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Aircon sizing for bedroom advice?

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I am considering replacing a more than 10 year old Panasonic conventional AC, which is a 13k BTU, with an Inverter model, probably either Daikin or Mitsu. and need some advice.

 

Using the Daikin site however https://www.daikin.co.th/en/service-btu-calculation/# I have had conflicting results when sticking in the rough sizes.

Currently for a 20sq m room it says I need their 17.7k BTU inverter.......When I tried this originally I am sure it came up with 14.3k BTU versions and a couple of times it has come up with "room is too big contact......" which makes me question the tool.

 

Actual room size is 19.53sq m excluding space taken up with fitted wardrobes - should I include this space in the calculation?

Room is second floor directly under the roof with a double glazed french door which gets sun from mid afternoon but curtains with silver lining are closed most of the time. Ceiling height is mainly 2.7m

 

In another thread (for a 26sq m room) @Crossy you said -

Quote

Conventional Thai wisdom would size at  15,000-18,000 BTU (600-700BTU per m2) for that size room, and that would be somewhat over-size.

And @sometimewoodworker

Quote

Completely with you on that, our old bedroom with virtually no insulation was comfortable with a conventional AC and was about 500 BTU per mit was never stretched.

With current unit (but old though regularly cleaned) set at 26 it takes a long time before it seems to cool/extract humidity to be really comfortable when going to bed. Only recently with the temperatures being lower have I noticed it cycling off/on a few times. 

 

Using 700 per sq m I could get away with the smaller unit. Any advice welcome  :smile:

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Over sizing with a non inverter is an extremely bad idea, however since you will be getting an inverter that is much less of a concern. So I would go with 700 and get something slightly bigger rather than slightly smaller.

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20 sm is not a large room but if no insulation in ceiling (you do have a ceiling?) and directly below roof it may indeed need more than what I use.

 

My bedroom is about 26sm and only need 9k btu to keep comfortable.  But for us comfort is more like 28 rather than 26 (gets higher with every decade here).  One thing to take into account is inverter will be blowing cold air all the time so it will likely feel colder and you may need to prevent direct air flow unless sleeping under blankets.

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41 minutes ago, sometimewoodworker said:

Over sizing with a non inverter is an extremely bad idea, however since you will be getting an inverter that is much less of a concern. So I would go with 700 and get something slightly bigger rather than slightly smaller.

So you reckon the Daikin calculation for a 17k BTU is too much?

At 700 would only need the 14.3.

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29 minutes ago, lopburi3 said:

you do have a ceiling?

yes :biggrin: - but can only guess if any insulation between that and the roof. Based on the re-modelling of some of the other houses in the village there should be some but the house was built 2006/7.

 

Unfortunately the only real installation location (without an awful lot of changes) is where it is currently which is directly over the bed.

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36 minutes ago, topt said:

Unfortunately the only real installation location (without an awful lot of changes) is where it is currently which is directly over the bed.

That might be the best place as you can direct flow across room rather than at you, at least with Daikin very little air flow directly below if you lock vane in up position.

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1 hour ago, topt said:

So you reckon the Daikin calculation for a 17k BTU is too much?

At 700 would only need the 14.3.

That would be my choice. Though I don't see any model at Top Cool that is exactly that size.

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1 hour ago, topt said:

So you reckon the Daikin calculation for a 17k BTU is too much?

At 700 would only need the 14.3.

That is big for a small room , Have tried several other calculators?

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Thai stores always overquote on BTU for square metres. I was quoted 40K BTU for a 36 sqm apartment. Complete BS.

10 - 12K BTU for 20 sqm should be quite adequate.

 

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1 hour ago, madmen said:

That is big for a small room , Have tried several other calculators?

Yes but......

Carrier Thailand - 19k BTU.........

A US site about 7k BTU

Another couple of sites anything from 5 - 25k BTU

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1 hour ago, sometimewoodworker said:

That would be my choice. Though I don't see any model at Top Cool that is exactly that size.

 

1 hour ago, Lacessit said:

Thai stores always overquote on BTU for square metres. I was quoted 40K BTU for a 36 sqm apartment. Complete BS.

10 - 12K BTU for 20 sqm should be quite adequate.

 

Daikin in their Super Smile and Super Smart inverter range have 11.9k, 14.3k and 17.7k BTU (and smaller and bigger of course). Not looked at Mitsu yet.

 

If I could get away with the 11.9 it would be good.......but looking like the 14.3 to be safe.....

 

No-one has commented but should the fitted wardrobe space be included as that is about another 2.5/3 sq m on top of the 19.53.

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4 minutes ago, topt said:

 

Daikin in their Super Smile and Super Smart inverter range have 11.9k, 14.3k and 17.7k BTU (and smaller and bigger of course). Not looked at Mitsu yet.

 

If I could get away with the 11.9 it would be good.......but looking like the 14.3 to be safe.....

 

No-one has commented but should the fitted wardrobe space be included as that is about another 2.5/3 sq m on top of the 19.53.

one thing you haven't considered in your calculations is how hot the room gets in the day, or how much residual heat is stored in the walls.

I live in a ground floor condo and the walls get almost no direct sunlight, so a 9000 BTU is more than enough for 18 m2.

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I don't know if this helps.

The two bedrooms we use are both 18sm. I have just fitted a new LG NOT inverter 11.Th BTU in one and it works fine. Once cool a few min: it just stays on tick over. The other bedroom has a 11.74th BTU Saijo Denki also non inverter. Used every day for the last 13 years without any problems. We do have our ceilings lined though.

You say yours is 20sm so would suggest 12/13th max.   

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2 hours ago, topt said:

Daikin in their Super Smile and Super Smart inverter range have 11.9k, 14.3k and 17.7k BTU

That exact range is not on the Thai web page I linked to above, there is an 11.9 and 17.7 but no 14.3. The only 14.x is a 14.4 in a different range. So either the website is out of date or your brochure is listing an old model, or they have different models for English speakers 😉 

 

The model numbers are more helpful for tracking down the exact unit. 

Edited by sometimewoodworker

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8 hours ago, sometimewoodworker said:

That exact range is not on the Thai web page I linked to above, there is an 11.9 and 17.7 but no 14.3. The only 14.x is a 14.4 in a different range. So either the website is out of date or your brochure is listing an old model, or they have different models for English speakers 😉 

 

The model numbers are more helpful for tracking down the exact unit. 

Yes I was looking at FTKC15TV2S and FTKM15TV2S from the Daikin web site.

From your link -

FTKM15NV2S    15,000  220  31,900   3,190 

 29,900 

 

From Daikin Thailand English site - https://www.daikin.co.th/en/product/residential-en/room-air-en/

Specification Unit FTKM15SV2S
Cooling Capacity BTU/h 14,300 (4,100-16,400)
Power Consumption W 1,105 (185-1,630)
SEER BTU/W-h 20.7

 

However they all seem a bit more expensive than I expected! :sad:

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