Conversion to Inverter AC - What brand and does it make sense?

[Thomas J]

I have an AC which is a Carrier which is about 15 years old.  It is a 30,000 BTU unit which I think is much larger than it needed to be.  Attached is a diagram of the room areas.  It is a combined Kitchen and Living Room.  Each of those areas is approximately 16 square meters.  The AC Wall unit sits in the wall as shown in the living room.  It truly is the area that the aC is important in given that little time is really spent in the kitchen/dining area.  There is no wall that separates the two areas only a bar seating area so the kitchen gets it AC from the wall unit in the living room.  

1. Currently spend approximately 5,500 baht per month on electricity.  The living room AC runs about 12 hours per day.  The only other AC that runs is a modern inverter unit in the bedroom that runs 8 - 9 hours per night.  

2. Is it worth converting in terms of electric savings to an inverter model?  There is nothing wrong with the current Carrier unit other than it blows so cold with the 30,000 BTU's that we have to periodically shut it off and that it is modestly loud. 

 

3. Given the room configuration I think 30,000 BTU is overkill.  What size would be suggested? 

4.  Every store seems to recommend  Mitsubishi Heavy Duty.  I am not sure if that is because it is the most expensive, it really is that good, or the salespeople get a higher commission on Mitsubishi products.  What are your thoughts on a good brand(s) 

 

[Aforek]

I have  a Daikin inverter for my computer room , because many people here told it is a very good brand ; yes, good, 3 years now, no problem and electricity bill is low and it's silent ! 

 

 computer room, 10 square meters , 8.5000 BTU, 28 C degrees  ( normal temperature is 40 Celcius ) 

[sometimewoodworker]

2 hours ago, Thomas J said:

I have an AC which is a Carrier which is about 15 years old.  It is a 30,000 BTU unit which I think is much larger than it needed to be.  Attached is a diagram of the room areas.  It is a combined Kitchen and Living Room.  Each of those areas is approximately 16 square meters.  The AC Wall unit sits in the wall as shown in the living room.  It truly is the area that the aC is important in given that little time is really spent in the kitchen/dining area.  There is no wall that separates the two areas only a bar seating area so the kitchen gets it AC from the wall unit in the living room.  

1. Currently spend approximately 5,500 baht per month on electricity.  The living room AC runs about 12 hours per day.  The only other AC that runs is a modern inverter unit in the bedroom that runs 8 - 9 hours per night.  

2. Is it worth converting in terms of electric savings to an inverter model?  There is nothing wrong with the current Carrier unit other than it blows so cold with the 30,000 BTU's that we have to periodically shut it off and that it is modestly loud. 

 

3. Given the room configuration I think 30,000 BTU is overkill.  What size would be suggested? 

4.  Every store seems to recommend  Mitsubishi Heavy Duty.  I am not sure if that is because it is the most expensive, it really is that good, or the salespeople get a higher commission on Mitsubishi products.  What are your thoughts on a good brand(s) 

 

In my 16sq metre bedroom I have a 9,000 BTU unit it is a Mitsubishi, not a Mitsubishi Heavy Duty unit, it is a heat pump unit and has a setting that makes it virtually silent.

 

your 30,000 BTU is rather oversized specially if it’s not an inverter unit and will have trouble in lowering the humidity.

[Crossy]

The conventional Thai guesstimate for A/C sizing is between 600 and 700 BTU per square metre, so that would put your A/C requirements between 19,200 and 22,400 so I would be looking in that range.

 

We have an Hitachi 22,000 BTU inverter unit in our lounge which is a similar size to your space which perfoms well and the indoor unit is small compared to some others, 45k Baht installed from HomePro 

https://www.homepro.co.th/p/1145848

This 18,000 BTU unit would likely be just fine with the space you have (assuming it's not got exposed south-facing walls / windows) and is somewhat cheaper

https://www.homepro.co.th/p/1145847

 

We have Hitachi conventional units in the spare bedrooms and a Samsung conventional in our main bedroom. All have performed flawlessly although I think I'll replace the Samsung with another Hitachi inverter and move it into my workshop. 

[Oldie]

42 minutes ago, Crossy said:

The conventional Thai guesstimate for A/C sizing is between 600 and 700 BTU per square metre, so that would put your A/C requirements between 19,200 and 22,400 so I would be looking in that range.

 

We have an Hitachi 22,000 BTU inverter unit in our lounge which is a similar size to your space which perfoms well and the indoor unit is small compared to some others, 45k Baht installed from HomePro 

https://www.homepro.co.th/p/1145848

This 18,000 BTU unit would likely be just fine with the space you have (assuming it's not got exposed south-facing walls / windows) and is somewhat cheaper

https://www.homepro.co.th/p/1145847

 

We have Hitachi conventional units in the spare bedrooms and a Samsung conventional in our main bedroom. All have performed flawlessly although I think I'll replace the Samsung with another Hitachi inverter and move it into my workshop. 

Since you have inverter and conventional aircons a question. Are the inverters good in removing the humidity or are conventional aircons better? 

[Crossy]

1 hour ago, Oldie said:

Since you have inverter and conventional aircons a question. Are the inverters good in removing the humidity or are conventional aircons better? 

 

I have no scientific figures or real personal experience as I don't monitor our humidity levels. Both rooms feel equally comfortable.

 

But, IMHO.

 

An inverter should be slightly better at drying the air as it will circulate more of the room air whilst providing just enough cooling to maintain the temperature. A correctly sized conventional unit would likely be nearly as good but it's 30% compressor on/off cycle would mean that >60% of the air being circulated through the indoor unit would miss out on being dried (when the compressor isn't running). Both would have a "dry" mode anyway.

 

This issue is that a seriously over-sized conventional unit will cool the room too rapidly for it to have time to remove the moisture (the air has to pass through the unit to get dried) and will lead to that horrible "clammy" feeling. An inverter, even if horribly over-sized, would reduce it's cooling to a level that maintains the room temperature whilst continuing to dry the air passing through the indoor unit.

 

 

[sometimewoodworker]

4 hours ago, Oldie said:

Since you have inverter and conventional aircons a question. Are the inverters good in removing the humidity or are conventional aircons better? 

An undersized conventional unit will be best at removing moisture as it will run virtually nonstop, I found that about 550 BTU/square metre conventional AC  was enough in our old uninsulated bedroom.

 

now we have a slightly larger inverter heat pump unit, so in a month or so it’s going to be warming the room.

[Oldie]

Thank you both for your answer in respect of humidity. I always have the fear that if an inverter switches lower it still will cool but not reach or get below the dew point. Then it cools but without reducing the humidity. A conventional aircon will most likely always go below the dew point at least as long as the compressor runs. The heat exchanger of my inside unit goes down then to about 8 degrees Celsius what is well below the dew point. But if the compressor pauses humidity is blown back into the room because the heat exchanger is still wet. I know the dry mode. At mine the fan inside runs then only if the compressor runs too. So the inside fan only runs if the heat exchanger is below the dew point. 

 

I want to buy new aircons. Humid air at whatever temperature is a nightmare for me. So I don't know if I should risk to buy an inverter. I need 3 of them. Perhaps I try 1 inverter first. 

[Oldie]

New self cleaning technologies - do they really work?

 

This video below of the Haier technology looks impressive. First it freezes the heat exchanger of the inside unit. Then it freezes the heat exchanger of the outside unit and increases the temperature of the inside unit to about 60 degrees Celsius to have at least some desinfection. It is  for sure not hot enough for a full desinfection. Does all this bring something or is this only a kind of new marketing gag? 

 

Here the Haier video on YouTube 

 

 

 

[bankruatsteve]

10 minutes ago, Oldie said:

I always have the fear that if an inverter switches lower it still will cool but not reach or get below the dew point.

There is no dew point when using AC because it is dehumidifying.  When cool outside but still high humidity, I use the "Dry" setting which keeps RH at about 40% give or take.

[Oldie]

6 minutes ago, bankruatsteve said:

There is no dew point when using AC because it is dehumidifying.  When cool outside but still high humidity, I use the "Dry" setting which keeps RH at about 40% give or take.

There is a dew point on the surface of the inside heat exchanger. This is the reason why it can take out the moisture of the air. The moisture will condense there.

[spidermike007]

The newer technology tends to be quieter and inverters definitely use alot less electric. It is all I will buy now, for AC units, or refrigerators. 

 

I recently bought a Panasonic inverter for my bedroom, and am super happy with it. It was a bit more than some others, but worth it. Whisper quiet. Very efficient. Also have a Daikin. Very good units. 

 

And I have an Samsung 18,000 btu in my living room. Bought it almost 13 years ago. Have it thoroughly cleaned every 6 months. It was an early generation inverter. Still works great. Also very efficient. 

Edited October 27, 2020 by spidermike007

[sometimewoodworker]

32 minutes ago, bankruatsteve said:

There is no dew point when using AC because it is dehumidifying.  When cool outside but still high humidity, I use the "Dry" setting which keeps RH at about 40% give or take.

Basic physics. There is always dew point if there is any moisture in the air

You can get air with zero or virtually zero humidity, as every scuba instructor can tell you.

You will be drinking a lot of water if you breathe that for a prolonged period.

Edited October 27, 2020 by sometimewoodworker

[Mattd]

16 hours ago, Thomas J said:

1. Currently spend approximately 5,500 baht per month on electricity.  The living room AC runs about 12 hours per day.  The only other AC that runs is a modern inverter unit in the bedroom that runs 8 - 9 hours per night.  

I recently replaced 2 x 9 year old LG units in 2 bedrooms, one at 9,000 & the other 18,000 BTU with Carrier Inverter units of the same capacity, so far the electricity bill has dropped by an average of 2,000 THB per month, so in 20 months they are paid for.

[bankruatsteve]

45 minutes ago, sometimewoodworker said:

Basic physics. There is always dew point if there is any moisture in the air

Right.  Maybe I should have said the dew point is not a concern for an inverter since the compressor is running (almost) all the time.  If it is dehumidifying then it is condensing water vapor.  If it is not, then the RH is low enough that dehumidifying is not needed.