The popularity of heat pumps in Beckley, WV, has skyrocketed in recent years, as they are a great alternative to traditional heating and air conditioning. A heat pump can function as an air conditioner to cool a home in the summer and also switch to provide heating during the winter. Heat pumps are without a doubt a very energy-efficient heating option, but many people remain hesitant about switching to a heat pump system out of concerns that it won’t heat effectively in cold weather. While heat pumps do have some limitations, the fact is that they can still provide effective heating unless the temperature is extremely, bitterly cold. In this guide, we’ll discuss how heat pumps work in cold weather and explain their limitations. This will help you determine if this type of unit is a good choice for your home.
How Heat Pumps Transfer Heat Energy
Most heat sources simply transform one energy source, gas or electricity, into heat. Heat pumps, on the other hand, don’t actually produce heat. Instead, they remove or absorb heat from the air outside and release it into the air indoors. This heat transfer process allows heat pumps to produce two to four times more heat energy than the amount of electricity they use. This means they are between 200 and 400% efficient. This makes them much more efficient than furnaces and other electric heating options, which are all only 80 to 100% efficient.
As the cold refrigerant flows through the coil in the heat pump and absorbs heat from the air blowing over it, the temperature increases and the refrigerant starts to boil. Before being pumped inside, the refrigerant first passes through an expansion valve. This rapidly decreases the pressure of the refrigerant, causing it to fully boil and become a superheated gas. As the hot gas moves through the coil inside the building, all of the heat is automatically released into the cooler air being drawn over the coil by the blower, so that the air temperature greatly increases. The blower then forces the hot air into the supply ducts, where it eventually flows out of the vents in each room.
Heat Pump Temperature Limitations
Modern heat pumps are much more efficient and effective than units produced even a decade or two ago. This allows them to continue heating in much colder conditions. Most new heat pumps designed for use in colder climates can work in temperatures as low as -22 degrees Fahrenheit. Air always contains some heat energy, no matter how cold it is, which means that the refrigerant flowing through the heat pump can continue to capture some heat even when the air temperature is well below freezing.
As you might expect, the amount of heat energy in the air does continue to decrease the colder the air temperature gets. This means that as the air temperature decreases, the effectiveness of the heat pump also decreases. This causes it to heat more slowly. The decreased rate of heating means that heat pumps will often need to run almost constantly in extremely cold conditions. This typically isn’t an issue when the home is already warm and the indoor temperature is at or near whatever temperature you have your thermostat set to. In this case, the heat pump will still typically be able to produce enough heat to maintain a consistent indoor temperature.
How the Auxiliary Heat Source Works in a Heat Pump System
There is an issue with the amount of heat a unit produces when the outdoor temperature is extremely cold. Typically, a heat pump will only be sufficient to raise the indoor temperature by a few degrees, even when the unit runs almost constantly. Let’s say that you have your thermostat programmed so the temperature turns down to 60 at night. The temperature is then set to go back up to 70 degrees in the morning. If the temperature outside is well below freezing, a heat pump could run constantly without ever fully bringing the temperature back up to 70 degrees. This is why all heat pump systems in cold climates must also have some type of auxiliary or backup heat source.
If the indoor temperature is more than 2 or 3 degrees colder than it should be, the thermostat won’t signal the heat pump to run. Instead, it will switch on the auxiliary heat source so that the home heats up more quickly. Once the thermostat senses that the temperature is where it should be, the system will switch back to the heat pump. It will then run as needed to maintain the correct temperature.
In most heat pump systems, the auxiliary heat source is either a furnace or some type of electric resistance heating. Many modern heat pump systems have electric-resistance heating elements that serve as an auxiliary heat source. The system will automatically turn on these heating elements whenever a lot of heat is needed. Also, whenever the outdoor temperature is too cold for the heat pump to continue working effectively, the auxiliary heat source will also be used during the defrost cycle.
Understanding Heat Pump Defrost Cycles
When a heat pump runs in colder weather, frost slowly starts to form on the coil, causing it to ice up. As the layer of ice builds, it starts to block the air flowing through the unit from reaching the coil. This prevents the refrigerant from pulling heat out of the air. This means the heat transfer process won’t work until the coil fully defrosts and all of the ice melts.
The temperature of the refrigerant flowing through the coil is always at least 10 degrees colder than the air temperature. The fact that the refrigerant is colder than the air means that frost can form on the coil even when the outdoor air temperature is above freezing. In temperatures around 40 degrees, a heat pump won’t need to defrost all that often. Ice will obviously form more quickly in colder conditions, leading to the heat pump often needing to defrost every 30 to 90 minutes. Each defrost cycle typically lasts less than 10 minutes. It can take longer when the outdoor temperature is much colder.
All heat pumps have internal sensors that detect the temperature of the coil. When the sensors detect that the coil is frozen, they will signal the defrost cycle to start. This also signals the thermostat to turn on the auxiliary heating to maintain the temperature in the home while the defrost cycle runs.
In order to defrost, a heat pump activates its reversing valve so that the refrigerant moves through the system in the opposite direction. This means that cold refrigerant flows to the indoor coil and captures heat from the warm air in the home. The heated refrigerant is then pumped through the outdoor coil so that all of the ice melts. In most cases, the defrost cycle will continue to run until the sensors detect that the coil temperature is around 55 degrees. This ensures that all of the ice is fully melted.
Childers Air Plumbing & Electric is the top choice if you’re looking to install a new heat pump, furnace, boiler, or air conditioner. We also provide professional heating and AC repair and maintenance services for customers in the Beckley area. We also offer residential electrical and plumbing services. To learn more about whether a heat pump is right for your home, give us a call today, and we’ll be happy to answer any questions you have.