A/C Sizing Chart

Air conditioning, fans, and anything related to keeping it cool, such as insulation. This would include any posts generally discussing how to keep it cool, such as which types of blocks are better insulators.... ideal wall thickness for keeping an A/C house cool, etc.

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A/C Sizing Chart

Postby Shastadad » Thu Apr 05, 2012 9:11 am

Can anyone direct me to a chart that will "recommend" the correct size for non inverter- split type - air conditioning unit based upon the size of the room to be cooled

I have contacted Daikin, Thailand and they tell me that they cannot give me a chart but that I should check with local dealers for recommendations

Sorry, but I can't trust my local dealer to recommend a correct sized unit since the higher the BTU rating the more profit he makes from the sale

The closest that I can come to a reliable chart can be found here, unfortunately it is from the US Energy Star web site and I don't know how reliable / appropriate it would be for Thailand

http://www.energystar.gov/index.cfm?c=r ... erly_sized
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Re: A/C Sizing Chart

Postby fredlk » Thu Apr 05, 2012 9:19 am

Shastadad wrote:Can anyone direct me to a chart that will "recommend" the correct size for non inverter- split type - air conditioning unit based upon the size of the room to be cooled

I used a couple I found via Google like http://www.easycalculation.com/weather/ac.php and for my rooms 3 by 4 metres in size with ceilings at over 3 metres and well-insulated, it gave me a unit needed of 5,500 BTU but on sale here are only units of 9,000 BTU and up. My guess is that with 12,000 BTU each of your rooms would be covered although 9,000 might be large enough for your bedrooms.
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Re: A/C Sizing Chart

Postby thailazer » Thu Apr 05, 2012 9:21 am

Here is another good calculator, but you will have to guess on the climate city to use!

http://www.fairair.com.au/Calculator.Size.aspx
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Re: A/C Sizing Chart

Postby jazzman » Thu Apr 05, 2012 11:32 am

9,000 BTU is the smallest split unit aircon I know of here in Thailand. I regularly calculate aircon requirements and I find that dealers will always try to sell something bigger than what is actually needed - even if you try to convince them you already know what you need.

We avoid specialised dealers and simply source our air units from the big supermarket chains, Macro, building supplies mega-markets such as Global House, HomeMart, or HomePro where the section salespeople are basically shelf-stackers and fortunately know little to nothing about the products and will fetch from the store-room what you want with little fuss.

Beware of offers of free installation; installation is always built into the price, and outlets that do not offer 'free' installation are generally offering the same models at about ฿ 2,000 less. ฿ 1,500 (in rural areas) to ฿3,000 (city areas) is what it costs to have an aircon installed, parts/labour/gas all included. Whoever does the installation, be sure to check that the unit has been correctly connected to an independent, correctly rated MCB in your consumer unit, nine times out of ten it will not be.

Think very carefully where you want the unit(s) located because there will need to be sufficient evacuation outside for the litres of condensate it will produce.

9,000 BTU is (or should be) perfectly adequate for a typical bedroom of 4 x 4, 3.5 x 4.5 etc, say, up to about 20 m2,with a ceiling height of 2.40 (a bit low) to 2.75 (standard for mid-quality houses on housing developments) if the room and/or its roof is reasonably well insulated and people do not keep opening and closing the doors/windows etc. Nevertheless, a room should NOT be hermetically sealed. Fit brush-type draught excluders to the gap at the bottom of the doors because that's where your valuable cold air will escape. The bristles on the brush will still allow the room to 'breathe' . Any serious ventilation should be higher up, because that's where the hot air (that you don't want) will escape. Air builds astonishingly different layers of temperature in a room (try it with a thermometer) so take also into account where one wants to 'feel' the ambient temperature - this will be different in bedroom where people are lying on a bed, close to the floor, in an office or living room where people are sitting, and in an area where people are likely to be standing most of the time such as, for example, in a kitchen while people are cooking.

For confirmation, we just bought a 9,000 BTU Panasonic™ for my office (4 x 4.5) last week from a 'non-installation' outlet (Global House, Khon Kaen) for ฿9,900. Installation from our village electro shop cost ฿ 1,500. The unit works perfectly and is set for 27°, and is only on when the room is occupied. Although I am one of those people who have to budget very carefully, I'm not in the slightest bit worried about any minor impact its use may have on my monthly electricity bill. I will post again when I get a bill that reflects a full month's use.
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Re: A/C Sizing Chart

Postby Shastadad » Thu Apr 05, 2012 12:03 pm

Two additional questions:

fredlk wrote:
Shastadad wrote:Can anyone direct me to a chart that will "recommend" the correct size for non inverter- split type - air conditioning unit based upon the size of the room to be cooled

I used a couple I found via Google like http://www.easycalculation.com/weather/ac.php and for my rooms 3 by 4 metres in size with ceilings at over 3 metres and well-insulated, it gave me a unit needed of 5,500 BTU but on sale here are only units of 9,000 BTU and up. My guess is that with 12,000 BTU each of your rooms would be covered although 9,000 might be large enough for your bedrooms.


AC chart.png


thailazer wrote:Here is another good calculator, but you will have to guess on the climate city to use!
http://www.fairair.com.au/Calculator.Size.aspx


My guess would be to use Perth since it appears to have weather similar to Thailand and when I run the calculator I get 5.3kW , anyone know how to calculate that figure into BTU's ?
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Re: A/C Sizing Chart

Postby jazzman » Thu Apr 05, 2012 12:39 pm

According to one calculation I just found on line, the requirement for a typical 4.5 x 4.0 bedroom (18 m2) would be exactly:
8470 BTU (2482 watts cooling power) so a 9, 000 BTU unit as I mentioned before, seems to be about right. Don't confuse the cooling power wattage with the electrical consumption wattage. Another calculator says 2.46 Kw but doesn't provide a BTU equivalent. Yet another one says 7920 BTU, and another gives 7,500 and another gives 10,508 BTU. Many sites appear to be using the same javascript, and the one that is showing a result of around around 5,000 BTU appears to be largely innacurate. Take your pick.

Conversion:
To convert from Watts to BTU: Watts multiplied by 3.412 = BTU
To convert from BTU to Watts is: BTU divided by 3.412 = Watts
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Re: A/C Sizing Chart

Postby Shastadad » Fri Apr 06, 2012 1:46 pm

Thanks jazzman at least now I know that I am not the only one that gets different figures using the various calculators that are out there

Here is one provided via email from Panasonic, which relates to their models

CS-S9NKT Room Size : 9-13 SQ.M
CS-S13NKT Room Size : 13-18 SQ.M
CS-S18NKT Room Size : 18-24 SQ.M
CS-S24NKT Room Size : 25-28 SQ.M

CS-PS9NKT Room Size : 9-13 SQ.M
CS-PS13NKT Room Size : 13-18 SQ.M
CS-PS18NKT Room Size : 18-24 SQ.M
CS-PS24NKT Room Size : 25-28 SQ.M

CS-C9NKT Room Size : 9-14 SQ.M
CS-C12NKT Room Size : 14-22 SQ.M
CS-C18NKT Room Size : 22-30 SQ.M
CS-C24NKT Room Size : 30-36 SQ.M

CS-PC9NKT Room Size : 9-14 SQ.M
CS-PC12NKT Room Size : 14-22 SQ.M
CS-PC18NKT Room Size : 22-30 SQ.M
CS-PC24NKT Room Size : 30-36 SQ.M

Panasonic chart.png
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Re: A/C Sizing Chart

Postby geordie » Fri Apr 06, 2012 8:43 pm

Interesting i have an 18 in the living room (my choice) 48 sq mtrs l shaped and it seems to work ok ?? used at mid day it will drop the room from 35 down to 28 in 20 mins then start cycling the compressor goes off then back on again as the temperature rises Thai concrete blocks so no insulation value hot out means equally hot in But the chart shows a maximum size of 24 so does that mean two units
my comments may be wrong but never deliberately
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Re: A/C Sizing Chart

Postby unclezillion » Thu May 03, 2012 7:21 pm

you also have to consider loss through windows, non insulated walls and add 5-600 btu per person. So if you will always have 4 people in the room you will need to add 2,000 btu on top of your calculations.
Most suppliers here install for free because they make their money on the wholesale/retail price of the AC units
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Re: A/C Sizing Chart

Postby jazzman » Thu May 03, 2012 8:16 pm

'Free' installation is relative.
Most suppliers do not offer 'free' installation - it will almost always be built into the price.
Most suppliers, even if they advertise free installation, will say "Ahh,sorry but your village is too far away."
Installation costs between ฿1,000 and ฿2,000 and there are no criteria. Two tiny shops in our very small amphur town, one sells washing machines, bicycles, and booze, the other installs satellite antennae and sells second hand computers. One charges ฿1,200 and the other charges ฿2,000, both irrespective of the make and model of the unit and the work takes less than an hour. Indeed, there is nothing complicated about it. If you have the tools, some copper tubing, a bottle of refrigerant gas, a pressure guage and 60 minutes spare, you could do it yourself. But indeed why bother though for only ฿1,200 to 2,000 ?

However, one needs to be aware of the quality of the work. Is the installer going to wreck the plaster on your wall when he drills though it? Will he use a spirit level to at least mount the interior unit level? Generally these minor aesthetics are not important to non-farangs. Will he use the neat preformed plastic conduit casing for the pipes, or will he just wrap the tubes in insulating material and tape? Will he use the rubber anti-vibration feet that came with the exterior unit, or does he throw them out with the packaging?

I've seen it all, including a highly 'professional' aircon from Khon Kaen who did a free installation in Chonabot last year. The home owner couldn't fathom out why his electricity kept browning out or the MCBs kept tripping. I located the problem easily enough: the 'profis' had cut corners by simply wiring the whole thing into the 1.5mm2 lighting cables in the roof space!

IN the UK they would probably have been sent to jail for it.
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Re: A/C Sizing Chart

Postby unclezillion » Fri May 04, 2012 9:02 am

jazzman wrote:'Free' installation is relative.
Most suppliers do not offer 'free' installation - it will almost always be built into the price.
Most suppliers, even if they advertise free installation, will say "Ahh,sorry but your village is too far away."
Installation costs between ฿1,000 and ฿2,000 and there are no criteria. Two tiny shops in our very small amphur town, one sells washing machines, bicycles, and booze, the other installs satellite antennae and sells second hand computers. One charges ฿1,200 and the other charges ฿2,000, both irrespective of the make and model of the unit and the work takes less than an hour. Indeed, there is nothing complicated about it. If you have the tools, some copper tubing, a bottle of refrigerant gas, a pressure guage and 60 minutes spare, you could do it yourself. But indeed why bother though for only ฿1,200 to 2,000 ?

However, one needs to be aware of the quality of the work. Is the installer going to wreck the plaster on your wall when he drills though it? Will he use a spirit level to at least mount the interior unit level? Generally these minor aesthetics are not important to non-farangs. Will he use the neat preformed plastic conduit casing for the pipes, or will he just wrap the tubes in insulating material and tape? Will he use the rubber anti-vibration feet that came with the exterior unit, or does he throw them out with the packaging?

I've seen it all, including a highly 'professional' aircon from Khon Kaen who did a free installation in Chonabot last year. The home owner couldn't fathom out why his electricity kept browning out or the MCBs kept tripping. I located the problem easily enough: the 'profis' had cut corners by simply wiring the whole thing into the 1.5mm2 lighting cables in the roof space!

IN the UK they would probably have been sent to jail for it.


You are telling us all why we should shop around if possible! I am in Bangkok and have good engineers. i could do it myself but see no point.
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Re: A/C Sizing Chart

Postby claynlr » Thu Oct 30, 2014 1:05 pm

I used the calculator Thailazer provided. It asked for a lot of info so maybe is pretty accurate. Some of the others on the web are all over the place and do not go into the detail this one did.

Here's my question: One room is 8m x 8m and it rated at 22,178 BTU. Would you guys put in 2 smaller units across the room from each other or use one large and let it blow across the room?
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Re: A/C Sizing Chart

Postby Sometimewoodworker » Thu Oct 30, 2014 1:35 pm

claynlr wrote:I used the calculator Thailazer provided. It asked for a lot of info so maybe is pretty accurate. Some of the others on the web are all over the place and do not go into the detail this one did.

Here's my question: One room is 8m x 8m and it rated at 22,178 BTU. Would you guys put in 2 smaller units across the room from each other or use one large and let it blow across the room?

Mitsubishi has a wide and long range which are designed for bigger rooms, coverage is 100 degrees wide and 12 meters long.
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Re: A/C Sizing Chart

Postby thailazer » Thu Oct 30, 2014 1:56 pm

Sometimewoodworker wrote:
claynlr wrote:I used the calculator Thailazer provided. It asked for a lot of info so maybe is pretty accurate. Some of the others on the web are all over the place and do not go into the detail this one did.

Here's my question: One room is 8m x 8m and it rated at 22,178 BTU. Would you guys put in 2 smaller units across the room from each other or use one large and let it blow across the room?

Mitsubishi has a wide and long range which are designed for bigger rooms, coverage is 100 degrees wide and 12 meters long.

For a room that size, two units makes sense. We had a large 33,000 BTU unit in a rental house years ago and the thing was way too noisy to use. Nice thing about two units is that if the weather is not too hot, you just "fire up" one unit, and another advantage is that if one dies, you still have some cooling.
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Re: A/C Sizing Chart

Postby pipoz » Thu Oct 30, 2014 5:12 pm

Hi,

I use a rule of thumb

1.Calculate the Room Area (Not the Room Volume), assuming an average 2.3 - 2.5 meter floor to ceiling height)
i.e. 4 m x 5 m = 20 m2

2. Divide the Room Area by 14 to convert to Tons needed
i.e. 20 / 14 = 1.429 (Room area/14 = Number of Tons needed)

3 Take the figure in Item 2 and multiply by 12,000 (BTU's per Ton)
i.e. 1.429 Tons x 12,000 = 17,142 BTU's = Approximate BTU's required for that room area, so you would up size a little by 15% to say a Unit of 20,000 BTU Size.

For my 4 x 4 Room (16 m2) I am using a 18,000 BTU Unit
For my 4 x 5 Room (20 m2) I am using a 24,000 BTU Unit
For my 6 x 6.5 Room (39 m2) I am using 2 x 18,000 BTU Units

I up sized more because, of my door and window opening/area sizes, the direction the windows faced (south, north etc), my high ceilings, plus I am conservative and want it very cold very quick.

In a big room such as your, 8 x 8 = 64 m2, I personally would always use two AC Units, rather than one large AC Unit, but that is just me

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