Aircon units

[dick dasterdly]

I recently made the mistake of taking room measurements to the store (rather than googling the calculations myself) when buying an aircon unit. There was obviously a major miscommunication as they recommended, and I bought, a 12.52 BTU aircon unit.

It works pretty well in the 'room' in which it is installed, but v badly anywhere else in the open plan area, so I went back to the store and they sent out a technician to take a look.

The technician told me that I needed a 70 BTU unit, and finally googling the calculations - he's right.

This leaves me indecisive as to the way forward. The aircon unit works well enough in the 'room' in which it is installed - but I had it put there for cosmetic reasons as it would look ugly in the living room. My first thought was to move it to the living room (regardless of aesthetic considerations), but that would leave holes in the wall and I don't know any 'handymen' to fill the holes - let alone finding the right coloured paint once the holes have been filled.

Which finally brings me to my question!

I'm v concerned about the cost of running aircon (my elec bills are v expensive already for various reasons), so - does anyone know:-

1) would I be better off buying a similar sized (12.52 BTU) aircon to be placed on a living room wall (the only area I need to be cooled) - bearing in mind it would be running at full power all the time used, or

2) would it be better to buy a 70 BTU aircon that would cool a larger area, but then not be running 'flat out' all the time?

[MJCM]

Lets start from the beginning.

How big is the room you want to cool ? LxWxH

70 BTU ? Do you mean 70.000 BTU ?? That is an aircon suitable for rooms the size of +/- 100SQM, where a 12.000 BTU aircon is suitable for around 16-20 SQM, huge difference and also a HUGE difference in PRICE

Edited May 1, 2016 by MJCM

[lopburi3]

Believe you have decimal points in the wrong position - but 70,000 btu sounds very large - believe best you provide room sizes so people can help using real information.

It likely would be best to have two units - but the size of second unit can not even be guessed at without at least room size - and description of walls/windows would help.

[dick dasterdly]

Lets start from the beginning.

How big is the room you want to cool ? LxWxH

70 BTU ? Do you mean 70.000 BTU ?? That is an aircon suitable for rooms the size of +/- 100SQM, where a 12.000 BTU aircon is suitable for around 16-20 SQM, huge difference and also a HUGE difference in PRICE

The open plan area is 15 X 5 X 3 metres, but the only part of it that I need cooling is 5 X 5 X 3.

Apologies for getting the BTU ratings wrong, I was going by my new aircon which has a sticker saying 12.52 BTU and the technician saying I needed 70. I wondered/hoped he meant 17 until I googled the calculations .

[dick dasterdly]

Believe you have decimal points in the wrong position - but 70,000 btu sounds very large - believe best you provide room sizes so people can help using real information.

It likely would be best to have two units - but the size of second unit can not even be guessed at without at least room size - and description of walls/windows would help.

The technician also suggested another unit installed in the living room (they would be facing each other, but about 7m apart).

Downstairs, double patio door windows/set of windows approx 4m X 1m/another set of windows approx 1.5m x 0.5m. Upstairs landing windows 1m X 1.5m.

And checking this has made me realise that the 5m width doesn't include the kitchen...., which adds another 1.5m in total width from where I'd measured.

But its an odd design, so the width and length vary, as does the ceiling height which is obviously a lot more than 3 metres from the bottom of the stairs to the ceiling of the landing.

[IMHO]

You can't just cool down a part of a space - for part if it to be cool, all of it needs to be cool.

The upstairs landing doesn't factor into to it - if the room is downstairs and the AC's downstairs, that's where the cold is also staying.

So basically, you have a downstairs room of 75sqm to cool. I have the same sized space in my house, also the ground floor of two, which has a total of 60,000 BTU between two AC's: a 24,000 BTU + and 36,000 BTU - and even on > 40c days they do the job without any strain. I wouldn't want any less though, but I certainly don't need any more either.

[sipi]

From my experience Thai air-conditioning tradesmen aren't as dumb as TVF experts pretend they are.

Trust your local technician, he is trying to help.

[dick dasterdly]

You can't just cool down a part of a space - for part if it to be cool, all of it needs to be cool.

The upstairs landing doesn't factor into to it - if the room is downstairs and the AC's downstairs, that's where the cold is also staying.

So basically, you have a downstairs room of 75sqm to cool. I have the same sized space in my house, also the ground floor of two, which has a total of 60,000 BTU between two AC's: a 24,000 BTU + and 36,000 BTU - and even on > 40c days they do the job without any strain. I wouldn't want any less though, but I certainly don't need any more either.

Thank you! It hadn't crossed my mind that I didn't need to worry about the cold air from aircon rising up the stairs!

The downstairs area (now that I've remembered to add in the part of the kitchen that sticks out from the living room and computer room....) is approx 7 X 6.5 X 3, which is roughly 136 sqm?

But I come back to my original question, is it more cost effective to have one 12.500 BTU aircon that cools the area I need (but is running flat out as it tries/fails to cool the rest of the area) or to have a larger (27,000 BTU?) unit that will cost more per hour, but not be running flat out all the time?

[IMHO]

You can't just cool down a part of a space - for part if it to be cool, all of it needs to be cool.

The upstairs landing doesn't factor into to it - if the room is downstairs and the AC's downstairs, that's where the cold is also staying.

So basically, you have a downstairs room of 75sqm to cool. I have the same sized space in my house, also the ground floor of two, which has a total of 60,000 BTU between two AC's: a 24,000 BTU + and 36,000 BTU - and even on > 40c days they do the job without any strain. I wouldn't want any less though, but I certainly don't need any more either.

Thank you! It hadn't crossed my mind that I didn't need to worry about the cold air from aircon rising up the stairs!

The downstairs area (now that I've remembered to add in the part of the kitchen that sticks out from the living room and computer room....) is approx 7 X 6.5 X 3, which is roughly 136 sqm?

But I come back to my original question, is it more cost effective to have one 12.500 BTU aircon that cools the area I need (but is running flat out as it tries/fails to cool the rest of the area) or to have a larger (27,000 BTU?) unit that will cost more per hour, but not be running flat out all the time?

First of all, you are calculating cubic meters, not square meters. Forget about the ceiling height - 3M is considered standard. With that in mind, 7x6.5 = 45sqm. That's a lot smaller than what we understood earlier (5x15M=75sqm) - so clarity on that would help

Even in the smaller of the two - 45sqm - a 27K BTU will still run flat out during the day (less duty cycle at night though) because it's still under-sized for the total area.

The bottom line is, the more BTU you use, the more it's going to cost. If the 12K BTU unit is keeping you cool enough where you want it to, I'd say just stick with it.

As a guide, it costs me around 20 Baht/hour in electricity to cool my 75sqm home theatre room during the day, dropping to as low as 10 Baht/hour at night. Both AC's are 3rd generation R-32 Daikin inverters (i.e. as about efficient as AC's get).

Edited May 1, 2016 by IMHO

[dick dasterdly]

From my experience Thai air-conditioning tradesmen aren't as dumb as TVF experts pretend they are.

Trust your local technician, he is trying to help.

You misunderstand me, I'm not implying that the technician who came to my house is dumb! I was dumb giving the measurements to the store, rather than working it out for myself.

He told me that I needed a 70,000 BTU aircon to cover the entire open plan area and also suggested that I install another aircon in the living room. When I got round to googling BTU based on area, he was absolutely right - even more so now that I've read another poster's comments who pointed out that cold air will not go upstairs, so another similar sized unit fitted in the living room would work pretty well downstairs (his recommendation).

But I don't need to cool the entire downstairs area - which is why I'm still wondering whether its better to have one unit that keeps the small area in which I'm interested, cool (but is working flat out for hours), or whether its more economical to use an air con unit(s) that cost more per hour, but won't be working flat out all the time.

The aircon in the bedroom at nights already adds 1,500 bht p.m. (approx) to my elec bill, and my normal elec bill is close to 4,000 p.m. - which is why I'm concerned about the most economical option for when I need to use downstairs aircon during the day.

[lopburi3]

I suspect he said you needed to cool about 70 square meters based on your post of area being 15x5sm - but now you say area is actually 7x6.5 which would be 45 square meters. The 3 meters high is not used to find square meters.

[IMHO]

The aircon in the bedroom at nights already adds 1,500 bht p.m. (approx) to my elec bill, and my normal elec bill is close to 4,000 p.m. - which is why I'm concerned about the most economical option for when I need to use downstairs aircon during the day.

I had some house guests over Songkran for a couple of weeks, and the HT room AC's got used more than they normally would - from 2/7, to about 20/7. That added about 4,000 Baht to my electricity bill alone

[sipi]

From my experience Thai air-conditioning tradesmen aren't as dumb as TVF experts pretend they are.

Trust your local technician, he is trying to help.

You misunderstand me, I'm not implying that the technician who came to my house is dumb! I was dumb giving the measurements to the store, rather than working it out for myself.

He told me that I needed a 70,000 BTU aircon to cover the entire open plan area and also suggested that I install another aircon in the living room. When I got round to googling BTU based on area, he was absolutely right - even more so now that I've read another poster's comments who pointed out that cold air will not go upstairs, so another similar sized unit fitted in the living room would work pretty well downstairs (his recommendation).

But I don't need to cool the entire downstairs area - which is why I'm still wondering whether its better to have one unit that keeps the small area in which I'm interested, cool (but is working flat out for hours), or whether its more economical to use an air con unit(s) that cost more per hour, but won't be working flat out all the time.

The aircon in the bedroom at nights already adds 1,500 bht p.m. (approx) to my elec bill, and my normal elec bill is close to 4,000 p.m. - which is why I'm concerned about the most economical option for when I need to use downstairs aircon during the day.

Yes Dick, I agree.

What I meant to say was, from my experience it is best to consult a technician on-site and take his advice. They are trained to help.

[dick dasterdly]

You can't just cool down a part of a space - for part if it to be cool, all of it needs to be cool.

The upstairs landing doesn't factor into to it - if the room is downstairs and the AC's downstairs, that's where the cold is also staying.

So basically, you have a downstairs room of 75sqm to cool. I have the same sized space in my house, also the ground floor of two, which has a total of 60,000 BTU between two AC's: a 24,000 BTU + and 36,000 BTU - and even on > 40c days they do the job without any strain. I wouldn't want any less though, but I certainly don't need any more either.

Thank you! It hadn't crossed my mind that I didn't need to worry about the cold air from aircon rising up the stairs!

The downstairs area (now that I've remembered to add in the part of the kitchen that sticks out from the living room and computer room....) is approx 7 X 6.5 X 3, which is roughly 136 sqm?

But I come back to my original question, is it more cost effective to have one 12.500 BTU aircon that cools the area I need (but is running flat out as it tries/fails to cool the rest of the area) or to have a larger (27,000 BTU?) unit that will cost more per hour, but not be running flat out all the time?

First of all, you are calculating cubic meters, not square meters. Forget about the ceiling height - 3M is considered standard. With that in mind, 7x6.5 = 45sqm. That's a lot smaller than what we understood earlier (5x15M=75sqm) - so clarity on that would help

Even in the smaller of the two - 45sqm - a 27K BTU will still run flat out during the day (less duty cycle at night though) because it's still under-sized for the total area.

The bottom line is, the more BTU you use, the more it's going to cost. If the 12K BTU unit is keeping you cool enough where you want it to, I'd say just stick with it.

As a guide, it costs me around 20 Baht/hour in electricity to cool my 75sqm home theatre room during the day, dropping to as low as 10 Baht/hour at night. Both AC's are 3rd generation R-32 Daikin inverters (i.e. as about efficient as AC's get).

My mistake as I'm not technically minded, but as all google calculators used L X W X H, I used this with the latest calculation (which excluded the stairs and upstairs landing area as per your good advice). And that advice is also why the dimensions have changed plus, when measuring windows, realising that I'd missed the bit of the kitchen that sticks out from the living room/computer room.

I gather inveters are only efficient if they aren't running at full power all the time?

Fortunately, I only need downstairs aircon when its v hot (above 33C).

So in short, its more economical to use a 12,000 BTU aircon that will cool the small area that needs to be cooled - even though it will be running at full strength for about 10 hours?

[IMHO]

You can't just cool down a part of a space - for part if it to be cool, all of it needs to be cool.

The upstairs landing doesn't factor into to it - if the room is downstairs and the AC's downstairs, that's where the cold is also staying.

So basically, you have a downstairs room of 75sqm to cool. I have the same sized space in my house, also the ground floor of two, which has a total of 60,000 BTU between two AC's: a 24,000 BTU + and 36,000 BTU - and even on > 40c days they do the job without any strain. I wouldn't want any less though, but I certainly don't need any more either.

Thank you! It hadn't crossed my mind that I didn't need to worry about the cold air from aircon rising up the stairs!

The downstairs area (now that I've remembered to add in the part of the kitchen that sticks out from the living room and computer room....) is approx 7 X 6.5 X 3, which is roughly 136 sqm?

But I come back to my original question, is it more cost effective to have one 12.500 BTU aircon that cools the area I need (but is running flat out as it tries/fails to cool the rest of the area) or to have a larger (27,000 BTU?) unit that will cost more per hour, but not be running flat out all the time?

First of all, you are calculating cubic meters, not square meters. Forget about the ceiling height - 3M is considered standard. With that in mind, 7x6.5 = 45sqm. That's a lot smaller than what we understood earlier (5x15M=75sqm) - so clarity on that would help

Even in the smaller of the two - 45sqm - a 27K BTU will still run flat out during the day (less duty cycle at night though) because it's still under-sized for the total area.

The bottom line is, the more BTU you use, the more it's going to cost. If the 12K BTU unit is keeping you cool enough where you want it to, I'd say just stick with it.

As a guide, it costs me around 20 Baht/hour in electricity to cool my 75sqm home theatre room during the day, dropping to as low as 10 Baht/hour at night. Both AC's are 3rd generation R-32 Daikin inverters (i.e. as about efficient as AC's get).

My mistake as I'm not technically minded, but as all google calculators used L X W X H, I used this with the latest calculation (which excluded the stairs and upstairs landing area as per your good advice). And that advice is also why the dimensions have changed plus, when measuring windows, realising that I'd missed the bit of the kitchen that sticks out from the living room/computer room.

I gather inveters are only efficient if they aren't running at full power all the time?

Fortunately, I only need downstairs aircon when its v hot (above 33C).

So in short, its more economical to use a 12,000 BTU aircon that will cool the small area that needs to be cooled - even though it will be running at full strength for about 10 hours?

Correct - inverters only save money when the cooling power needed is something less than 100% capacity.

Also correct that your 12K BTU aircon will be cheaper to run than anything bigger - even if it is optimally sized for the space, and has fancy refrigerants and an inverter. There's simply no cheap way to cool a space that big.

[dick dasterdly]

Thanks IMHO, that's all I needed to know. I just vaguely hoped that a larger unit might work out cheaper in the long-run as it would rest every now and again.

[casualbiker]

Maybe look at getting an additional 18btu unit.. You also haven't mentioned what temperature you want to sustain 27 is going to be easier than 21 for example.. I can recommend Haier 18btu aircons for a larger room.. They aren't the quietest but OK.. But it works efficiently and is relatively cheap to buy.. https://www.kaidee.com/product-112846639