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BANGKOK 24 May 2019 19:49
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Payback period for inverter aircon

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Anyone know how long the payback period is for an inverter aircon unit (a type which allegedly costs a lot less to run) versus a conventional unit?

 

I'm thinking of replacing the 8 year old unit in my sitting room which is 37 m² with the aircon running perhaps 8 hours/day.

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All depends on how long you run it....if you run it 24/7 then payback will probably be in around 15 months.  Of course other factors can apply like ensuring you get a properly sized inverter A/C....if it undersized it will simply run full bore all the time like a standard A/C....you will not save anything.  

 

The 15 months perioid was the pay back period for the 23K BTU Mitsubitshi inverter A/C I bought to replace a standard 18K BTU A/C which ran 24/7.

 

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And before you buy check if you need to press a button on the remote to get the electricity savings.

 

The LG remote has a button right side, 3 buttons up from the bottom, it's marked 'SAVING'.

 

After switch on if you press the SAVING button it cuts electricity usage quite a lot. Have to do this every time you start the A/C, not difficult.

 

How this works on other brands I don't know.

 

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6 hours ago, Delight said:

What happens is that the compressor alters it speed to suit demand -but never switches off and thus never starts during its total opertating cycle-except at the beginning.

Mine does, or at least the fan stops going round and it makes no noise which I suppose means that it's off.

 

As for the pay-back period, mine paid for itself in just over a year but I'm not sure how much of the saving was down to the new one being an inverter or just being new. Certainly the old one was very old and didnt work very well, so the saving could have been greater for that reason.

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3 hours ago, KittenKong said:

Mine does, or at least the fan stops going round and it makes no noise which I suppose means that it's off.

 

 

 The invertor process refers to the compressor not the fan on the air blast heat exchanger

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9 minutes ago, Delight said:

 The invertor process refers to the compressor not the fan on the air blast heat exchanger

I know. But a compressor that is working at all would be likely to make some sort of noise I think.

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1 hour ago, KittenKong said:

I know. But a compressor that is working at all would be likely to make some sort of noise I think.

 Fans make noise due to the movement of the air.

The compressor on a  system is located outside -so not heard inside.

Outside is the 2nd air blast system -that you will hear.

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I run one invertor and one non invertor in two rooms almost identical size and for an identical time and the savings if any are minimal...

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On my Mitsubishi inverter A/C the outdoor unit is very quiet.  During cooler parts of the year when I'm still using the A/C for some cooling the outside unit will often be totally silent and the fan is not running.  Other times you can see the outside fan turning slowly (even the fan is variable speed) but you can still not hear any compressor running when standing directly under it....it's about 3 meters up on the house outside wall.  

 

Now, when it's hot you can hear the compressor run and the fan will be running faster.  

 

While I know the basic technology behind an inverter A/C is that the compressor acts a variable speed compressor based on my googling I think the compressor will actually cut off "when the cooling requirement drops below its minimum cooling capacity."  Similar to an inverter water pump that is only running at a variable speed when water is being drawn....when no water is being drawn the pump will completely turn off.

 

The particular inverter A/C I'm talking about is a Mitsubitshi inverter model number MSY-GN24VF with a "nominal" cooling capacity of 22,519 BTU but since it's an inverter A/C it's cooling capacity actually ranges from 5,118 BTU to 24,566 BTU.   When the cooling requirement drops below 5,118 BTU that is when I think the compressor cuts off completely.

 

image.png.86af7d12eb7588629e6c28f88373023a.png

 

 

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18 minutes ago, tlandtday said:

I run one invertor and one non invertor in two rooms almost identical size and for an identical time and the savings if any are minimal...

I expect the inverter is undersized for the room which causes it to run at upper capacity most/all of the time resulting in no electricity savings over a standard A/C of same size.   When that occurs your inverter A/C is nothing more than a standard fixed speed A/C.

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On 4/19/2019 at 9:25 PM, scorecard said:

After switch on if you press the SAVING button it cuts electricity usage quite a lot. Have to do this every time you start the A/C, not difficult.

Every "saving" control I have had changes the temperature settings, meaning it increases the temp you have previously set, I can't consider this as a genuine "saving"

Maybe LG is different - but I doubt it?

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I like my condo to be suitable for polar bears and had an electric bill to match (~6,000/month). Changed compressor to an inverter and my electric bill dropped to 3500. Paid for itself in about 16 months.

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48 minutes ago, Delight said:

Fans make noise due to the movement of the air.

The compressor on a  system is located outside -so not heard inside.

Outside is the 2nd air blast system -that you will hear.

I am talking about outside.

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34 minutes ago, Pib said:

On my Mitsubishi inverter A/C the outdoor unit is very quiet.  During cooler parts of the year when I'm still using the A/C for some cooling the outside unit will often be totally silent and the fan is not running.  Other times you can see the outside fan turning slowly (even the fan is variable speed) but you can still not hear any compressor running when standing directly under it....it's about 3 meters up on the house outside wall.  

 

Now, when it's hot you can hear the compressor run and the fan will be running faster.  

 

While I know the basic technology behind an inverter A/C is that the compressor acts a variable speed compressor based on my googling I think the compressor will actually cut off "when the cooling requirement drops below its minimum cooling capacity."

That is exactly my experience of my air-con. If the outside is running all the time, then at the lowest speed it is 100% silent and causes no vibration at all. That seems unlikely to me. I can certainly tell when it is running full speed and also when it is running at reduced speed as both are very audible to me. When it appears to be off it is completely silent though.

So it still seems to me that my outdoor unit turns itself off completely from time to time when demand is minimal. This mostly seems to be in what passes for winter here.

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