As Melbournians head into the colder months, thoughts turn to staying warm. What’s the best reverse cycle heating system for you? Rapid Cold Air Conditioning discusses the options, their pros and their cons.
In this article we will be focusing on what are arguably the two most popular energy-efficient heating options. Reverse cycle split systems and reverse cycle ducted. Both have advantages and disadvantages, and both suit some people, house designs and climates better than others. So, which is best?
No to Gas
Firstly, we should note that we are not considering gas heating. Gas is a fossil fuel and there is simply no way to run gas appliances without greenhouse gas emissions. However, while electricity is in part generated by coal and other fossil fuels, it doesn’t have to be. You can purchase 100% GreenPower or install solar to cover your needs throughout the year and effectively be greenhouse neutral.
The economics of gas heating also no longer stack up in almost all cases. See Renew’s latest research report on this subject.
The Australian Government is now taking serious action against gas ducted heating. Regulations for supply and installation has changed as of April 2019 enforcing stricter practices to avoid carbon monoxide poisoning, read our article here. One way of avoiding such a deadly event is to upgrade to reverse cycle.
Now that is out of the way, what are the reverse cycle heating options available?
What are Reverse Cycle Air Conditioners?
Reverse cycle air conditioners work by compressing refrigerant which then transfers heat from one place to another. The technology that does this is called a heat pump. Heat pumps are all around us; for example, in your fridge, a heat pump transfers heat from inside the cabinet to outside. Which is why the outside of the fridge gets warm. In a reverse cycle air conditioner, the transfer can go either way, hence the name. In winter, heat is taken from outside and dumped inside, and in summer the opposite occurs.
A Big Pro for Heat Pumps is Efficiency
The amazing thing about reverse cycle air conditioners is how efficient they can be. For instance, electric heating using resistive elements to turn the electricity into heat can only ever be 100% efficient, however the heat pumps used in reverse cycle air conditioners are much more than 100% efficient. In fact, up to 600% efficient, meaning that they use a lot less energy to produce the same amount of heat. How can that be?
As its name suggests, a heat pump pumps heat from one place to another. Instead of turning energy from one form (electricity) into another (heat), it uses electric energy to move heat from one place to another. Because heat is relatively easy to collect and move, heat pumps can move a lot more heat energy than the electric energy they use. Plus, reverse cycle air conditioners can use a range of indoor units to suit each application (multi-head split system).
Split system vs Multi-head vs Ducted
Split systems have the compressor and one set of refrigerant coils in a box outside, often mounted against a wall. The part inside the home is called the wall hung, or head, unit and consists of the other set of coils, a fan to force air over them and the electronic controls for the system. Multi-head units are a variant, with a single (larger) compressor sized to run multiple indoor units. The outdoor unit and indoor units are linked by flexible or rigid high-pressure hoses or pipes.
Ducted systems have one (or sometimes more) large indoor units that can cover a whole house, with air being ducted to different rooms via insulated ducts. The compressor is still separate but is much larger than the units used for split systems. In some cases it may be integrated into the indoor unit.
Splits are generally the most efficient option. However, a potential disadvantage with the single split system approach is that you need an outdoor compressor for every room you want to heat/cool. This can mean many outdoor units for large homes with many rooms, which can be aesthetically unappealing and take up a lot of outdoor space. Therefore, multi-head and ducted systems get around this problem by having one outdoor unit branched off to various rooms in the house you want heat or cooled.
Zoning and Individual Control
Another advantage with split systems (single and multi-head) is zoning, as you’re only heating the rooms or areas occupied at the time. With smaller individual split systems you have complete control over which ones are running, and you can even select different temperatures for different rooms—great if one occupant feels the cold more than another.
Nonetheless, ducted systems can come with zoning. In the simplest systems, you can simply close off vents you don’t want running. However, in more advanced systems individual control can be installed to condition each room at the touch of a button. Have a look how that could work in your home by reading our zoning article here.
Another advantage with split systems is that you can start small. For instance, begin by heating just one or two rooms, and add more units as budget permits. With a ducted system, it’s all or nothing, with a larger upfront cost.
But will Reverse Cycle Heating keep me warm?
A question by people who are considering the shift to reverse cycle is whether it will keep them as warm as gas heating. The biggest perceived negatives for using reverse cycle heating for winter is whether the movement of air has a cooling effect, reducing the effective comfort of the heater.
Many manufacturers have addressed this issue with wider and/or multiple air outlets with lower air velocities and directional outlets which allow airflow to flow down along walls and floor or across the ceiling (for cooling—some manufacturers refer to as the Coanda effect, which describes how airflow attaches itself to a surface and flows along it, even if that surface curves away from the airflow).
A minimally restricted path will allow airflows to reach further across a room, more effectively distributing warm (or cool) air. By reducing airflows directly onto occupants by flowing air along surfaces, the cooling effect of moving air when heating is reduced. By selecting the correct indoor unit and location for it, you can reduce cold spots or effects. This is why it is important to arrange a free onsite measure and quote with an expert from Rapid Cold. We will take each room into consideration when choosing and correctly installing the right reverse cycle heating system for you.