Air Conditioner BTU

[chuang]

Hi there, need some advice...for a bedroom 5 by 6 meter and other 5 by 3 meter how much BTU must the air conditioner be....thanks you..

[Rooo]

Moved to housing forum.

[bankruatsteve]

18000 & 9000 BTU.

[burgerking]

My advice is to get an airconditioner thats more powerful for the room, as it won't have to work as hard. If 9000 BTU room, i'd go for 12000 and so on.

[Naam]

an airconditioner works when it's switched on and does not mind under which conditions it works. no conditions exist that make an aircon work harder or less hard.

[gerry123]

Air Con Size Chart

Started by wpcoe, 2006-10-31 11:09

in the search feature

[trd]

an airconditioner works when it's switched on and does not mind under which conditions it works. no conditions exist that make an aircon work harder or less hard.

I have a 9000 BTU in a bedroom and it is working too hard because it cannot reach the temperature because it is underpowered and the compressor never switches off. I think this is what he means by working too hard. Edited April 11, 2015 by trd

[Anthony5]

There are several calculations to measure your BTU need.

In the shops they will advise 600 BTU/sqm of your room, because they know the higher the BTU the more expensive, and they want to make a sale.

The engineers from Daikin Thailand calculate 800BTU/sqm, because they want to make sure the room cools fast enough, otherwise you may be discontent.

I think the golden midway of 700BTU/sqm is the way to go.

[IMHO]

There are several calculations to measure your BTU need.

In the shops they will advise 600 BTU/ of your room, because they know the higher the BTU the more expensive, and they want to make a sale.

The engineers from Daikin Thailand calculate 800BTU/sqm, because they want to make sure the room cools fast enough, otherwise you may be discontent.

I think the golden midway of 700BTU/sqm is the way to go.

Even that is an oversimplification...

600 BTU/sqm is the baseline for a bedroom with cooling only at night.

There are several factors that mean you may need to increase the BTU/sqm.

This is the most accurate and realistic BTU/sqm guide I have seen online:

http://www.rung-ruengair.com/new/InformationAir.html

You'll need to translate if you can't read Thai though.

Using the appropriate range from there, you will never be let down, even on the hottest days.

[IMHO]

I think the golden midway of 700BTU/sqm is the way to go.

I had 686 BTU/sqm in a 35sqm North facing bedroom, well insulated ceiling/roof, no Westerly sun at all but because it has a small dormer (2M wide with 5.5M high vaulted ceiling) it was just woefully inadequate. That's when I started researching on all of the factors. That room ended up needing 1000 BTU/sqm to work.

[Naam]

an airconditioner works when it's switched on and does not mind under which conditions it works. no conditions exist that make an aircon work harder or less hard.

I have a 9000 BTU in a bedroom and it is working too hard because it cannot reach the temperature because it is underpowered and the compressor never switches off. I think this is what he means by working too hard.

you are missing my point but you are excused interesting fact as far as conventional compressors are concerned which run at constant speed (not inverter driven) the life span is shortened by on/off switching.

[Crossy]

This is the most accurate and realistic BTU/sqm guide I have seen online:

http://www.rung-ruengair.com/new/InformationAir.html

You'll need to translate if you can't read Thai though.

Using the appropriate range from there, you will never be let down, even on the hottest days.

Google Chrome translates that page very well, great link

From the link;-

Calculate BTU air conditioner

BTU = area (W * L) * variables.

Variable heat divided into two levels.

700-800 for the bedroom Or a room with less heat. (At the sun or a little low ceiling or room where the air during the night).

800-900 for the living room Or a room with a heat medium - high (sun room. The west Or the air during the day)

900-1000 for office Fitness Or a room with a lot of heat. Or ceiling (sun room. The west On the top floor Or the air during the day)

1000-1200 for shops The restaurant door, often hair salon or office with many people.

If the ceiling height of 2.5 meters with a large number of people. Or a computer should BTU plus an additional 5% of the normal value.

[sometimewoodworker]

On our bedroom with reasonable windows, but virtually no insulation other than thin squares over the drop ceiling panels, almost no sun on the walls. We have just installed a Mitsubishi MrSlim non inverter it is easily big enough for us. It's capacity is 512BTU sqm or 165 BTU cu meter. The outside unit is mounted so it gets no sun on it.

It can easily drop the temperature by 15 degrees without running full time, however we don't often drop more than about 8 degrees.

Edited April 12, 2015 by sometimewoodworker

[thuisinthailand]

There is a BTU calculator here:

http://www.calculator.net/btu-calculator.html

We are also trying to figure out what kind of aircon to use for our bedroom. We'll soon move to another house. It's close to the beach (we're on Samui) and the bedroom is upstairs (wooden floor and wooden walls). Only use aircon in evening and night, max 12 hours, never during daytime.

So what to do... Room is 4,5 x 5,5 (around 25 square meters), not too high (2,30 meters). Inverter or not? What brand? Mitsubishi is the most silent, they say. We're getting quite crazy about all the different options and discussions, here and elsewhere. Any sensible advice?

[trd]

This isn't about BTU, the subject of the thread, but let me just get this of my chest. I've come to the conclusion that the build quality of air cons is crap, no matter what brand it is. Sooner or later, they all get noisy because of wear on motor bearings and other mechanical linkages. You'd think that by now they would have come up with better technology. There, I'm done.

[IMHO]

There is a BTU calculator here:

http://www.calculator.net/btu-calculator.html

We are also trying to figure out what kind of aircon to use for our bedroom. We'll soon move to another house. It's close to the beach (we're on Samui) and the bedroom is upstairs (wooden floor and wooden walls). Only use aircon in evening and night, max 12 hours, never during daytime.

So what to do... Room is 4,5 x 5,5 (around 25 square meters), not too high (2,30 meters). Inverter or not? What brand? Mitsubishi is the most silent, they say. We're getting quite crazy about all the different options and discussions, here and elsewhere. Any sensible advice?

That calculator is missing two important inputs: ambient temperature and humidity. Generalisations for other countries that don't have the heat and humidity of Thailand will usually have you under-sizing.

As for you room, I would start at the baseline of 600 BTU/sqm then would add 100 BTU/sqm for the poor insulation - so round it up to 18K BTU. Another way to look at it is the next step down is 12K BTU, which is only 480 BTU/sqm and well under-sized for the task

Seeing as the machine will be used daily for 12 hours, you will definitely see ROI on an inverter unit.

When is comes to noise, don't believe the word of a salesman - read the specs. While some smaller units can get very quiet, as you move up on cooling capacity, air volume of the inside fan also increases - which increases noise.

e.g. The Daikin Smart R32 9K BTU is just 22dB inside (that's almost undetectable), while the Saijo Denki Intelligent inverter at this size is 24dB (still quiet, but not as quiet). However, at 18K BTU the Daikin is 31dB and the Saijo Denki is 28dB - i.e. the tables have been turned.

Given that you are talking about a wooden house with assumedly poor sound insulation, I'd say anything up to the low 3x dB range will still seem quiet enough.

Edited April 15, 2015 by IMHO

[IMHO]

This isn't about BTU, the subject of the thread, but let me just get this of my chest. I've come to the conclusion that the build quality of air cons is crap, no matter what brand it is. Sooner or later, they all get noisy because of wear on motor bearings and other mechanical linkages. You'd think that by now they would have come up with better technology. There, I'm done.

All AC's do use a very similar design - which is a good thing because it means that anyone that can service an AC, can service your AC

[thuisinthailand]

Thanks IMHO, that is very helpful. We calculated a 18K BTU as well, so that seems a no brainer now.. As for the noise, I don't mind some of it, bc it also helps to reduce noise from outside (if any).

[thuisinthailand]

One more thing: how about the electricity? I've understood that for a water heater for example, in case the electric meter is marked 5/15, maximum heater capacity is 3,5kW. Is there a similar check to be done for air conditioners, or do they basically fall into the same category? (given that we will buy a 18K BTU one).

[bankruatsteve]

From what I have seen, most installations with a 5/15 meter don't have the correct wire size for stuff that draws 10a or more. My 18K BTU A/C draws about 6.5 amps - so you might be good but make sure at least 2.5mm2 wire.

[thuisinthailand]

The wiring inside the house has been upgraded a year ago including a new electricity board, that seems good news, but I will check the outside meter next time we're at the house (did not move there yet).

[thuisinthailand]

Sorry to bother you with one additional question: the bedroom is 25 m2, but due to the specific construction it would be very easy to downsize the room with the use of a curtain (in the past it used to be two smaller rooms), size would then be 4,5 x 2 meter. Does this make sense and does it work? And do you then still advice to have a 18K BTU ( I would be inclined to think so due to the wooden construction of the room) or is then 12K BTU a better solution?

[IMHO]

Sorry to bother you with one additional question: the bedroom is 25 m2, but due to the specific construction it would be very easy to downsize the room with the use of a curtain (in the past it used to be two smaller rooms), size would then be 4,5 x 2 meter. Does this make sense and does it work? And do you then still advice to have a 18K BTU ( I would be inclined to think so due to the wooden construction of the room) or is then 12K BTU a better solution?

A curtain doesn't sound like it's going to make much difference AC wise.

[thuisinthailand]

Checked the house again, meter is recently upgraded to 15/45 amps, with new cables, so we're ok for the 18k BTU...

[thuisinthailand]

Have read a lot of threads about the question: inverter or not? Does it really save that much money on the electricity bill? If buying a Mitsubishi 18K BTU, the price difference at a well known local shop here on Samui is about 6,000 baht (28,900 versus 34,900 baht). Would it be worth to buy the inverter model?

[IMHO]

Have read a lot of threads about the question: inverter or not? Does it really save that much money on the electricity bill? If buying a Mitsubishi 18K BTU, the price difference at a well known local shop here on Samui is about 6,000 baht (28,900 versus 34,900 baht). Would it be worth to buy the inverter model?

Inverters will use less electricity, and provide more stable temps - if the AC will be used daily you'll get pay-back, if it's used infrequently you might not though.

[kokesaat]

We have two Daikin 18,500 inverter air cons.  We're planning a months-long trip and I'd like to set the ACs to come on for 2 hours or so each day to keep the rooms fresh (maybe set the ACs on dehumidify).  The problem I have is.....the timers on the ACs don't reset if the power shuts off and comes back on.  

Does anyone know of a 'simple' way to deal with this?   There will not be anyone in the house while we're gone.

Many thanks

[Kwasaki]

On 4/11/2015 at 7:45 PM, Naam said:

an airconditioner works when it's switched on and does not mind under which conditions it works. no conditions exist that make an aircon work harder or less hard.

 

Not too sure what you mean, so what reckon, had fitted after air-con guys working out size a 12000 btu in upstairs main bedroom,  in the hot season it was difficult to get a comfortable stable temperature in the room even after insulating the ceiling.

Got a 24000 one fitted and it chugs along nice and gentle and better like not having to work so hard,  electric bill reduction as well. 

Different make but previous one works OK in one of the smaller bedrooms downstairs.

[Gary A]

I think the size you need depends entirely on the room. Sun or no sun and under roof or under another room. My condo bedroom is 24 square meters, has no sun and has other rooms on top. It has a 12,000 BTU unit that just died. It would cool the room quickly and when running would cycle on and off quite often. I'm considering replacing it with a smaller unit that won't be cycling on and off so often. If I am able to find a 10,000 BTU unit or even a 9,000, that should do the job. I have a 12,000 BTU Panasonic inverter type in my computer room at home and don't think it was worth the extra money.

 

Samsung units are supposed to be a bad choice but my home bedroom has a 9,000 BTU Samsung unit and it is now 10 years old and has never had a problem. I'm not sure which brand to buy.