How Does a Heat Pump Work?
Heat pumps move heat. It can't get any simpler than that. Think about your air conditioner. What happens when your air conditioner is running? It removes heat from your house and puts it outside. But what about the cold air it puts in the house...you ask. Your air conditioner is actually removing heat from the air. The absence of heat is cold. When your air conditioner is running, go outside and put your hand above where the fan is blowing air. This piece of equipment is known as a condenser. If you feel the air, it is warm or hot. That is heat that is coming out of your house.
So how does a heat pump heat your house? Think of a air conditioner running in reverse. Instead of removing heat from your house in the air conditioner mode, the heat pump has a reversing valve which allows it to run in reverse. In the reversed mode...the heat mode, a heat pump is moving heat from outside and putting it in your house. Wait a minute, it's 50 degrees outside. How can this be possible? There is actually heat in cold air. In fact, there is heat in cold air all the way down to "absolute zero" which is approximately "minus 460 degrees". If the outdoor temperature is in the 50 degree range, a heat pump is very efficient at extracting heat from the air. As the temperature drops, at some point (typically between 45 and 30 degrees F) the heat pump system will reach it's balance point. The balance point is the outdoor temperature point at which the heat pumps output equals the needs of the space being heated. On days where the temperature stays below the "balance point" a heat pump will utilize a supplemental heat source, which is usually an electric heating element.
An electric heating element glows red when it is functioning, just like the wires inside a toaster. If you are heating with electricity you should know that a heat pump can save you as much as 30-40% on your electric bill. That's because heat pumps don't generate heat, they move heat. Therefore heat pumps can provide up to 4 times the amount of energy they consume. The most common type of heat pump is the air-source heat pump. Another type of heat pump is a geothermal heat pump, which uses the ground or a water source to disperse heat. A geothermal heat pump is very efficient but can be costly to install.
Besides being more cost effective than electric heat there are a few other advantages to using a heat pump. Heat pumps are safer than gas furnaces because there is no gas to leak and because they do not burn fuel. They also provide a more uniform temperature. A home heated with a heat pump provides a healthier enviorment than one heated with electric heat or a gas furnace. That's because an electric air handler or traditional gas furnace dries out the air you breathe and can dry your skin.
As to the workings of a heat pump, in the air conditioner mode, air is forced through a coil inside the house or attic by a fan or blower. As the air passes through the coil, refrigerant in liquid form absorbs heat and is turned into a gas. This gas takes the heat to the outside condenser coil where it is cooled and compressed back to a liquid. The extracted heat is deposited outside. In the heat pump mode the opposite happens. Outside air passes through the condenser coil and heat is extracted and pumped into the house via the inside evaporator coil.
When an air-sourced heat pump operates in cold weather the outside coil can ice over. Even though the temperature might be at 40 degrees this coil icing can occur. That's because the air temperature on the back side of the coils can be 10 degrees cooler than the outside air because heat is being pulled from the air passing through the coils. If the coils have iced over, they must be periodically thawed for the heat pump to continue working. There are different ways to thaw the coils but the most common way believe it or not is to turn on the air conditioner and extract heat from the house to warm the coils. To keep the occupants of the house from receiving a blast of cold air the supplemental heat source is kicked on. This is usually heat strips but can be gas heat. Once the coils have thawed the defrost controls causes the reversal valve to switch back to heating mode.
In summary, if you are in a moderate climate zone and are heating with electricity, you should definitely consider a heat pump. The savings could be 30-40 percent.
Heat Pump, Repair, Installation
Heat Pump, Repair, Installation
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