Air conditioner bafflement

[oldmanofhoy]

I have to buy split air conditioners for 2 bedrooms in a new house in Chiangmai; the main bedroom is 4.5m x 4m and the second bedroom is 3.5m x 3m. Ceiling height is standard - around 2.5m I would say. I'm not currently in town so have no idea how well insulated the house is, but assume not that well. The main bedroom has a balcony with glazed doors, and the second bedroom has a window about 2m x1m. HomePro leads me to believe I should get 12,000 and 9,000 BTU units, but everything else I read says that's way over the top, and having done various calculations it seems that 9,000 and 7,000 BTU units should do adequately.

Also I have read that having an overpowered unit means the room cools down well before sufficient moisture has been removed, thus leaving a cool but uncomfortably humid room, so apart from cost grounds that's another reason not to overshoot with BTUs. I have also read that getting a unit with an inverter will help flatten the temperature graph as there will be less turning off and on, as a result of which there will be some power saving.

First question: does all of the above seem correct? Have I missed anything?

Second question: what are the best/most reliable air conditioner brands? Are there any new features that aid comfort or economy I may not be aware of?

Third question: where's the best place to buy air conditioners. HomePro seems expensive; we have also got prices from a company called Niyom which are a bit cheaper like for like, and include all the pipes, cable, ducting etc. required as well as the actual fitting. Are there other better places anyone can recommend?

Fourth question - what kind of maintenance and cleaning are required for air conditioners? Coming from a temperate climate, I've only ever experienced air conditioners in hotels before, so have no idea of the upkeep requirements. Is this something one can do oneself, or better to get a maintenance contract (if they exist. All replies gratefully received

[oldmanofhoy]

As you can see that was my first post. How do I get paragraphs to separate properly? My draft was properly paragraphed, but when I went to preview it was not but I could see no way back to edit the post, so pressed on.

[AJ Alex]

I hope this gets answered well as I have a lot of similar questions

[tonytigerbkk]

Try searching on Google for 'BTU calculator'.

On these programs you simply type in the dimensions of your room and the calculator will give you the recommended BTU for your room.

[oldmanofhoy]

I've done that - I'm just seeking corroboration from those with experience that the figures I have come up with seem correct and I haven't overlooked anything, plus answers to all the other questions

[luxoretired]

there is lots of info in the diy forum here ,in a nutshell dont get a unit too small ,the roof temperture is about 60c so this is hovvering on your head well into the night .so insulate well.use converter (do not confuse with reverseable )you may need up there heat in winter so reversable is also required.inverter is that the compressor runs more but at a slower speed therefore less electric .my 40sq mtr living room at this moment at 38c outside is using 600watt so about 2 hours for 6bht.home pro is more expensive but you could find a deal .if you can buy in december as the demand is low and more bargains .i used a thai shop but cannot read the name ,it had good prices and good service so look around .once again ...insulation !floor walls and CEILING !

[bangmai]

I agree with their numbers...12K and 9K.....If anything the 12K might be too small...I think I've seen 13K, but mostly they go from 12 to 18. Your attic could easily be 65C. If your doors faces west; that is also an issue. But I would go with 12/9 and then consider steps to ventilate/insulate the attic. Make sure the condensing unit has very free airflow, as it is giving off a lot off heat. That's probably more important than having it in the shade or under cover...they put them on the roofs all the time. And yes, you did wait until the worst possible time of the year to get it done....I like SiamTV, but they are technicians; not engineers. 13 EER is plenty, you will never get back all the extra money in a 22 EER, high end Japanese model. I don't like Mitsu, and Trane is over-engineered like an Audi...I do like Carrier, York, and Panasonic.....some are louder than others, but they will actually drown out the jets and dogs.

[masuk]

Don't assume that there will be ANY insulation. There almost never is.

[Rancid]

Just hunt around for prices, sometimes an a/c shop gives better service.

Just picked up a new model 12 Samsung at Big C for 10,900 installed. Once the real heat hits prices usually go up.

Edited March 11, 2015 by Rancid

[lopburi3]

I fully cool my bedroom with 9k unit and it is about 26 sm so your largest at 18 sm should be fine at 9k (I use 24 hours but ground floor and no large windows - for night use 9k should be fine and probably most days. 9k is about the smallest unit so would get same for both rooms. If only one to get much use would get inverter for that. Recommend you have air conditioner professional clean every six months (here in Bangkok one even 10 months has resulted in complete blockage for fan coil unit - and fliters were cleaned weekly). There is a lot of dirt that gets through and needs to be removed with pressure cleaning.

I have two Panasonic 9k units (normal compressor) and one Mitsubishi 9k inverter that all seem to work well. (and are replacements for much larger units - normal recommendation is over the top here unless you want meat locker temps (but some seem to want that). We prefer temp in the 26-27 degree range - if you want low temps then the stronger units will be required.

You may find a local person who maintains units can sell you a unit at a lower price as some have wholesale access.

[sfokevin]

You also might want to consider getting the inverter models... Especially in a bedroom... Then you get a constant coolness instead of an on/off coolness when the compressor turns off & on... It makes sleeping more comfortable and when you run it eight hours all night you will save on electricity enough to pay for the additional up front cost...

[femi fan]

Interesting to read.

I've been quoted roughly similar prices at niyom panich, which includes fitting.

But reading one of the threads in the diy forum, i noted people, probably in bangkok, talking about prices of 1 baht per BTU, which is quite a bit cheaper than niyom panich.

Which leads me to asking posters if they can recommend any actual air-con shops in town?

The other question i have is that i'm only likely to use these aircon units i buy for just the summer months, ie only about three months a year. Does that prolong their life, or will the lack of usage for most of the year cause a problem?

[bangmai]

it's good to run them for a few hours every couple of months. It will prevent the seals from deteriorating.

[Gonsalviz]

You also might want to consider getting the inverter models... Especially in a bedroom... Then you get a constant coolness instead of an on/off coolness when the compressor turns off & on... It makes sleeping more comfortable and when you run it eight hours all night you will save on electricity enough to pay for the additional up front cost...

Unless you have a power surge. That cost me 16,000 Baht.

[femi fan]

You also might want to consider getting the inverter models... Especially in a bedroom... Then you get a constant coolness instead of an on/off coolness when the compressor turns off & on... It makes sleeping more comfortable and when you run it eight hours all night you will save on electricity enough to pay for the additional up front cost...

Unless you have a power surge. That cost me 16,000 Baht.

Could you explain more on that? Is a power surge a power cut? We get power cuts frequently in the rainy season, and sometimes for no reason whatsoever at any time in the year.

[femi fan]

it's good to run them for a few hours every couple of months. It will prevent the seals from deteriorating.

Noted!

[Tywais]

I'll give you my personal experience. We have a 2 story house with 3 bedrooms on the top floor. Being the top floor of course it is the hottest part of the house due to hot air rising from the 1st floor and of course the roof.

One of our bedrooms is about the same size as your first 4.5x4 meter one and we have a 9k BTU unit in it and works fine. It has East and North facing windows so gets the morning sun but only the north gets the afternoon sun. The north windows is actually the whole wall with dark glass sliding doors as it is on one of the balconies.

The master bedroom is quite large at 50-55 sqm with west and north glass and again a balcony with all glass sliding doors front for the north. That one we have an 18,000 BTU unit that works well but at the very hottest of days such as a couple of days in April just keeps up due to the west brick walls absorbing heat. But 98% of the time it is sufficient. No roof insulation as far as I know. The 1st floor living room has an 18,000 BTU unit but never used as it is well shaded on all sides and insulated by the 2nd floor.

So 9k for both of your rooms will be fine, even 7k for the smaller one but 9k is a more standard size. Of course a lot depends on any insulation and how much glass and the direction the glass is facing.

However, the thermostat is kept at 26.5 C for the master bedroom. The smaller room with 9k BTU sometimes is set to 24-25 and can keep up.

[billphillips]

The best units for you would be 2 x 12 / 13,000 btu. I can't recommend a 9,000 btu unit because it cost nearly the same as a larger unit and a possibility exists that it cannot effectively cool the room thus causing the compressor ( the expensive to run bit ) to run continually. The running costs for a 9 and 13k btu are similar as well.

I don't know who gave you the info about humidity ... It sounds very stupid to me. Most, if not all, units have a drying mode but it's not necessary to use except if drying laundry or similar in the room.

฿13,000 each should be achievable. I recently fitted 3 Samsung "triangle" split units for ฿38,000 all in, with a local installer. The big chains were much more.

Ceiling insulation is a good idea above air coned rooms but most don't have it. You can't actually save that much with insulation, presuming you will be using the cooling mostly at night. Insulating against heat is not quite the same as against cold. Solar gains (windows allowing sunlight in) are much more of a problem than heat from the roof.

Don't buy an inverter type unit. The cost at the moment can never be recovered in running costs during the life expectancy of the product.

Don't set the room temp too low. An unrealistic temp cannot be achieved and will result in high fuel bills and a chesty cough. Start at around 26c and see how that goes.

Don't think too much about it ! Select a well known brand with the latest up to date model and go for it. Enjoy your air-con.

[Tywais]

The best units for you would be 2 x 12 / 13,000 btu. I can't recommend a 9,000 btu unit because it cost nearly the same as a larger unit and a possibility exists that it cannot effectively cool the room thus causing the compressor ( the expensive to run bit ) to run continually. The running costs for a 9 and 13k btu are similar as well.

Oversizing is a bad idea for a variety of reasons. I will just post a few of the many links that explain it. Due to short cycling, humidity removal is reduced, energy costs go up, uneven cooling - that is from hot to cold to hot. Here is a quote from one of them.

There are three reasons:

First is that an air conditioner is most efficient the longer it runs. If it is too big, it will run for a couple of minutes at a shot, whereas, if it is the right size, it will run much longer – on the hottest afternoons of the year, it should run all the time. This delivers the cold air at the lowest cost and more evenly.

The second is that the air conditioner is also a dehumidifier. Here on the West Coast we spend about 20% of our air conditioning money on taking moisture out of the air. If the unit is too big and spends more time off than on, the coils won’t get cold enough for a long enough period of time to condense enough moisture to be effective in removing moisture from the air.

The third problem with oversizing the air conditioner is that if you buy too big a unit, you are simply wasting money. A properly sized unit has a fudge factor built-in, so that once a proper heat loss/gain calculation has been done, buying a larger unit than called for is unnecessary.

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/55157/Why-an-Oversized-Air-Conditioner-Is-a-Bad-Idea

http://buildingdoctors.com/home-cooling-systems

http://www.weeks-service.com/oversizedairconditioner.htm

http://www.diynetwork.com/electrical/keeping-it-cool-how-big-should-an-ac-unit-be/index.html

[Tywais]

As this is not really Chiang Mai specific I'm moving it to the DIY forum where a lot of topics on the subject are and several knowledgeable members on the subject are.

[IMHO]

This is the most accurate AC sizing guide I've found, based on real world experience:

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

Using that along with your description (bedroom only cooled at night so little/no sun, but with poor insulation) you should be using 800 BTU/sqm as your minimum/baseline.

Based on that, and rounding it off to standard AC sizes, your larger bedroom should have 15K BTU, the smaller one 9K.

[NeverSure]

One of the reasons the starting and stopping of a bigger unit uses electricity is that the starting circuit in that big motor uses a lot more power than the run circuit. It takes a lot of power to start up, but not so much to run. This isn't a lot different than running a car from stop sign to stop sign as opposed to cruising on an open highway (in a way.)

OP, to edit your post, hover your mouse in the area to the left of the "multi quote" button, lower right, and you will bring up the word edit which you click on.

Edit, LOL. I don't know the amount of time, but the ability to edit expires after a certain amount of time.

Cheers

Edited March 11, 2015 by NeverSure

[IMHO]

The master bedroom is quite large at 50-55 sqm with west and north glass and again a balcony with all glass sliding doors front for the north. That one we have an 18,000 BTU unit that works well but at the very hottest of days such as a couple of days in April just keeps up due to the west brick walls absorbing heat. But 98% of the time it is sufficient.

That is hugely under sized, and could only ever possibly cool the room after dusk - even then you'll want to be a late to bed type, so nature can help with the cooling first.

I'm not telling you anything you haven't already experienced though

[IMHO]

One of the reasons the starting and stopping of a bigger unit uses electricity is that the starting circuit in that big motor uses a lot more power than the run circuit. It takes a lot of power to start up, but not so much to run. This isn't a lot different than running a car from stop sign to stop sign as opposed to cruising on an open highway (in a way.)

If your'e going to be using AC daily, oversize a little (just +100 BTU/sqm makes a big difference in temperature deltas), and then buy an Inverter model - then you have the performance needed even on the hottest days, and won't be wasting electricity on all the others.

There is simply nothing worse than an AC that fails to cool sufficiently when you need it the most (the hottest days of the year).

[maderaroja]

This is the most accurate AC sizing guide I've found, based on real world experience:

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

Using that along with your description (bedroom only cooled at night so little/no sun, but with poor insulation) you should be using 800 BTU/sqm as your minimum/baseline.

Based on that, and rounding it off to standard AC sizes, your larger bedroom should have 15K BTU, the smaller one 9K.

The website may be accurate, but it is unreadable.

[skatewash]

This is the most accurate AC sizing guide I've found, based on real world experience:

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

The website may be accurate, but it is unreadable.

Take a look at the website using the Google Chrome browser and it will do a machine translation of the content from Thai into English. It's a statistical-based translation so hardly 100% accurate, but I find it's usually enough to get by.

[FredLee]

I think the 12,000 and 9,000 estimates are correct. I have two rooms almost exactly the sizes you have, and these are the size of the split units I have in each of them. I am also in Chiang Mai. I purchased my units from Dragon Air on highway 1001, very near to Theppanya hospital. Their quoted price included the installation, and you can also purchase a one or two year cleaning/maintenance contract from them. I went with the Mitsubishi Slim Econo units. Be sure to bargain with them. When I informed them that I had a slightly lower estimate from another shop, they reduced their price by 1000 baht per unit.

[ToddinChonburi]

We have a Daikin in a 40 sqm condo facing the north and it seems to do a fine job and just had it power washed. WOW it was really dirty so the cleaning every six months would be a must. The humidty thing is you will always be playing with the temp because sometimes 23 will be more comfortable at night than 24. our fan has 5 speeds plus Auto, I normally run on 2 and does a great job. Somedays put on 3 when we both shower and humitidy outside in upper 80 percent.

[SOUTHERNSTAR]

You can calculate with the cubic meters the BTU's needed but it depends on what temp you want to maintain. If you want it freezing go for the recommended BTU's or more. If you however run the aircon only for an hour or two after going to bed and the ceiling is insulated you can get away with a smaller unit. I would recommend that you workout the position of the a/c's. I hate an a/c that blows directly on me when I sleep and thus installed our ones off center in the bedrooms.

[bkksiam]

I bought the inverter model. One of the things I considered in my purchase was how much sound the unit makes. I wanted something quiet. not sure as well if you have to consider number of people typically in the room. I also put a weather strip on the bottom of my bedroom door (minor insulation). In general, for cleaning and servicing, depending where you live, you might want to buy something that technicians in your area are used to.