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Heat Pump FAQ | Common Questions About Heat Pumps

by vscontent on October 27, 2017

heat pumps

Despite the fact that heat pumps are used to provide cooling in the majority of homes, there are still many questions and misconceptions about them.

For instance, the term “heat pump” generally refers to an HVAC system that provides both cooling and heating, even though an air conditioner is technically a heat pump.

To help sort through all of this heat pump confusion, we’ve created a Frequently Asked Questions (FAQ) post on the topic. If you still have any questions about your heating and cooling system, visit our HVAC FAQ page or contact us (24/7) at (253) 292-3995.

Heat Pump FAQ

  1. What is a heat pump?

Although an air conditioner is technically a heat pump, the term “heat pump” generally refers to a system that provides year-round cooling and heating.

A central air conditioning system works by absorbing heat from the inside of your home and dispersing it outside. Heat from your home is absorbed via the extremely cold refrigerant in your evaporator coils. After collecting heat, the refrigerant travels outdoors to your condenser unit, where it gets rid of it with the help of a powerful fan. Learn more about how air conditioners work.

It’s useful to think of an air conditioner as a heat pump that only works in one direction—pumping heat from the inside to the outside.

A heat pump, on the other hand, works in both directions using the same refrigerant process—pumping heat from inside to outside and pumping heat from outside to inside.

When the temperatures drop outside and you need heat inside, the heat pump reverses itself to absorb heat energy from the outdoor environment to pump indoors.

While it’s possible for heat pumps to extract heat from cold environments, heat pumps are ideal for moderate climates that don’t experience a lot of cold days.

  1. How does a heat pump work in cold weather?

After learning what a heat pump is, the next logical question is “how can it absorb heat from the cold environment outdoors?” In order to answer this question, it’s necessary to go over some basic principles of science, namely the 2nd Law of Thermodynamics.

According to the 2nd Law of Thermodynamics, heat flows naturally from hot to cold.

Due to the properties of refrigerant (aka Freon®), it’s easy to raise and lower its temperature. If the temperature of the refrigerant is significantly lower than the temperature outdoors, heat can be extracted from the outdoor environment. Hence, the 2nd Law of Thermodynamics. When the refrigerant is much colder than the outside air, there is still plenty of heat to absorb when temperatures feel cold outside.

As you might expect, however, as the temperature drops, it gets increasingly difficult to extract heat. Once the air gets close to freezing temperatures (30-35°F), you will probably need a supplemental heating system to provide you with the comfort you need. Learn about hybrid heating systems.

The other main scientific principle at work is the Combined Gas Law, which combines Boyle’s Law, Charles’s Law, and Gay-Lussac’s Law.

Basically, when you increase pressure, temperature increases (think of the heat generated when inflating a tire); and when you decrease pressure, temperature decreases (think of an aerosol can getting cold when you depress the nozzle and release pressure).

By increasing and decreasing pressure on the refrigerant, the heat pump can control its temperature. To absorb heat, the refrigerant is depressurized. To release heat, the refrigerant is pressurized.

While heat pumps can be extremely energy-efficient in moderate climates, they can be energy hogs in more extreme environments. This is why some homeowners have a backup heating system (hybrid heating) to kick on when the temperatures dip below a certain point. When temperatures approach freezing levels, the backup heater (normally a gas-powered furnace or electric resistance heat strips) turns on to provide heating.

  1. Why is there a layer of frost/ice on my heat pump?

When the refrigerant flowing through your outdoor heat pump is extremely cold, it can gather a layer of frost and ice. This is natural.

It’s why every heat pump has a defrost mode. In order to melt the frost/ice, the heat pump has to occasionally reverse the flow of refrigerant so it begins to act like a traditional air conditioner again. This releases heat to the outdoor unit for the purposes of melting the snow/ice/frost. If you hear an unusual sound coming from your heat pump, it could just be the defrost cycle. If the strange sound continues after the defrost mode has turned off, contact a professional.

When your heat pump switches to defrost mode, you may experience some cool air flowing from your vents. This is simply the heat pump working to thaw your outdoor unit. Defrost mode typically lasts around 10-20 minutes. If it continues for more than 20 minutes, contact your professional HVAC technician.

If you have a supplemental heating system, it should turn on while the heat pump is in defrost mode so you have no loss of comfort. If you have a furnace or electric resistance heat strips, they will turn on while the heat pump is in defrost mode.

While a little ice and frost is completely normal, a lot is not. If you see thick layers of snow, ice, and frost on your unit, turn on your emergency heat (this is the supplemental heating system) and contact a professional technician right away.

Ice and frost should never last more than 4 hours. The defrost mode is supposed to turn on periodically to handle any built-up ice.

Occasionally, a leaking gutter above the unit can create an icing situation. Make sure there is no water runoff or leaky gutters above your outdoor unit.

Learn more about common winter heat pump problems, including frozen heat pumps, constantly running heat pumps, and heat pumps that blow cold air.

  1. What is a hybrid heating system, aka supplemental heating?

When it becomes inefficient for your heat pump to extract heat from the outside air, a supplemental heating system (known as Dual Fuel or Hybrid Heating) will kick on. The two will never function at the same time.

For instance, a gas furnace can work in conjunction with a heat pump to provide heating when the temperatures are extremely low. Other hybrid heating systems use electric-based heat or some other form of heating. If you want to save money and the environment by having the most efficient HVAC system, hybrid heat pump systems are the way to go.

One benefit of hybrid heating systems is their ability to provide uninterrupted heating when the heat pump goes into defrost mode.

Learn more about hybrid heating systems.

  1. How can I tell if I have an air conditioner or a heat pump?

The answer to this question may be harder to answer than you might think. Still, there are some simple things you can do to check:

  • Switch your thermostat to “heat” and walk outside to see if the outdoor heat pump is running. If your outdoor unit runs when the heat is one, you most likely have a heat pump, not an air conditioner. One caveat: if you have a hybrid heating system, then it’s possible that your supplemental heating system is running and your heat pump is dormant for the time being.
  • Continue your investigation by looking for a brass reversing valve inside of your outdoor condenser unit. This piece changes the direction of the refrigerant flow. If you have can look into your heat pump and see a brass reversing valve, you have a heat pump. Keep in mind, however, that some heat pumps hide this piece so that it is not immediately viewable.
  • The last and most conclusive way to check if you have a heat pump is by writing down the model number on the outdoor unit and looking it up online. The model number (M/N) should be on the manufacturer sticker located on the side of your unit.
  • Also, if you find the EnergyGuide label on your heat pump unit and it has an HSPF (Heating Seasonal Performance Factor), it is a heat pump, not an air conditioner. Only heat pumps have the HSPF rating.

If you still don’t know what type of HVAC system you have, a simple call to Pacific Heating & Cooling will do the trick: (253) 292-3995.

  1. How often should I schedule maintenance for my heat pump?

As with other HVAC systems, it’s important to schedule bi-annual HVAC maintenance—once in the fall and once in the spring. In addition to improved performance, lower utility bills, and better air quality, bi-annual HVAC maintenance will also ensure that any manufacturer warranties you have remain valid. If you read your manufacturer warranty fine print, you will see that neglecting regular maintenance will void them.

We recommend scheduling heat pump maintenance in the fall before you first turn on the heat for the colder season. This way, you can make sure the heating function of your heat pump is all set to provide you with heating service at optimum efficiency. Your HVAC technician will also catch any potential problems that could turn into expensive repairs and make sure your unit is clean for improved indoor air quality.

Additionally, make sure you call a professional technician to perform a tune-up in the spring before you first need its cooling services. Sign up for a Heating and Cooling Maintenance Plan to have these tune-ups automatically scheduled for you (plus other exclusive membership benefits)!

This equals 2 professional heat pump tune-ups every year. Learn what goes on during a professional HVAC inspection.

  1. What can homeowners do to improve heat pump performance?

In addition to scheduling professional heat pump maintenance twice a year, there are plenty of things you can do:

  • Check your air filters every 30 days and clean/replace them as necessary. Never wait more than 90 days to replace your air filter.
  • Periodically check your outdoor heat pump (every 30 days) to make sure there is nothing blocking the flow of air. Remove large pieces of debris, grass clippings, and trim back any encroaching plants. Maintain a minimum 2-foot clearance around the entire unit. Make sure there is nothing stacked on top of the unit.
  • Open up all vents and registers in the home and make sure there is nothing blocking them. Open, unobstructed vents and registers are necessary for proper airflow.
  • Reduce strain on your unit by improving insulation and sealing up holes, gaps, and cracks in the home. Learn air sealing and insulation Also, remember to clean and seal your air ducts.
  1. How is heat pump energy efficiency measured?

Since heat pumps function as both heaters and coolers, their efficiency is measured by two different energy ratings—one for cooling and one for heating.

To find out the cooling efficiency of your heat pump, look for the SEER (Seasonal Energy Efficiency Ratio), normally located on the manufacturer’s label. The higher the SEER number, the more energy-efficient it is.

If you have a heat pump, you should see a second energy efficiency rating, HSPF (Heating Seasonal Performance Factor). The higher the HSPF number, the more efficient the heating portion of the heat pump is.

Learn more about energy efficiency ratings and HVAC systems.

  1. When should I replace my heat pump?

Consider replacing your unit after around 10 years. Air conditioners and heat pumps last around 10-20 years. While a well-maintained heat pump can last around 20 years, when the unit hits the 10-year mark, problems start to develop. At 10 years, your system is already past its midway point. As your HVAC system ages, efficiency drops, utility costs rise, and indoor air quality worsens.

In addition to age, you will also want to consider repair and maintenance costs on the unit. Many people follow the 50% rule, which states that if your repair costs 50% or more of the cost of a brand new system, a new system makes more sense than to dump more cash into your heat pump money pit. Learn more about whether you should repair or replace your air conditioner/heat pump.

Installing or replacing a heat pump, air conditioner, or furnace is a big decision. Learn everything you need to know before making an HVAC purchase decision.

Related Posts:


Is It Time to Buy a Central Air Conditioning System?

Why You Should Clean Heat Pump Condenser Coils

Common Winter Heat Pump Problems | Frozen Coils and More

How Zoned HVAC Improves Comfort and Gets Rid of Cold Spots

How Air Source Heat Pumps Work & Their Benefits

Heat Pump or Furnace? Or Both? | Hybrid Heating Systems

Is a Heat Pump Right for My Home?

For more information on heat pumps and other HVAC systems, contact Pacific Air Systems Heating & Cooling at (253) 292-3995 for 24/7 service.

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor.

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