Question About Air Conditioner Power Consumption

[frenchFARANGbkk]

Hi,

I understand how inverter aircon works but i still don't know if it's worth paying more and buy inverter aircon for a single room 30 sqm ?

Also, is it really worth buying an expensive brand as Daikin or buy any and just change it when it breaks ? (and are you sure that the cheap one will break faster? It's Japanese machines, not German anyway :-) )

Thanks for advices.

[trogers]

Hi,

I understand how inverter aircon works but i still don't know if it's worth paying more and buy inverter aircon for a single room 30 sqm ?

Also, is it really worth buying an expensive brand as Daikin or buy any and just change it when it breaks ? (and are you sure that the cheap one will break faster? It's Japanese machines, not German anyway :-) )

Thanks for advices.

Just checked my tenant's (2-person occupancy) electric bill for June - less than Bt2.7k. Two bedrooms 26m2 and 16m2 using 16,000BTU and 12,000BTU respectively. Living and dining two units of 18,000BTU. Two computers on most of the time, plus 2 LCD TV, 40" and 32".

[oldgit]

Hi,

I understand how inverter aircon works but i still don't know if it's worth paying more and buy inverter aircon for a single room 30 sqm ?

Also, is it really worth buying an expensive brand as Daikin or buy any and just change it when it breaks ? (and are you sure that the cheap one will break faster? It's Japanese machines, not German anyway :-) )

Thanks for advices.

The big advantage invertors have is that the starting current is so low.Even on the largest splits,it's only 5 amps and they all work off single phase.However,before anything else,you must check your existing incoming electrical and see if you have any spareways on your fuseboard.I installed nothing but Mitsubishi splits in HSBC branches in the South of England because they were specified by the bank.You will find that some of the cheaper brands are noisy.Ceiling mounted cassette units(two or four way throw) give an even distribution of air in a living room,for example.

[Pib]

Keeping a room/area cooled down to 20-23 degrees is going to probably keep the A/C compressor running the great, great majority of the time; and the compressor is the part of the A/C that really eats the electricity. My personal experience with cooling my home here in Bangkok with wall mounted split air systems is a setting of 25-26 degrees compared to 23 degrees reduces my electric bill by approx 20%. In my particular case it reduced the bill for this time of year by 21-24% (for the May and June electric bills) and the rate/KWH has remained the same. If no one is going to be in the room semi-soon, then the split air system for that particular room is turned off...cool down again in my case doesn't take long at all. And I feel perfectly comfortable at 25-26 degrees. ***Each person's experience/results will vary.***

[trogers]

Keeping a room/area cooled down to 20-23 degrees is going to probably keep the A/C compressor running the great, great majority of the time; and the compressor is the part of the A/C that really eats the electricity. My personal experience with cooling my home here in Bangkok with wall mounted split air systems is a setting of 25-26 degrees compared to 23 degrees reduces my electric bill by approx 20%. In my particular case it reduced the bill for this time of year by 21-24% (for the May and June electric bills) and the rate/KWH has remained the same. If no one is going to be in the room semi-soon, then the split air system for that particular room is turned off...cool down again in my case doesn't take long at all. And I feel perfectly comfortable at 25-26 degrees. ***Each person's experience/results will vary.***

Unless you are from the Ukraine, Alsaka or Scan.

[frenchFARANGbkk]

Sorry, as many air con experts seem to be reading this thread, I want to ask if you know any problem with "hidden" aircons type, I mean the same as we see in hotels where the fan (indoor part) is in the ceiling, I guess the machine is the same and they just put it inside the ceiling instead of mounting the metallic box on the wall, but maybe you know any reason not to buy this kind of aircon ?

It is more expensive but it seems the only way to avoid wall mounted aircons which usually are not so design.

Thanks for any advice.

[trogers]

Sorry, as many air con experts seem to be reading this thread, I want to ask if you know any problem with "hidden" aircons type, I mean the same as we see in hotels where the fan (indoor part) is in the ceiling, I guess the machine is the same and they just put it inside the ceiling instead of mounting the metallic box on the wall, but maybe you know any reason not to buy this kind of aircon ?

It is more expensive but it seems the only way to avoid wall mounted aircons which usually are not so design.

Thanks for any advice.

Basically two kinds of 'hidden': ducted and ceiling mounted above suspended ceiling.

Cooled air that is distributed by ducts are usually large units or central air-con system.

Ceiling mounted units above suspended ceilings are commonly found in the bedrooms. Similar problems as wall types if an access service panel is provided at the ceiling. Require regular cleaning, and its cooling power for the same BTU size depends on distance to the compressor unit.

Wall types are usually promoted with extra features like advance electronic temperature control, ionic air treatment, etc.

Edited July 31, 2009 by trogers

[oldgit]

Sorry, as many air con experts seem to be reading this thread, I want to ask if you know any problem with "hidden" aircons type, I mean the same as we see in hotels where the fan (indoor part) is in the ceiling, I guess the machine is the same and they just put it inside the ceiling instead of mounting the metallic box on the wall, but maybe you know any reason not to buy this kind of aircon ?

It is more expensive but it seems the only way to avoid wall mounted aircons which usually are not so design.

Thanks for any advice.

Basically two kinds of 'hidden': ducted and ceiling mounted above suspended ceiling.

Cooled air that is distributed by ducts are usually large units or central air-con system.

Ceiling mounted units above suspended ceilings are commonly found in the bedrooms. Similar problems as wall types if an access service panel is provided at the ceiling. Require regular cleaning, and its cooling power for the same BTU size depends on distance to the compressor unit.

Wall types are usually promoted with extra features like advance electronic temperature control, ionic air treatment, etc.

Another thing to bear in mind with concealed ceiling ducted units is the total resistance of the ducted system placed on the evaporater fan.When the fan is working,it must overcome the 'index run' i.e. the distance between the fan outlet and the last grille or diffuser.It isn't,therefore,just a case of calculating the cooling requirement with this type of system.If the evaporater fan motor isn't 'man' enough,then you will have to step up to the next model or find an alternative manufacturer.

Incidently,trogers,after seeing your condo living room,did you think about installing a ceiling mounted inverter cassette unit?

[neverdie]

Hi,

I understand how inverter aircon works but i still don't know if it's worth paying more and buy inverter aircon for a single room 30 sqm ?

Also, is it really worth buying an expensive brand as Daikin or buy any and just change it when it breaks ? (and are you sure that the cheap one will break faster? It's Japanese machines, not German anyway :-) )

Thanks for advices.

Im not air con expert (drip under pressure) but I will tell you about my experience with INVERTER aircons. I've had two of them and my latest one a new Panasonic Inverter A/C is sooo cheap to run, I can barely believe it. I only have a small bedroom, just under 20 metres square with ceiling at 2.7m. The ceiling is one of those tiled jobs, with the 600x600 tile sitting inside the alloy strips, so I bought some 2 inch insulation and threw it up there to try and help.

So, the aircon, I set at 25 or 26 deg and from what I can work out by monitoring the meter and cost of it, it roughly uses 1.8 to 2 units of electricity in a 12 hour period and thats when its hot. On the cooler nights, its like the thing is running on the smell of the electrical cable. The unit cost me 34,000thb, probably could of bought a medium range one, non inverter for about 20,000thb. Anyway that all means I can cool my bedroom for about 200 baht a month. With the non inverter unit it was considerably higher.

I also have a larger unit in the other part of the house & when you fire that baby up the lights dim, its a non inverter unit.

Personally I would go for inverter units every time from now on, especially when cooling smaller areas and areas that I require to keep cool for longer periods.

[trogers]

Incidently,trogers,after seeing your condo living room,did you think about installing a ceiling mounted inverter cassette unit?

That will clash with the ceiling design. When I bought the unit, the ceiling was fixed at 2.4m from balcony to the kitchen. I demolish the old ceiling, and build a new one following the profile of the structural floor (2.9m) and beams, and then put in a border at 2.4m all round to run my pipes, conduits and exhaust ducts. Strip lighting is then added to lift the whole atmosphere.

My two wall type air-con units are fixed to a gypsum wall with pipes running in the cavity with the block wall on the other side. This double wall is to improve sound insulation between the living areas and the master bedroom, as well as provide a cavity for services.

[Bpraim1]

I run a Pano 24,000btu and a small samsung 12,000btu to cool my livin space of 96m2, Power bill has only once gone over 2000bht.

My aircon run's at 26c all day all night unless it is cooler then this outside or we're not home.

I leave my computer on most times, two fridges, two tv's, two water pumps/lift pump and presure stablizer pump. Hotwater heater.Plust he oven get's a good workout each month.

I can not say enough about good insulation.

[aussiebebe]

The ceiling is one of those tiled jobs, with the 600x600 tile sitting inside the alloy strips, so I bought some 2 inch insulation and threw it up there to try and help.

I have a similar suspended ceiling - do you just lay the insulation out? Is it a roll? Roughly how much is it per square meter?

Also, to Bpraim1,

I can not say enough about good insulation.

how would you insulate a suspended ceiling? Could you give any tips on cost-effective insulation?

[neverdie]

Aussiebebe,

Yeah I bought the stuff at homepro, it came in a roll, I think 4 metres long, 600mm wide and I was a tight asssss and only bought the stuff 2 inches thick. There is are also 4 & 6 inch thicknesses. From memory my stuff was only about 200 baht per roll. Its fibreglass insulation like the pink bats you can get in my home country, only its in a roll covered by foil, which is great because its easy to handle. I simply popped up the tiles and rolled the baby out....I used a old hose to belt it down where I couldnt reach. It looks pretty AND

Its really made a huge difference, I am now wondering what would of happened if I used 4 or even 6 inch stuff, maybe I would have to buy a heater to warm up a bit. I think the 4 inch stuff was about 350 per 4 metre roll and about 500 per roll for the 6 inch stuff.

Now when I get up in the morning, I turn off the A/C and keep the door shut, the room stays cool for hours without the A/C running. Later in the morning I open my louvre windows & the room doesnt get hot until later in the PM.

I also got a bit freaky before moving into the house and tore the internal wall apart and stuff insulation into it, just because im a freaky kind of guy. but i dont think that made much of a difference.

[Bpraim1]

I have seen some nice insulating and acoustic batt tiles that you can use in a suspened ceiling. I believe from Siam cement Group.

I used Spray foam in the walls and roof and then foil backed batt on top on the gypsum on my ceiling. I had to make small boxes around each of my downlights and cover with batt to keep a good line of insulation. And taped all the seams with foil tape.

I run a small an on a thermo switch to control the temp between the cieling and roof, though mostly to remove any moisture from this area. I will be installing a solar fan soon to preform this job.

Biggest problems is heat buildup in the daytime. Brick and cement love to soak it up along with water. Like a hard sponge!

Besides your ceiling you should look for ways to keep your walls out of the sun and good ventalation in your attic space.

Try planting some trees, cover windows with blinds and make sure windows close properly. If you are stuck for space, you could try repainting your house with a Ceranic paint, or at the least a softer colour.

Make sure your compresser is out of the sun.

Cool you house early, not when it is already hot.

[trogers]

I insulated the west wall of my mother-in-law's house by building a single Viva board layer with a 2-inch cavity over the external face of the existing brick wall. This Viva board layer starts 6 inches above the floor and is 6 inches below the roof rafters to allow the heated air cavity to ventilate freely.

Edited August 1, 2009 by trogers

[oldgit]

I insulated the west wall of my mother-in-law's house by building a single Viva board layer with a 2-inch cavity over the external face of the existing brick wall. This Viva board layer starts 6 inches above the floor and is 6 inches below the roof rafters to allow the heated air cavity to ventilate freely.

I could do with that type of insulation at my place.Where do you get the Viva board and how much does it cost? Presumably,brackets are part of the assembly.

[trogers]

I insulated the west wall of my mother-in-law's house by building a single Viva board layer with a 2-inch cavity over the external face of the existing brick wall. This Viva board layer starts 6 inches above the floor and is 6 inches below the roof rafters to allow the heated air cavity to ventilate freely.

I could do with that type of insulation at my place.Where do you get the Viva board and how much does it cost? Presumably,brackets are part of the assembly.

Any contractor who installs lightweight gypsum partitions can do it for you.

Viva boards can be exposed to the weather. I used 1"x2" timber support frames instead of metal studs.

http://www.viva.co.th/

Price if in Bangkok is about Bt700/m2 including 2 coats of paint.

Edited August 2, 2009 by trogers

[ronswelters2]

If I have a room which requires say, 36,000 BTU (by the home pro rough guide thingy) would I best off getting two smaller units or one large one?

Conventional wisdom suggests two smaller units

Better efficiency during the cooler periods (run only one).

You at least get some cooling if one unit fails.

Better distribution of cooled air around your room.

Crossy said it all

Yes, Crossy has it pretty right. The standard tables say from HomePro which seem to be taken from manufacturers recommendations call for much larger size than should be necessary, with lots of on/off cycling which fails completely to keep the air dry which is much more important than cool. A 20 deg target is ridiculous, 27 is fine for comfort if the RH is low. Most people cannot make the distinction, they just stay "cool" meaning they feel cool. The aircon control is even less smart, it's never heard of "humidity".

The whole design procedure including window facing, insulation, and everything else which is based on ASHRAE steady-state procedures is great for factories but useless for most of our needs, which are mainly for evening/sleeping times, when thermal mass and afternoon heat gain are the driving loads. Ironically, 100 percent windows and no insulation are best at these times. Nothing beats a hot tin roof at midnight because the sky temperatures are way down as low as 10 or 15 at that time.

I like the Crossy idea of starting with one unit, maybe even 9000 BTU/hr. For sleeping the best and only really sustainable solution would and will someday be a much smaller unit, maybe 3000-4000 BTU/hr cooling an enclosed sleeping space such as inside a net. With a good overhead fan, this machine would only have to be used on unusually warm/humid nights. Unfortunately nothing like that is available on the market today.

Ron Swelters

Edited August 2, 2009 by ronswelters2

[trogers]

The whole design procedure including window facing, insulation, and everything else which is based on ASHRAE steady-state procedures is great for factories but useless for most of our needs, which are mainly for evening/sleeping times, when thermal mass and afternoon heat gain are the driving loads. Ironically, 100 percent windows and no insulation are best at these times. Nothing beats a hot tin roof at midnight because the sky temperatures are way down as low as 10 or 15 at that time.

Do you reside in a house that can only be livable between sunset and sun rise?

[frenchFARANGbkk]

Hello,

Can somebody confirm that if I buy an INVERTER aircon it's better to buy 24000 btu than 18000 because the 24000 will work less "hard" as the 18000 ?

Thanks to inverter system the compressor of the 24000 btu air con will move at lower speed than the 18000 btu machine ?

Thanks.

[trogers]

Hello,

Can somebody confirm that if I buy an INVERTER aircon it's better to buy 24000 btu than 18000 because the 24000 will work less "hard" as the 18000 ?

Thanks to inverter system the compressor of the 24000 btu air con will move at lower speed than the 18000 btu machine ?

Thanks.

Buy a size that suits your room's dimensions and function of the room. Too large is a waste of capital outlay, and achieving coolness without reducing humidity. Too small and the compressor will not have much time to rest or if inverter, to run at reduced speed.

[ronswelters2]

The whole design procedure including window facing, insulation, and everything else which is based on ASHRAE steady-state procedures is great for factories but useless for most of our needs, which are mainly for evening/sleeping times, when thermal mass and afternoon heat gain are the driving loads. Ironically, 100 percent windows and no insulation are best at these times. Nothing beats a hot tin roof at midnight because the sky temperatures are way down as low as 10 or 15 at that time.

Do you reside in a house that can only be livable between sunset and sun rise?

If you are going to spend a lot of time home in the day then the design criteria have to shift in that direction. But a well-designed house inThailand should still be liveable most of the time, and especially most mornings, without aircon. I agree that on especially hot times of day or when you might want a daytime snooze aircon is ok, but only ok because aircon in Thailand either cycles on and off which is uncomfortable or if it is kept running produces cold clammy air. Aircon is in general not really good at dealing with humidity and humidity is the big problem in Thailand.

Ron

[oldgit]

The whole design procedure including window facing, insulation, and everything else which is based on ASHRAE steady-state procedures is great for factories but useless for most of our needs, which are mainly for evening/sleeping times, when thermal mass and afternoon heat gain are the driving loads. Ironically, 100 percent windows and no insulation are best at these times. Nothing beats a hot tin roof at midnight because the sky temperatures are way down as low as 10 or 15 at that time.

Do you reside in a house that can only be livable between sunset and sun rise?

If you are going to spend a lot of time home in the day then the design criteria have to shift in that direction. But a well-designed house inThailand should still be liveable most of the time, and especially most mornings, without aircon. I agree that on especially hot times of day or when you might want a daytime snooze aircon is ok, but only ok because aircon in Thailand either cycles on and off which is uncomfortable or if it is kept running produces cold clammy air. Aircon is in general not really good at dealing with humidity and humidity is the big problem in Thailand.

Ron

A standard split system (with a direct expansion coil within the indoor unit) will dehumidify a room naturally.

[Neeranam]

HomePro use a quick-and-dirty table to size your aircon, it makes a vast number of assumptions but here it is anyway

BTU - - - - - - - Sq Meters

9,000 - - - - - - 9-15

12,000 - - - - - 16-20

18,000 - - - - - 21-30

24,000 - - - - - 31-35

30,000 - - - - - 40-50

36,000 - - - - - 50-55

OR

Floor area (in square metres) X by 600 gives you the size of the aircon (in BTUs).

If you're going to want arctic conditions you'll need the next bigger unit than this table suggests.

Whatever you do, don't think 'bigger is better', a big aircon cycling slowly will not produce the drying effect that helps you feel cooler.

That's good as I'm buying a unit today but what ceiling height is that based on?

[oMega69]

Not sure i belive that HomePro scale . . . .,,

Any way . . i need to buy a A/C for a condo facing North "Pattaya" , 48sqm include the balcony. . , What BTU to use and what brand drain less energy ? . . ,

Thanks..

can trust this one ? http://www.btucalculator.net/

Edited February 24, 2010 by oMega69

[stgrhe]

Not sure i belive that HomePro scale . . . .,,

Any way . . i need to buy a A/C for a condo facing North "Pattaya" , 48sqm include the balcony. . , What BTU to use and what brand drain less energy ? . . ,

Thanks..

can trust this one ? http://www.btucalculator.net/

These crappy calculators, or Home Pro's own version too for that matter, are only giving you a very brief guideline of the cooling capacity requirements. You need to consider:

1. The volume of the space to be cooled (not the floor area).

2. The number of windows, their sizes and whether they have single, double or triple glasses.

3. The room's orientation (south, north etc.)

4. Number of people that normally occupy the room.

5. Whether there are substantial heat generating equipment in the room.

6. Ceiling/roof insulation if any.

7. Wall types (which material and with or without cavity and insulation).

8. Climate zone.

9. Average relative humidity.

10. Your target cooling temperature and relative humidity in the room.

[bailly]

Glad I am an Air Conditioning Engineer sorry had to do it

Edited April 8, 2010 by bailly

[PattayaParent]

I used to work with a HVAC engineer that could tell you the approximate BTU to be used if you told him the volume of the room.

He multiplied the volume by a factor to get the BTU.

Does anyone know what that factor is?

Edit: Obvioulsy for a confirmation of sizing other factors have to be considered but for estimating purposes the factor is close enough.

Edited April 10, 2010 by PattayaParent

[Naam]

I used to work with a HVAC engineer that could tell you the approximate BTU to be used if you told him the volume of the room.

He multiplied the volume by a factor to get the BTU. Does anyone know what that factor is?

Edit: Obvioulsy for a confirmation of sizing other factors have to be considered but for estimating purposes the factor is close enough.

that would be the equivalent of estimating the boob size of your girlfriend if you tell him which day and month she celebrates her birthday.

[WilliamCave]

Air con electricity consumption also goes up,, or the efficency level is down when they are not set up properley, Every time when we get ours cleaned or serviced the service people never put on the guages to test the preasures, the only thing they say is it is ok. Service techs in thailand are not up to speed on AC units. My new house I am relocating 5 of them and am going to put the guages on the system myself and do my own testing. And maintenance.

Or call the company that deals with 7/11 stores