Air Conditioner Sizing

[lanwithatz]

Help!  I have been getting a lot of conflicting advice and reading on the subject.  We just built a house in Khon Kaen and now need to pick wall mounted air conditioners.  The room in question has a large south facing window and door (I would have built it in reverse in hind sight, oh well.).  It measures 4mx7m with 3.8m ceilings.  Some sources say 18k BTU and others 24KBTU.  We plan to have it running most of the day until bedtime, with little to no cooking.  Any of your real world experience would be appreciated.  Thank you!

I attached a couple pics of the room and front of house where the room is in the center.

[mfd101]

From our experience I would suggest good-quality heavy curtains on the windows/doors where the sun shines in.

 

As to a/cs, bigger run at moderate speed is going to last longer than smaller run at faster speed. Daikin are good. Regular cleaning and maintenance essential.

[JBChiangRai]

It's a long room, I would fit 2 of 12,000 BTU Inverter Air Cons, one at each end.

 

Our business has fitted dozens of air cons of many different makes, our favourite is TCL sourced from Lazada and fitted by our own contractor.  The only ones we don't like are LG (noisy) and Daikin (go yellow and not properly designed to stop geckos destroying logic boards).

 

I would try and do something outside to stop the sun hitting your single thickness block walls and windows.  Your walls are going to absorb heat and radiate it into the room all afternoon/evening.

Edited February 2 by JBChiangRai
Spellong

[Crossy]

Nice looking home.

 

I agree with @JBChiangRai says, 2 x 12k inverters (you can run just one in cool season).

 

We have a similar sized/shaped room with one 24k in the centre (outside space constraints for the compressor). It needs a stand fan just to move the cool air around.

 

Definitely get some shade plants to reduce the daytime heat load.

 

[lanwithatz]

10 minutes ago, JBChiangRai said:

It's a long room, I would fit 2 of 12,000 BTU Inverter Air Cons, one at each end.

 

Our business has fitted dozens of air cons of many different makes, our favourite is TCL sourced from Lazada and fitted by our own contractor.  The only ones we don't like are LG (noisy) and Daikin (go yellow and not properly designed to stop geckos destroying logic boards).

 

I would try and do something outside to stop the sun hitting your single thickness block walls and windows.  Your walls are going to absorb heat and radiate it into the room all afternoon/evening.

Unfortunately it was only wired for one unit facing a less than optimal direction.  Pick below shows its location in red.

[OneMoreFarang]

My real-world experience suggest 24k BTU.

 

About the windows: I have a south facing wall which is 90% window. This in in my case no problem, the sun is not shining directly into those windows.

It seems in Thailand the west facing windows (and maybe east) are the problem. There the sun shines right into the window in the (late) afternoon.

[Crossy]

3 minutes ago, lanwithatz said:

Unfortunately it was only wired for one unit facing a less than optimal direction.  Pick below shows its location in red.

 

In that case one 24k as close to the centre of the long axis as possible.

[OneMoreFarang]

38 minutes ago, JBChiangRai said:

It's a long room, I would fit 2 of 12,000 BTU Inverter Air Cons, one at each end.

According to many "experts" that is bad advice.

 

https://gharpedia.com/blog/best-location-wall-mounted-air-conditioning-unit/

 

[OneMoreFarang]

7 minutes ago, lanwithatz said:

Unfortunately it was only wired for one unit facing a less than optimal direction.  Pick below shows its location in red.

With some ACs, i.e. from Daikin, they have a sensor build in.

The user can select if the AC should spread the cold air to everywhere, or only concentrated on one human (sensor) or away from that one human.

[Crossy]

8 minutes ago, OneMoreFarang said:

According to many "experts" that is bad advice.

 

Remember "x" is an unknown (or "ex" is a has-been) and a "spurt" is a drip under pressure

 

My job description is "specialist" 🙂 

[mran66]

23 minutes ago, lanwithatz said:

Unfortunately it was only wired for one unit facing a less than optimal direction.  Pick below shows its location in red.

 

Another vote for two smaller units for large space. Not difficult to pull wires from breaker box above the ceiling to any area, that's what I have done.

 

Also, 12kBTU can even run from a socket as long as no higher power kitchen equipment connected to same breaker cirquit...

[JBChiangRai]

45 minutes ago, OneMoreFarang said:

According to many "experts" that is bad advice.

 

https://gharpedia.com/blog/best-location-wall-mounted-air-conditioning-unit/

 

 

Sorry I disagree with your experts, I don't see anything wrong with either of those placements, it would come to usage zones & furniture placement, but all things being equal, I would still place them at either end.  I think fitting over 100 A/C units in houses we have built makes me a specialist too.

 

I try to avoid putting units over tall windows, there's usually insufficient space when you allow for curtains.

[JBChiangRai]

25 minutes ago, mran66 said:

 

Another vote for two smaller units for large space. Not difficult to pull wires from breaker box above the ceiling to any area, that's what I have done.

 

Also, 12kBTU can even run from a socket as long as no higher power kitchen equipment connected to same breaker cirquit...

 

I agree, I would pull another cable. 

[RayWright]

Having designed Computer Rooms / Data Centers, golden rule was never to have the AirCon units facing each other, as the airflow across the room is effected, and the Temperature sensors in the units will shut the units down quicker, so you'll end up with a stop-start system, rather than a constantly running / comfort cooling system.

 

Quick question. Any reason why AirCon wasn't included in the original building design? Impact on aesthetics, electrical distribution, outdoor condenser placement etc. 

[lanwithatz]

51 minutes ago, JBChiangRai said:

 

Sorry I disagree with your experts, I don't see anything wrong with either of those placements, it would come to usage zones & furniture placement, but all things being equal, I would still place them at either end.  I think fitting over 100 A/C units in houses we have built makes me a specialist too.

 

I try to avoid putting units over tall windows, there's usually insufficient space when you allow for curtains.

Would you have any tips on placement for two units? I'm not sure if we can get to the exterior via the sides of the room.  the back of the room where the current line is  has a large window above the sink area where nothing above will fit.  Of course going out the front would be ugly as hell and not pass the wife test.IMG_6532.HEIC

IMG_6527.HEIC IMG_6532.HEIC

[lanwithatz]

4 minutes ago, RayWright said:

Having designed Computer Rooms / Data Centers, golden rule was never to have the AirCon units facing each other, as the airflow across the room is effected, and the Temperature sensors in the units will shut the units down quicker, so you'll end up with a stop-start system, rather than a constantly running / comfort cooling system.

 

Quick question. Any reason why AirCon wasn't included in the original building design? Impact on aesthetics, electrical distribution, outdoor condenser placement etc. 

the placement was built into the design but the units and install were not included.  maybe I overlooked the placement or maybe they made change I didn't notice.  Its been a while since we started and it isn't a major focus of mine.  I found it strange what the contractor was willing to do and not.  I've learned a lot should I have another build someday.

[JBChiangRai]

Looking at your walls and required pipework, I would put one where you were planning and another diagonally opposite on the opposite facing wall with the compressor either outside at the front (if you live with it) or take the pipes through the shower room and put the compressor on the other side of that shower room.

 

Alternatively, fit a 24,000 BTU cassette unit in the middle of the room.

[JBChiangRai]

15 minutes ago, RayWright said:

Having designed Computer Rooms / Data Centers, golden rule was never to have the AirCon units facing each other, as the airflow across the room is effected, and the Temperature sensors in the units will shut the units down quicker, so you'll end up with a stop-start system, rather than a constantly running / comfort cooling system.

 

Quick question. Any reason why AirCon wasn't included in the original building design? Impact on aesthetics, electrical distribution, outdoor condenser placement etc. 

 

I have a similar background (CIO) and I agree with you about having large A/C units facing each other in a datacenter where airflow is always at maximum, however in a home environment with small 12,000 BTU units, it's not going to happen across 7m, you are going to get local cooling at each end of the room.

 

I value silence very highly, most Inverter A/C have a silent mode and often the next setting up is pretty silent too and two units are going to be quieter than one unit, also one single unit at one end of the room is going to leave the other end of the room warm.

[Arindos]

You may also be better off investing in wooden blinds similar to those found in southern Europe.

Edited February 2 by Arindos

[Will B Good]

1 minute ago, Arindos said:

You may also be better off investing in wooden blinds similar to those found in southern Europe.

Plastic might be a better option over here....more expensive in the short term.

[OneMoreFarang]

1 hour ago, JBChiangRai said:

 

Sorry I disagree with your experts, I don't see anything wrong with either of those placements, it would come to usage zones & furniture placement, but all things being equal, I would still place them at either end.  I think fitting over 100 A/C units in houses we have built makes me a specialist too.

 

I try to avoid putting units over tall windows, there's usually insufficient space when you allow for curtains.

Ok, you fitted 96 more ACs then I did - or maybe more.

 

Before I did that, I looked at many articles about that issue on the internet. And above is what I found. I remember there was also some explanation why it shouldn't be done with an AC on each side of the room facing each other.

I have too little experience to know. I just share what I read many times. 

[Crossy]

19 minutes ago, lanwithatz said:

I've learned a lot should I have another build someday.

 

We built once, once was enough!!!

 

We are both too long in the tooth for the hassle.

[JBChiangRai]

I would extend your roof trellis at the front to cover the whole front and then plant climbing plants to make a canopy.

[JBChiangRai]

2 minutes ago, OneMoreFarang said:

Ok, you fitted 96 more ACs then I did - or maybe more.

 

Before I did that, I looked at many articles about that issue on the internet. And above is what I found. I remember there was also some explanation why it shouldn't be done with an AC on each side of the room facing each other.

I have too little experience to know. I just share what I read many times. 

 

Opposite ends of the room depends on the distance and power of the units, with small units and a decent enough distance you're not going to get interference, but in general I would agree with you, if in doubt, don't.

[Crossy]

17 minutes ago, JBChiangRai said:

I would extend your roof trellis at the front to cover the whole front and then plant climbing plants to make a canopy.

 

Yeah, that area is going to be an oven, shading it would make a nice "sitting-out" area, why waste the lovely weather here?

 

Climbers like bougainvillea are happy in containers, grow fast and provide great shade.

 

EDIT: - Ours need a haircut (gardener comes on Sunday), but you get the general idea.

 

[Denim]

3 hours ago, mfd101 said:

From our experience I would suggest good-quality heavy curtains on the windows/doors where the sun shines in.

 

Absolutely. When choosing an air con unit there is more to consider than just room size. In the hot season you could easily fry an egg on our windows ( if they were not vertical )

 

If you can somehow get the outside of the windows shaded in some way it makes the work of the air con so much easier.

[JimTripper]

Why no ceiling fans?

[spidermike007]

32 minutes ago, JBChiangRai said:

I would extend your roof trellis at the front to cover the whole front and then plant climbing plants to make a canopy.

Exactly, anything you can do to keep the sun off the walls and windows is going to have a dramatic effect on how cool the room is. 

 

Also you made no mention of whether or not you've insulated the attic, that's a huge factor and makes an enormous difference. In addition to that exhaust fans in the attic will cool down your attic temperature dramatically, at minimal annual cost. 

[lanwithatz]

Thanks everyone.  You all have been very helpful.  I would have undersized without your help.

[Crossy]

6 minutes ago, spidermike007 said:

Also you made no mention of whether or not you've insulated the attic, that's a huge factor and makes an enormous difference.

 

Those nice flat areas would be ideal for solar, the additional shading of the roof would reduce heat-gain via the roof significantly.

 

As a bonus you get free electricity 🙂