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Inverter Air Conditioners

Inverter Air conditioners

The latest generation of air conditioners are inverter air conditioners, they are more efficient and quieter than the ealier standard air conditioners. Here we explain what makes them inverter air conditioners, how they work and what benefits they can provide.

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What is an Inverter Air Conditioner?

More and more air conditioner manufacturers are offering “Inverter” air conditioners. They are the latest technology in home cooling of air conditioners and will probably become the standard as time passes.

So what is an inverter air conditioner? Put simply it is an air conditioner designed to run continuously and, instead of switching on and off as the temperature goes up and down, it keeps running but varies its rate of cooling.

Air conditioners used to get rather fed up with rooms that simply couldn't make up their minds whether to be hot or cold. It was a tedious existence. Tessa the temperature sensor would pass on a message that old misery guts wanted his room cooler. Agatha the compressor would start work, it would take a bit of doing to get some energy into the old bones but she'd rumble into action. Unfortunately she could only work at one speed – full speed and it would take time to get moving and get into her stride. Without warning that bleeding Tessa would say “That's enough, stop now”. Agatha would stop suddenly, shuddering to a halt. Then, hours, minutes or possibly only seconds later, Tessa would be on again “come on start up, I want full speed right NOW.”

This stop start existence would drive Agatha mad and her old bones would struggle to cope to say nothing of the adrenaline needed to get going. She would clatter and bang and shudder and fart into action, bits would shake loose and it would be somewhat stressful until she got into her stride.

Then one day someone decided that the hard working Agatha deserved a bit of respect. They came up with the bright idea that if Agatha could just keep pottering around all the time perhaps increasing or decreasing her work rate from time to time the same job would get done and it would be far less strain on the old bones and take far less energy. Agatha would have to learn how to be able to adjust her work output and Tessa would have to seriously change her attitude.

Standard air conditioners have a fixed speed

Standard air conditioners have a limitation in that the most important component, the compressor, is driven by an electric motor. The speed of the motor is fixed being either on or off. Starting an electric motor, particularly if you have a load on it such as a compressor, takes a lot of energy, the telltale shudder as they start tells you that they struggle until a reasonable speed is reached. Air conditioners monitor the temperature in your room and stop as the selected temperature is reached only to start again when the room warms up a bit. The constant starting and stopping strains and wears out mechanical parts.

Some people want “instant” cooling so install large air conditioners in their rooms. This can be a mistake because if the air conditioner is too effective it will be starting and stopping far more often than a smaller unit.

Power surges when standard air conditioners start

More importantly for us a surge of electrical energy is needed to get the machine moving and here in Bali with such poor electricity supply you may find the circuit breakers cut out with the additional surge of current. Perhaps you are alright with one or two air conditioners but if you have more (and many people have 5, 6 or even 7) all starting and stopping continuously it is only a matter of time before several try to start at the same time and “pop” the lights are out and you are on the tut, in the pitch dark and you can't find the paper. You know the feeling. The inevitable groan starts somewhere around your colon and works its way out of your mouth and reverberates around the little room. You stumble about vowing that next time you will remember to put the torch in a place where you WILL be able to find it.

The solution of course – increase the electrical supply and put in larger circuit breakers. WRONG - your power bills go up, your circuit breakers won't cut out when you need them to and the rest of Bali has an even larger power shortage problem.

You could pay a bit more and buy an inverter air conditioner. They don't keep starting and stopping and they start gently when you first switch them on. They depend upon a key factor - the ability to change the speed of the motor driving the compressor.

What does the Inverter mean?

Why “Inverter” ? No it isn't some magic that makes hot air fall so it can run out under the door. It is a technical rather than Potterish approach.

Your power supply is alternating current with a fixed voltage and fixed frequency. Connect an electric motor and it goes at a fixed speed which is determined by the frequency of the electricity supply - usually 50 or 60 cycles per second which gives electric motor speeds of 1,500 revs per minute or 1,800 revs per minute (don't ask, it's not important honest).

To change the speed of a motor you change the frequency of the electric current but.... You can't change the frequency of the PLN supply without authorisation from the President and after a while he would get a bit peaved receiving 847 requests a day to say nothing of the paperwork.

“Excuse me your worthiness, my room is a bit hot would you mind just bumping up the frequency a bit, there's a good chap.”
“You will need to make your request in triplicate and submit it to the House of Representatives Frequency Regulatory Department. Don't forget to include 84 black and white photographs of yourself (not smiling), the family card and KTP of your sponsor and a validated photocopy of your passport along with the appropriate fee. Your request must be registered with your local Banjar and Polisi. A rather nice man selected for having rather large hands will collect your fingerprints in the usual assertive manner. Your request will be considered in due course.”
“Oh bother!”

Some bright (but rather boring) spark had an idea.

If we convert the incoming alternating current (positive and negative) to direct current (all positive) using a rectifier then we convert it back to alternating current using an INVERTER we can use an integrated circuit to change the frequency and the voltage. We will be able to continuously adjust the speed of the motor.

I know it all sounds a bit technical and, if you are one of those really interesting people capable of emptying a pub in five seconds who understands what I am talking about, it sounds rather like running around on the spot but this is why these things are called “Inverter” air conditioners. More to the point it means we can avoid the assertive fingerprinting.

Inverter air conditioners run continuously

The upshot of all this is you have an air conditioner that runs continuously but is able to gently change its cooling effect according to changing circumstances, it is efficient, quiet and gentle on mechanical components and the PLN supply.

The more significant AC manufacturers such as Daikin, Panasonic and Mitsubishi have inverter air conditioners available here in Indonesia.

Motion sensors for even more efficiency

The Daikin models have a clever addition. A motion sensor that detects people moving in the room. This allows you to set the machine so when you are not at home it will keep the room at a warmer temperature and save energy and money. You come home. The sensor detects movement as you launch yourself off the top of the wardrobe and your ever obedient air conditioner kicks in to take away the excessive heat.

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Copyright © Phil Wilson September 2008
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