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How Do Heat Pumps Work?

Heat pumps and particularly heat pump hot water systems are an Australian invention that has been on the market since the 1980’s, and are one of the most economical water heaters available.

But how do they work?

How Heat Pumps Work (Short Version)

Heat pumps operate using compressors, evaporators, and heat exchangers, and work on the principle of a refrigeration circuit–drawing heat out of one space and discharging it into another. This principle is the same as the one that powers your refrigerator, air conditioner, or reverse cycle air conditioner (also known as a heat pump).

Heat is collected from one space, and released into another. In the case of your refrigerator, the heat inside the fridge is collected, and moved into the kitchen. In the case of your air conditioner, the heat is extracted from your room, and pumped to the outside of your home. When your reverse-cycle air conditioner is working in winter, it is extracting the heat from the ambient air outside, and pumping it into the house.

That’s what a heat pump water heater does. It takes the heat from the ambient air, and uses it to heat your hot water.

Here’s the counter-intuitive part. Even below freezing, there’s still plenty of heat available. You actually have to go down to minus 273.15C to reach absolute zero, where there is no heat. So it would have to be REALLLY cold for your heat pump not to be able to work. 😉

Long Version

If you’re interested in the complete details of how heat pump hot water systems work, here’s the full rundown:

  1. The evaporator absorbs whatever heat energy is available to it from the atmosphere (air) to vaporise the refrigerant.
  2. The vapour is then compressed raising its pressure and temperature. This high temperature vapour is passed through special pipes permanently bonded around the outside of the water storage tank, forming the condenser.
  3. As the refrigerant vapour condenses back to its liquid form, it gives off its heat to the stored water.
  4. When this happens, the condensed refrigerant liquid passes back to the evaporator panels through an expansion device (TX Valve), where it is once again vaporised, and the cycle is then repeated.

The refrigerant material (usually R134a) is unusual in that it has a very low boiling (or vaporising) point of minus 26°C at atmospheric pressure, and a freezing point more than 100°C below zero. It is liquid when cold but easily becomes a vapour when heated and vice versa. It is not a CFC, and does not damage the ozone layer.

Is It Really Warm Enough for Room Temperature To Vaporise the Refrigerant?

The subject of heat and cold is really a question of relativity. People think of hot and cold relative to themselves – their comfort levels. As our normal body temperature is 36°C, an ambient temperature of +40°C is called hot, while an ambient temperature of only +5°C is said to be very cold. It is all relative.

In operation within the heat pump however, the refrigerant can be vaporising at a temperature of around minus 26°C. So an ambient temperature of +5°C is HOT compared with such a low figure.

Do Heat Pumps Need Sunlight to Work?

Because heat pumps use ambient air temperature, they don’t rely on direct sunlight for their operation. Due to their advanced design the units will produce hot water in all weather conditions, even at night. Just a simple matter of absorbing heat energy from the environment.

Thus most of today’s heat pumps can operate whether sunlight or no, in all seasons of the year, making hot water very efficiently.

What Are The Advantages Of Installing a Heat Pump Hot Water System?

Heat pumps can be used to provide hot water for domestic, commercial, industrial, swimming pool and space heating purposes. This revolutionary piece of technology is being adopted by more and more homes and businesses each year.

Here’s a quick look at some of the most compelling benefits:

Save Money In Rebates

Both the Federal Government of Australia, and a number of State Governments, recognise the efficiency of the heat pump heaters, and provide rebates and financial incentives to support your purchase.

Basically, if it’s a new installation, or replacing an electric system, you’re in business. Australia-wide, the Federal Government REC’s (Renewable Energy Certificates) will subsidise your purchase. In some State jurisdictions, there is a further subsidy available.

Save Money in Operating Costs (up to 75%)

Heating water is also the leading contributor to your home energy bill. By installing a heat pump you can enjoy up to a 75% reduction in your hot water running costs. For most families this means that the initial cost (if any) is paid back in savings within just a couple years.

Save Energy and Reduce Your Carbon Footprint

Heat pumps absorb energy from a renewable and free energy source (ambient air temperature), so only minimal amounts of electricity are required to operate. Because heating water is the largest source of greenhouse gas emissions in the home, this helps to reduce your carbon footprint and reduce global warming.

Some experts estimate that compared with a standard electric hot water system, heat pump hot water systems will save the verge family 4 tonnes or more of greenhouse gas emissions from your home.

The COP (Coefficient of Performance) of a heat pump can be over 300%! This is compared to an average electric hot water system’s COP of less than 100%. What this really means is that heat pumps consume much less energy to achieve the same output of power.

No Sunlight Required to Operate

Unlike solar hot water systems, heat pump systems do not require direct sunlight in order to operate. Due to their design, heat pump systems will produce hot water in all weather conditions, from -10°C up to 40°C, even at night. It simply absorbs heat energy from the environment – from thin air!

Easy Installation

As easy to install as a conventional electric system. There is no need for complicated or expensive “special plumbing” work to be carried out. There’s nothing to go on the roof. If you’re replacing an existing electric hot water system, the connections are the same. No solar panels are required (as opposed to solar hot water systems). The unit is installed at ground level, thereby not imposing any large additional weight on the roof. Units can be installed in less than two hours!