Air Con - Sizing For Living Area?

[Pikey]

Here's hoping to get a few consistent replies:

We're thinking of installing A/C in the living room which works out 45sqM give or take. I've spent the morning working out via the internet that a 12-14,000BTU unit should do the trick. I then called into Dragon Air who specified a 24,000BTU unit - quite some difference, both in power and price.

I then checked this thread

In it people were saying that Thai units seem to be way over-spec'd compared to their Euro/US & Aus counterparts. I appreciate that a lot of this may be down to environmental factors as well as how well the house is constructed and insulated. I also understand that I don't want to get an underpowered unit and have it running flat out all the time struggling to keep things cool. On the flip side, neither do I want a huge unit that is constantly cycling as I understand that it will not run long enough to de-humidify the air.

So, here's the scenario:

Brick built Thai bunglaow

Uninsulated tiled roof

1.5 metre overhang from the eves all around

West facing aspect where the unit will be installed

Condensor will be in the shade at all times

Target room temp of about 25 deg C for about 8 hours a day

Any advice on BTU spec, brand (Daikin seems to be my favourite at the moment) and whether an inverter unit is worth the extra cost given the intended use.

With thanks in advance,

Pikey.

[Crossy]

The Thai standard 600 BTU / m² comes out at 27,000, that does seem to over-estimate mind. How did you arrive at 12k?

With a large area two smaller units would be wise, you only need to run one during the cool season so you don't run in to the oversized unit problems.

[brommers]

I bought a new & reasonably well insulated house 6 months ago & got Dragon Air to survey & quote.

Yes they were a recommending slightly more capacity than my amateur calculations but I can only say that they were right. In fact on some of the really hot days earlier this year I wondered if we should have had an even bigger unit in one of the rooms. It seems to me that the US & Euro calculation tables are not applicable here fr whatever reasons. And the original installation process and the after-service that we have had from Dragon has been excellent.

What brand you select is entirely up to you but we went for everyone's favourite Mitsubishi because in our previous house we never had any problems. The new units are quiet and seem to be very energy efficient. So we have no complaints.

Good luck. I value my comfort very highly but I am not a big spender, but I would advise you to let professional experience prevail. Investment in a good system will pay dividends in the long run & after sales service is a key element in the equation.

[HullyGully]

Dragon Air looks about right 24000 BTU's

Power supply would be around 16amps, price est 24k depending on make, I like panasonic / National

This is a fairly big AC, make sure you have the power to run the unit, fused at 20amp

[KRS1]

I purchased a 24000 btu ac unit for my 40 sqmeter condo and it was too big, it had problems cycling correctly.

Id go with a 14000-16000 btu unit and make sure its a digital thermostat/temperature controller. The old dial controllers are junk.

[Naam]

So, here's the scenario:

Brick built Thai bunglaow

45m²

Uninsulated tiled roof

1.5 metre overhang from the eves all around

West facing aspect where the unit will be installed

Condensor will be in the shade at all times

Target room temp of about 25 deg C for about 8 hours a day

12-14000btu/h = no way! 24k btu/h minimum for 25ºC of 45m² (temperature most probably not achievable when outside temperature 33ºC and above).

[market trader]

Very happy I read this post and replies. I also will be buying a new A/C and am sure that had I not read the replies, would have ended up not happy with a unit that is smaller than required.

[Pikey]

Thanks for all the advice guys. I think I'll cruise around a few more suppliers with my specs but it's looking like that using the online sizing calculators from overseas websites results in an under-specified unit for our particular set of circumstances.

Thanks again.

Pikey.

[jollyrog]

@ Pikey..................Here is my experience of 8 years in a two story concrete home with barrel tile roof, no insulation, 8' ceilings, no shade trees built in 2000.

The ground floor is an 84 sq meter great room with living, dining, kitchen, entertainment center and entrance foyer all adroitly arranged for functionality. The ground floor is always cooler as heat rises. I installed a 34,000 BTU unit which will cool the big room down to 25c in 20 minutes then cycle to maintain the temp....the down side is the cost not only of the unit but of electricity. When I replace it I will drop down to a 14-16,000 BTU unit.

Upstairs in the 28 sq mtr master I had installed a 12,000 BTU unit. Twenty minutes before bedtime I turn it on high on the way to the shower and it is 25c

by the time I return. Reset to low fan quiet mode I cannot hear it and it is programed to automatically shut off at a programmed time when a 10" fan turns on.

In the two guest bedrooms of 17 sq mtrs each I use 9,000 BTU units. On the West side at 5 PM it takes it takes a little longer to cool the room and the smaller units have a very quiet operation.

All units are Saijo Denki and I've had no problems with installations or service and the cost is competitive. I have electrostatic filters on all units to filter the air as they cool and dehumidify.

Roger

[alfieconn]

. Twenty minutes before bedtime I turn it on high on the way to the shower and it is 25c

by the time I return

Forgive me for asking Rog but what do you do in the shower for 20 mins

[Naam]

Thanks for all the advice guys. I think I'll cruise around a few more suppliers with my specs but it's looking like that using the online sizing calculators from overseas websites results in an under-specified unit for our particular set of circumstances.

Thanks again.

Pikey.

Pikey, if you are not too restricted by money concerns i would like you to consider Crossy's suggestion "two smaller units" of 12k btuh each. there are days when one of the unit is sufficient and you have the added higher "latent" cooling capacity because of more efficient dehumidification.

i am a big fan of airconditioning (whole house 24/7) but my comfort zone is 26ºC with rather low relative humidity of 50-60%. this cannot be achieved with big units on moderately warm days. without going into rocket science type of explanations, here's the beef:

even though you stated "desired temperature 25ºC" you will feel most probably more comfortable at 26º and 55% humidity than at 24º and 75% humidity. if you shop around you might find a dealer who sells and installs two smaller units for a rather fair surcharge. aircon prices vary widely, last not least because of demand. the latter quite often based on subjective recommendations such as

"buy XYZ brand because

-my mother-in-law got one and she is very happy,

-after we installed XYZ the dogs stopped peeing on the persian carpets,

-buy ABC and receive a 90% monthly refund of your electricity bill,

-QSL aircons are so quiet i can hear the mosquitoes fart,

-with the new LMN unit in my bedroom i save a lot on Viagra, i.e. more cash for Chang.

[luckyluke]

i am a big fan of airconditioning

fan/aiconditioning

[Pikey]

Again, thanks for al the advice so far.

There's been a couple of references to installing 2 smaller units instead of one big one but not being at all familair with the functioning of A/C I don't know. The area we are talking about is a combo living/dining area with the living area being the biggest at 6*6m then add the dining which is roughly 2.5*4m - so imagine a square and an oblong T'd together but open, with no divider.

If I bunged in say a 14,000BTU at the head of the living space and another in the dining area but normally had the dining area one off, surely the cool air would disipate over the entire area and the sensor of the living area unit would then go crazy pumping out air to "fill" the dining area? Alternatively, I'd have to run the dining area one at the same time to balance the situation?

From a layman's point of view, if I had one more powerful one in the living area, where we spend most of the time, it'd be better because we'd benefit more from being closer to the unit's output and wouldn't care too much that the dining area was a bit warmer. Like I said, I don't know the workings of A/C, sensors and air currents so am very open to educated advice.

Cheers,

Pikey.

Edited September 8, 2012 by Pikey

[jollyrog]

. Twenty minutes before bedtime I turn it on high on the way to the shower and it is 25c

by the time I return

Forgive me for asking Rog but what do you do in the shower for 20 mins

Sh*t, shower and shave.....Alfie.....I suspect you've not been in the United States Marine Corps. oooorah !

[jollyrog]

Pikey..........I forgot to mention fans. I have 5 downstairs and 5 upstairs, all with 10" blades (considerably quieter and push almost as much air) with one placed strategically near the air/con being used. The fans are to keep the air moving in the living space being used......the a/c to maintain the temperature. We use fans daily regardless of temperature inside. A cheaper alternative to an oversize air conditioner.

Roger

[Naam]

Pikey..........I forgot to mention fans. I have 5 downstairs and 5 upstairs, all with 10" blades (considerably quieter and push almost as much air) with one placed strategically near the air/con being used. The fans are to keep the air moving in the living space being used......the a/c to maintain the temperature. We use fans daily regardless of temperature inside. A cheaper alternative to an oversize air conditioner.

Roger

the fans move indeed air, namely warm/hot air from the ceiling down to the floor

[moe666]

Pikey you need to measure your windows and door and include them in your heat calculation as they will lose heat faster than the wall. Also its caled A/C that is air conditioner, as Naam mentioned earlier de-humidification is very important the lower the humidity the cooler you will feel even when the temp. is higher. Installing 2 units will help you to save on electricity in the long, the air doesn't migrate that fast so if you are in one section of the room onlyt run that unit. Also you can set the thermostats differently if one unit cannot handle the load then the other unit will kick in to compensate.

One of the first things to do is insulate your roof.

[alfieconn]

. Twenty minutes before bedtime I turn it on high on the way to the shower and it is 25c

by the time I return

Forgive me for asking Rog but what do you do in the shower for 20 mins

Sh*t, shower and shave.....Alfie.....I suspect you've not been in the United States Marine Corps. oooorah !

You do a shit in the shower, disgusting and i'm glad i havn't been in the USMC if thats the type of thing they do !

[Naam]

Pikey you need to measure your windows and door and include them in your heat calculation as they will lose heat faster than the wall. Also its caled A/C that is air conditioner, as Naam mentioned earlier de-humidification is very important the lower the humidity the cooler you will feel even when the temp. is higher. Installing 2 units will help you to save on electricity in the long, the air doesn't migrate that fast so if you are in one section of the room onlyt run that unit. Also you can set the thermostats differently if one unit cannot handle the load then the other unit will kick in to compensate.

One of the first things to do is insulate your roof.