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Air Conditioner Water Heaters

Using Your Air Conditioner to Heat Your water

We can heat our water at no additional cost by using an air conditioner water heater. These simple devices are not expensive to buy and use the heat that your air conditioner removes from your house to heat the water. Here we look at how they work, how efficient they are, the savings we can expect and how quickly they will pay for themselves.

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Using the heat from your air conditioner to heat your water

Air conditioner water heater

Now there is a sensible, practical and, most importantly, low cost way that most of us can heat our water.

Known as the Air Conditioner Water Heater it is a simple device that takes the heat that is normally thrown away by an air conditioner and uses it to heat water. The heater consists of an insulated water tank very similar to a standard electric water heater. Instead of a heating element the tank has a heating coil from the air conditioning system which heats the water.

Only two hours of running time of your air conditioner will heat a 100 litre tank of water to 65 degrees centigrade. Is this hot enough? Well most solar heaters work on a maximum of 60 degrees, any hotter than this is considered dangerous should an unsuspecting child turn on a hot tap.

Unlike a solar hot water heater these heaters can work both night and day. They are considerably cheaper than solar water heaters and in fact cost very little more than a standard electric water heater.

Once installed they require no energy to operate. The hot water is free. These units are available with an electric heating element should you think you might need electric heating as a back up.

How do Air Conditioner Water Heaters work?

Let us start by looking at a standard split air conditioner. An air conditioner is a heat pump, it removes heat from your house. It has a heat exchanger in a unit mounted on an internal wall of your house which collects heat. It has another heat exchanger which disposes of this heat outside your house. See the explanation here.

The key to the system is the rather clever refrigerant stuff (we often wrongly call it freon, Freon is in fact the DuPont trade name for CFC based refrigerants that are ozone depleting and banned). So what is this refrigerant stuff, is it a gas? Like other gases if you compress or remove heat from a refrigerant it will turn into a liquid.
Or is it a liquid? Like other liquids if you heat it it will boil and change into a gas by absorbing the heat.

Refrigerants are special in that they boil well below room temperature.

So in our air conditioner we have a length of pipe containing refrigerant gas. In our outdoor unit the gas is compressed to turn it into a liquid. As it changes to liquid (it unboils so to speak) it gives off heat which a fan blows away. The refrigerant liquid now moves around the system to our wall mounted indoor unit, here the pressure is released and the liquid boils evaporating back into a gas and absorbing a lot of heat from the room. A fan draws air from the room and blows it over the heat exchanger pipe so the evaporation of the refrigerant removes the heat from it. The refrigerant, now a gas, returns to the compressor unit to be compressed into a liquid again.

In the Air Conditioner Water Heater the pipe in which the gas is compressed goes through the water heater before it goes through the outdoor heat exchanger. The heat given off as the gas is compressed directly heats the water. The heat is literally pumped out of the refrigerant into the water.

How efficient is an Air Conditioner Water Heater?

This is far more efficient than a standard electric water heater in which an electric heating element converts electrical energy to produce heat. An air conditioner is a heat pump, it doesn't produce heat, it moves heat. This is why an air conditioner typically uses only a quarter of a kilowatthour of electrical power to produce a full kilowatthour of cooling in your house and, with the addition of an air conditioner water heater, a full kilowatthour of heating for your water at the same time.

Air Conditioner Water Heaters are sound technology, they are very simple, low cost and highly effective.

There is another significant advantage here in Bali. Our electrical supplies are often very unreliable and many of us suffer electrical drop outs due to power surges as high demand items such as water pumps and heaters switch on and off. An air conditioner water heater removes the high electrical consumption of an electric water heater from our systems and so can reduce our electrical problems.

How much power and money will an Air Conditioner Water Heater save?

A standard electric water heater takes about 4.2 kilowatthours of electricity to heat a 100 litre tank of water from 24 degrees centigrade to 60 degrees centigrade. A kilowatthour of electricity currently costs 1,340 Rupiah in Indonesia.

If you use a tank of hot water every day this will cost you about 2 million rupiah a year. This means that an air conditioner water heater will pay for itself in about 2.5 to 3 years - a considerably faster pay back than a solar hot water system which may take 6 to 12 years to pay for itself depending on the model you buy.

If you are, like me, a person who has learned to live in this wonderful climate without air conditioning obviously you will have to go solar.

For you frosty types that have air conditioners running there are two brands of air conditioner water heaters available in Bali, Wika and Rifan, and domestic systems come in 75 litre (one bathroom) and 100 litre (two bathroom) sizes.

These days this is safe technology, the dangerous days are gone when "Alternative" people dressed in anoraks and balaclavas held secret meetings in the back rooms of dingy pubs and whispered phrases like "The one armed striptease artist likes hers sunny side up" which of course means "I would like to buy a solar panel."

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Copyright © Phil Wilson February 2010
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