What size AC for 50 sq mts and 15 sq mts?

[FACTOR]

Hello. What size AC do I need for a 50 square meter room and another AC for a 15 square meter room? How many BTUs?

Thanks.

[Crossy]

Quick and dirty estimate:-

50m² => 30,000 BTU

15m² => 9,000 BTU

But there are many factors to take in to account, best to get your local A/C man to do a survey particularly of the big room, probably best to have two smaller units to get better cooling distribution.

[JesseFrank]

Most hardware stores will calculate 600 BTU per sqm, the technical department of Daikin company advises 800 BTU per sqm.

[FACTOR]

Crossy, Thanks.

[FACTOR]

Most hardware stores will calculate 600 BTU per sqm, the technical department of Daikin company advises 800 BTU per sqm.

Thanks for the equation. Very useful. I understand Daikin make good equipment.

[JaiLai]

Most hardware stores will calculate 600 BTU per sqm, the technical department of Daikin company advises 800 BTU per sqm.

Thanks for the equation. Very useful. I understand Daikin make good equipment.

+1 on the info, very handy for rule of thumb.

[kyrre]

It also depends on your needs..

Is it to be used at daytime..

Do you plan to have 18 degree or 24-26, or just to dry the air.

I have a 9000 BTU in a 30+sqm room and with no problem keeping it comfortable at night..(Was installed before i bought)

I will say that from 500-800 BTU /sqm can be used after what need you have.

I run only at night and have 25-27 degree and can use a undersized unit with no problem.

[Khun Jean]

I have two 9000 btu in a 48m2 and another 9000 btu in a 16m2. Tye are converter types

Works good and is able to cool it down rapidly.

[lopburi3]

As said it is easy to buy too much so highly advise the two units for the 50 square meter as you will most likely end up only using one most of the time. My ground floor bedroom with normal cement covered brick with outside roof and thin fiberglass mat and one large window is 25 square meters and has an 18k unit but when it failed decided to have a backup just in case and installed a 9k unit to allow enough for sleep hours. That was about 4 years ago and have only started the 18k unit on about 3 days for more than test since then as 9k takes care of room 24 hours a day. But I do not like freezer conditions so normally run it at 26-28 degrees - if you like meat locker feeling then it probably would not be enough.

[FACTOR]

Thanks for all the good advice. Now, I'm thinking of going for two 9000 btu units in the large -- 50 sq mt -- room. Run them separately depending on what part of the room I'm in. Makes a lot of sense.

Thanks.

[JesseFrank]

As said it is easy to buy too much so highly advise the two units for the 50 square meter as you will most likely end up only using one most of the time. My ground floor bedroom with normal cement covered brick with outside roof and thin fiberglass mat and one large window is 25 square meters and has an 18k unit but when it failed decided to have a backup just in case and installed a 9k unit to allow enough for sleep hours. That was about 4 years ago and have only started the 18k unit on about 3 days for more than test since then as 9k takes care of room 24 hours a day. But I do not like freezer conditions so normally run it at 26-28 degrees - if you like meat locker feeling then it probably would not be enough.

18000 Btu for a 25 m² room is overkill anyway, but what the OP suggests to use 2 x 9000 Btu in a 50 m² room is way undersized.

I would say the minimum should be 2 x 13000 Btu, but if it was me I would go with 2 x 18000 Btu.

There should also be considered if the aircon is mainly to be used during day or night time. During night time you will get away with a smaller unit than is needed during day time.

Edited February 25, 2014 by JesseFrank

[FACTOR]

As said it is easy to buy too much so highly advise the two units for the 50 square meter as you will most likely end up only using one most of the time. My ground floor bedroom with normal cement covered brick with outside roof and thin fiberglass mat and one large window is 25 square meters and has an 18k unit but when it failed decided to have a backup just in case and installed a 9k unit to allow enough for sleep hours. That was about 4 years ago and have only started the 18k unit on about 3 days for more than test since then as 9k takes care of room 24 hours a day. But I do not like freezer conditions so normally run it at 26-28 degrees - if you like meat locker feeling then it probably would not be enough.

18000 Btu for a 25 m² room is overkill anyway, but what the OP suggests to use 2 x 9000 Btu in a 50 m² room is way undersized.

I would say the minimum should be 2 x 13000 Btu, but if it was me I would go with 2 x 18000 Btu.

There should also be considered if the aircon is mainly to be used during day or night time. During night time you will get away with a smaller unit than is needed during day time.

Yes, I see your point. And that is in keeping with your previous post about 800 btu per sq meter. Ok, now I'm going round in circles, but I'll get it figured out. Thanks for the help.

[JesseFrank]

As said it is easy to buy too much so highly advise the two units for the 50 square meter as you will most likely end up only using one most of the time. My ground floor bedroom with normal cement covered brick with outside roof and thin fiberglass mat and one large window is 25 square meters and has an 18k unit but when it failed decided to have a backup just in case and installed a 9k unit to allow enough for sleep hours. That was about 4 years ago and have only started the 18k unit on about 3 days for more than test since then as 9k takes care of room 24 hours a day. But I do not like freezer conditions so normally run it at 26-28 degrees - if you like meat locker feeling then it probably would not be enough.

18000 Btu for a 25 m² room is overkill anyway, but what the OP suggests to use 2 x 9000 Btu in a 50 m² room is way undersized.

I would say the minimum should be 2 x 13000 Btu, but if it was me I would go with 2 x 18000 Btu.

There should also be considered if the aircon is mainly to be used during day or night time. During night time you will get away with a smaller unit than is needed during day time.

Yes, I see your point. And that is in keeping with your previous post about 800 btu per sq meter. Ok, now I'm going round in circles, but I'll get it figured out. Thanks for the help.

Even at 600 Btu/m² you would need 30.000 Btu for that room, so 2 x 13000 is a minimum, unless you want to have the outdoor unit running continuously.

Believe me 2 x 13000 Btu will cost you little more in purchase, but will save you money over time.

[JesseFrank]

Let me tell you something.

I have 2 bedrooms of 15 m² and 22 m² , each have an identical Daikin 12000 Btu inverter aircons installed.

In the smaller room the temperature is set at 26°c while in the bigger room it's set at 27°c. Over the past 3 years my electricity bill has every month been in a range of 200 Baht between highest and lowest bill.

The last 2 months I didn't use the aircon because it was about 20°c outside, but used the ceiling fan in the lowest speed instead.

Both months my electricity bill has been in the top range from the past 3 years.

Since I received the latest bill 3 days ago, I have switched on the aircons again at night, however the temperature outside is still below the set temperatures.

[FACTOR]

Ok, Jesse -- I believe you. You make a strong argument. Believe me; I'll re-read your post when I'm sober to take serious note of it and make my AC plans.

Thanks.

[JesseFrank]

Ok, Jesse -- I believe you. You make a strong argument. Believe me; I'll re-read your post when I'm sober to take serious note of it and make my AC plans.

Thanks.

When you're sober?

When I sober up I usually don't remember my good intentions from the previous night anymore.

[FACTOR]

You and me both. And that's why I need a good AC system-- helps the head sometimes.

[scotsman]

I was told by a AC store a longtime ago that my living-room- kitchen open plan of 50 sqm size was 26,000 btu so we bought it silly me for trusting them. This unit has been working alright in the night time but the compressor never goes off if you set it at 25 deg but at 30 deg it will go off and on depending on how hot it is.. Now its too old and does not work as good as it did so we have just bought a new one. As we don't have anywhere to install another one to make it 2 units we decided to install a new one at the same place as the old unit and its a carrier 31,400 btu as I used the calculation of 600 btu per sqm. The shop we bought it from is the Carrier agent on Sukhumvit road not far from Soi country club road and the nice man again tried to sell us a Hitachi at only 28,000 btu so they don't have any idea about what size you need lucky for me I read what you guys say on TV. So we hope when we get this installed in a few weeks that we have a good air-con unit for our living-room-kitchen.

Regards

Scotsman

[maswov]

So many factors to consider such as area of exterior walls, number of windows and doors, exterior shaded or not, exterior facing N S E or W, insulation if any, how well built the structure is as in air leaks, number of persons and animals in the house as well as other heat loads such as computers, TVs, refrigerator etc.

I doubt you will have the calculations done to get the proper size but as stated earlier in the larger room should do 2 smaller ones to compensate for varying heat loads. Also spend the extra money for a unit with a variable speed compressor, the compressor will remain on but at a reduced energy consumption, when the compressor turn on there is a spike and more energy is consumed at that point. More efficient to run at a reduced rate rather than cycling on and off frequently.

[how241]

You and me both. And that's why I need a good AC system-- helps the head sometimes.

I have a small condo, 26 meters, and the 9,000 BTU unit cools it off fast. Although some stores will recommend 12,000 BTU, almost all the units have 9000 and it works well for a 26 meter room. Edited March 1, 2014 by how241

[jacksam]

What is wrong with all you people. The OP can get all this from a thing called the internet. <deleted>.

[Crossy]

What is wrong with all you people. The OP can get all this from a thing called the internet. <deleted>.

Er, not wishing to speak out of turn, but this IS the internet is it not?

[Mudcrab]

What is wrong with all you people. The OP can get all this from a thing called the internet. <deleted>.

This is the internet <deleted>

haha beat me to it Crossy

Edited March 1, 2014 by Mudcrab

[misterphil]

I have a 56 sqm living room and I have 1 x 18,000 BTU and 1 x 12,000 BTU I set them both at different settings. The 18,000 is installed where we sit watching TV at 26 degrees, and the 12,000 is in the dining area and set at 27. I also have 2 ceiling fans that move the air and keep the whole room cool. They are both Daikin Inverter type. Pay the extra and get the Inverter type as you will save 40% on electric bills. Homepro said I needed 2 x 18,000 BTU air conditioners to cool a room in my old house, and that was 32sqm. I have no idea where they get their calculations from, if you go there, they have a chart next to the AC's.

You have to take into consideration if you have the sun shining through your windows too, as that will make a difference to the size of BTU you will need. If you have South facing windows like some of mine are we have to close the curtains as the heat coming through the windows heats up the tile floors, and thats all more work for your AC.

You need to make sure you get the right size BTU for your room because if its too small it will run constantly and the compressor in the outside unit will burn out quickly. It has to have time to cool down by cutting in and out as and when required.

So to answer your question. I have a 56 sqm living room and I have 1 x 18,000 BTU and 1 x 12,000 BTU and they work fine, cut in and cut out and the electric bill is around 3,500 baht a month. We also have an AC upstairs in the bedroom but I don't know what size that is, but we use it every night set at 26.

[4u2mad]

Mate, with all this conflicting info, I'd just move somewhere cooler

[Crossy]

Mate, with all this conflicting info, I'd just move somewhere cooler:w00t:

Nothing conflicting, MisterPhil agrees exactly with post #2

[jacksam]

<deleted> yes this is the internet. Maybe if I wanted to know the recording history of Bob Dylan I could Google it or post it on thaivisa . You blokes need to get out more

[Naam]

Thanks for all the good advice. Now, I'm thinking of going for two 9000 btu units in the large -- 50 sq mt -- room. Run them separately depending on what part of the room I'm in. Makes a lot of sense.

Thanks.

it does not make any sense at all when you look at the price difference 9,000/12,000 btu/h. besides, "good advice" without knowing basic facts such as heat load on the room of the "good adviser" and the heat load on the room you want to cool is "bad advice".

extremely "bad" is the idea to cool a room of 50m² with a total of 18.000 btu/h assuming it has to take an average heat load during the hot months. but you should be OK if you are happy at a room temperature of 28ºC when the ambient temperature is 35-36ºC.

[Kaoboi Bebobp]

Great web resources for sizing air cons for rooms:

Energy Star

This Canadian government source has both metric and Imperial.

This Thai expat site was very useful

When I bought and had installed a/c a year ago, I found the charts at big Pattaya stores had estimates way too high, based on comparisons with the above web sites. I went with the BTU sizings from the above sites for a long bedroom and it was perfect. Note: all the sites say you an oversized a/c unit will not dehumidify your room adequately. Although it may feel cool, it's still damp.

[Naam]

Note: all the sites say you an oversized a/c unit will not dehumidify your room adequately. Although it may feel cool, it's still damp.

that is indeed correct but does not take two facts into consideration that compensation is possible:

-modern airconditioners have a special dehumidification mode,

-switching fan speed to lowest setting of an older oversized model without dehum function will dehumidy the room to a reasonably low level.

the latter is the "trick" of dehum mode modern units have.