All About Heat Pumps
To those who haven’t been introduced to the science of heat transfer the idea that one appliance could both heat and cool their home more efficiently than separate dedicated appliances makes no sense. This is exactly what heat pump systems do, though.
What are heat pump systems?
In physics, heat pump is the technical term for the principle that common air conditioners work on. In simple language, a it is a device that actively moves heat energy from one place to another. Since heat pumps simply transfer heat around, they don’t use as much energy as conventional heaters that need to generate heat.
Air conditioners are a kind of heat pump. They transfer heat by moving refrigerant, a special liquid with a very low boiling point, through a loop of piping that goes between the indoor unit and the outdoor unit (or the indoor section and the outdoor section of a window unit). Basically, when refrigerant enters the indoor unit, it absorbs heat from the room and boils into a gas. It then travels through the piping to the outdoor unit where the compressor compresses it back into a liquid. The liquid dissipates its heat through the radiator on the outdoor unit and it makes its way back in to do it all over again.
When you run this cycle in reverse, you have the refrigerant absorbing what little heat there is outdoors on a cold, winter’s day and then releasing it indoors.
Do you really save money?
Heat pumps are twice as energy-efficient as conventional heating element-based heaters. Compared to gas and oil furnaces, though, they don’t save much money. You need to consider the fact, though, that you can also save by not having to buy a separate air conditioner for summer.
Regular residential heat pumps are only able to operate efficiently at moderately low temperatures – to around 3°C. If your area gets far colder than this, a regular heat pump will be too inefficient to move a significant quantity of heat indoors. For such needs, you need a special model called an all-climate heat pump that is 60% more efficient than a regular model.
These systems are basically reversible air conditioners. They tend to be as low-maintenance, too. If you have a well-installed system from a reputable manufacturer, your unit will typically need nothing more than a bit of periodic cleaning. The installation itself should last at least 10 years. After this, these appliances may need parts and service – both of which could be difficult to obtain, given that manufacturers usually don’t stock parts for very old appliances.
Heat pumps do have downsides
Heating your home in this way rather than with a conventional heater or furnace can feel different. Thay only produce a constant draft of warm air at around 35°C. They don’t produce air that is heated to 65°C, the way conventional heaters do. If the winter temperature in your area doesn’t go below freezing, they can heat your home adequately.
Heat pumps have a peculiar requirement – they need to shut down for 10 minutes or so once or twice every hour for a defrosting cycle. This happens in regions where winter temperatures go down to 0°C. Since the outdoor unit pumps out very cold air, it can begin to form ice before long. They then need to shut down to defrost themselves. Heat pumps made for regions that get close to freezing, then, usually have inbuilt conventional heaters to take over during defrost cycles.
Other kinds of heat pump exist
Regular heat pumps that heat and cool homes use the air-to-air principle. If you’re willing to spend a bit more, you can choose a ground-to-air model. In this type, the outdoor unit obtains the heat it needs to transfer into your home from an underground water source under your home. These are more efficient than regular air-to-air models.
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(price as of May 28, 2016)