pumps

Today, there are so many different options for heating and cooling your home that it sometimes gets a little confusing for homeowners. There are many things to take into consideration when choosing a new heating system: insulation levels, ventilation levels, installation requirements and costs, local fuel costs, existing HVAC system, additional comfort features, and more.

It’s best to consult with a professional heating and cooling contractor before deciding which heating system is best for you. Not only is the choice of system important, but also the sizing of these systems as well. Lots of work and expertise goes into sizing the appropriate unit for your home.

Considering that over half of all new HVAC system in the U.S. are improperly installed, it is especially important that you hire the right company to complete the job. It doesn’t matter how good the unit itself is; if it hasn’t been installed properly, none of those fancy efficiency statements will be met. Use this EnergyStar Installation Bid Comparison Checklist to help you choose the right contractor for the job.

Heat Pumps

Although there are water-source heat pumps, the two main types of heat pumps are air source and ground source. Generally speaking, a heat pump operates like an air conditioner in reverse. Instead of extracting heat from the inside of your home and dispensing it outdoors, in the winter, the heat pump reverses this process and extracts heat from the outdoor environment to heat the inside of your home. Often, a heat pump is referred to as the “outdoor unit.”

A heat pump can be used to both heat and cool a home. The main difference is that the flow of refrigerant is reversed.

Ground Source Heat Pumps – In the summer, the heat pump is an air conditioner that uses electricity to transfer heat from inside the home to the groundwater or soil outside. In the winter, the process is reversed and the refrigerant removes heat from the ground and delivers it to the home. Disadvantages of using a ground source heat pump include: complex installation, high electricity costs, and most effective in cooling-dominant areas.

Air Source Heat Pumps – This is the most common type of heat pump. If you know the general principles of how your refrigerator or air conditioner works, you basically know how an air source heat pumps works.

An air-source heat pump uses electricity, a compressor, and two coils (one inside and on outside) to transfer heat from inside to outside and vice versa. In the winter, the liquid refrigerant extracts heat from the outside and evaporates into a gas. (Remember, heat can be extracted from environments as cold as -15° C/5° F.)

The pressurized gas gives off heat to the surrounding area from the indoor coil and a blower distributes it throughout the home. Once the heat is released, the hot gas condenses back into a liquid and the process starts all over again.

In cooling mode, the reversing valve changes the direction of the refrigerant cycle. Other than the electricity needed to move the refrigerant and power the blower, the heat is always being naturally renewed. No need for fuel deliveries with heat pump systems.

Air Source Heat Pump Benefits:

• Depending on the heating system you are replacing, you could experience dramatically lower energy bills and lower emissions. Besides the electricity used to pump the refrigerant from one area to another, the heat you are extracting is alway naturally available.
• Potential tax breaks, rebates, and incentives. Click here for a list of Energy Incentive Programs for Oklahoma.
• Since the heat is gathered naturally, there is no need for fuel deliveries or replacements.
• The heat produced by air source heat pumps can be used to heat radiators, radiant heating systems, warm air convectors, and hot water.
• Not a lot of maintenance is required.
• Is often easier to install and maintain than ground source heat pumps.
• For homes without a duct system, a ductless mini-split system may be more appropriate.

How to Choose a Heat Pump

The most important things to look for when choosing a heat pump is the heating season performance factor (HSPF) and the seasonal energy efficiency ratio (SEER) ratings.  If you live in a heating-dominant climate, you should pay more attention to the HSPF rating, whereas homeowners in cooling-dominant areas should focus on the SEER rating.

Basically these two ratings measure the energy efficiency of your heat pump equipment by estimating its total electricity consumption, expressed in watt-hours. The higher the rating, the more energy efficient the equipment. Just remember, that these efficiency ratings are for naught if your heat pump is improperly installed. The most important day in the life of your heating and cooling equipment is the day of its installation.

How a Heat Pump Works

Watch this video for an in-depth explanation of how your air source heat pumps works:

How to Inspect Heat Pump System

• The heat pump or “outdoor unit,” should be mounted on a level surface above the ground.
• Do not run the heat pump in “heating” mode unless the temperature is 65° or below.
• Do not run the heat pump in “cooling” mode unless the temperature is 60° or higher.
• Check outside for damaged wires, plugs, and electrical connections and get them repaired immediately.
• Never stack anything on top of the unit.
• Make sure there is a minimum 2-foot clearance around the unit. Trim back hedges and bushes to ensure proper airflow.
• If your outdoor heat pump has a lot of debris, you can use a regular garden hose to rinse it off.
• Clean the heat pump’s condenser coils. If you do choose to DIY clean your heat pump, make sure the power is turned off at the breaker box before doing anything!

There are many problems that could arise with your heat pump. If it is short-cycling (frequently turning on and off) and causing humidification problems, you may have an improperly sized unit. If your unit is too small, you’ll never feel warm enough in winter or cool enough in summer.

When repairing, maintaining, or replacing your heat pump, the most important decision you have to make is who you hire to perform the job.

For more information on ground-source and air-source heat pumps, visit energy.gov.

For more tips on maintaining a safe and efficient heating system this winter, read our other blogs on the topic:

• Heating Winterization Checklist
• How to Seal Air Leaks Around Doors & Windows | HVAC Tips
• 5 Heating Season Tips for an OKC Winter | Furnace Maintenance
• National Furnace Tune-Up Month Maintenance Tips
• Fall Home Maintenance To-Do List 
• HVAC Maintenance Checklist for Homeowners
• How To Properly Inspect Your Air Ducts | Ductwork Diagnosis
• Guide to Healthy Indoor Air Quality

If you are having comfort problems with your heat pump or wish to discuss your repair and replacement options with a professional HVAC technician in the Oklahoma City area, call Interstate Heating & Air Conditioning today at (405) 794-8900.

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