Aircon Advice

[ubonrthai]

I need aircon for the 1st floor of a townhouse. Inside measures 3.6m high, 4.1m wide, 14m deep. All glass front and a small door in the back. Concrete walls and neighbors on each side. I'm ok with wall fans much of the year and it won't be too often that I want the entire room cooled down. I had considered one of those rolling floor units but previous threads on TV about these are not favorable and my hunch is they are energy hungry pieces of junk. That being said, I plan to get a wall mounted AC.

1. How many BTU do you think I should get?

2. Worth the expense for an inverter? Guessing it would take a lot to cool the entire room before the savings of an inverter are worth it.

3. My favorite location for the wall mounted AC is pretty close to the ceiling. Is that too high in a 3.6m room?

Appreciate the ideas.

Edited April 3, 2015 by ubonrthai

[trogers]

What faces west? Space to be cooled opened into the stairwell?

[IMHO]

That is a reasonably large area to cool - it's all one big open space, or separate rooms?

1. I understand that fans normally get you by - does that also mean that you might be happy with a higher than normal AC temp - say 30c instead of 25c?

2. Just how hot does it get when fans don't get you by (jnside and outside)?

3. What direction does the glass frontage face? (compass direction, that is) Would I be right is guessing North-ish? You're posting this during the summer solstice, and the sun has now been coming from the North for about a week and a half

Edited April 3, 2015 by IMHO

[ubonrthai]

We are now blocking off the back area where the steps are with an aluminum/glass wall so depth of room is now 9.5m. Front doors face South. Called multiple places. Most recommend 2 18,000btu units or 2 24,000btu units. I'd rather have one big one. 36,000btu

[Pib]

Plenty of A/C size calculators on the web....google is your friend. But "one" 18K BTU should do the job...or go with one approx 22-24K BTU. I cool an area larger than what you are talking about to 26C day and night with one 18K BTU fixed/constant speed A/C...I'm in Bangkok and live in a two story house...the A/C is mounted approx in the middle of the area and up on the wall about 20cm below ceiling....of course you can direct the A/C output down and cool air does sink since it's heavier than hot air...or is hot air lighter than cool air.

By fixed/constant speed I mean the typical type of A/C where the compressor is either on or off; not an Inverter A/C were the compressor speed can vary to meet cooling requirements and usually lower your cooling/electricity cost as long as the Inverter A/C is not undersized and has to run at its upper capacity to adequately cool the area. Additionally, with an Inverter A/C although it will come with a nominal rating of say 18K BTU it will actually have a BTU capability of up to around 20K BTU and down to around 3K BTU as it varies its speed to meet cooling requirements...it may initially start off at say 20K BTU with a hot room and as it cools down the areai the compressor speed/BTU capability will taper off....lower the BTU output...decease your electric bill And a 24K BTU Inverter A/C would have a BTU range from approx 5K BTU to 27K BTU.

Here's a link to one of many A/C calculators out there on the web. Link. I ran it for a 4m x 4m x 14m room, normal insulation, and a temp drop of 15C from the outside temp (a 15C drop is probably overkill except for the hottest months of the year)....like from 41C (hot) to 26C (comfortable for most). Below are snapshots of the results for a 15C and 10C temp drops.

15C Temp Drop

10C Temp Drop

Personally I would buy an Inverter A/C...they are pricier upfront and usually to repair than a typical fixed speed A/C, but A/Cs are pretty reliable now days and after 2 to 3 years of use that extra cost will be offset by lower electricity bills if you use the A/C a good amount each year. When I bought my home new about 7 years ago the house came with the fixed speed A/Cs installed...but at the point any of the main A/Cs like the 18K I mentioned breaks and is not economically repairable, I will replace it with a 18K or 22-24K BTU Inverter A/C.

Edited April 4, 2015 by Pib

[IMHO]

We are now blocking off the back area where the steps are with an aluminum/glass wall so depth of room is now 9.5m. Front doors face South. Called multiple places. Most recommend 2 18,000btu units or 2 24,000btu units. I'd rather have one big one. 36,000btu

OK, so now we have 9.5 x 4.1 = 39sqm

In this space, 36K BTU will give you over 900 BTU/sqm - which is almost enough cooling power for a gym, so shouldn't let you down in a house

My guess why you're hitting resistance on the single unit idea just because there's only one brand that manufacture a 36K BTU wall-mount - Saijo Denki - if they don't sell Saijo Denki, they're either going to be suggesting dual AC's (nothing wrong with that if it's doable for you) or a commercial ceiling mounted type, which are unsightly and noisy.

There's nothing wrong with oversizing up to 1000 BTU/sqm (but plenty wrong with undersizing) - but you would probably still want to consider an inverter unit, so you're not wasting power on days where the full 36K BTU just isn't needed.

Edited April 4, 2015 by IMHO

[KittenKong]

The thing I really like about inverter models is that you dont get the constant switching from freezing cold air to completely unchilled air that you get with the regular sort.

The inverter models produce a nice constant stream of air that is neither too hot nor too cold, and this varies slowly as the requirements of the room alter.

Much more comfortable, and quieter too. The electricity savings are a bonus.

[cvs04]

I found when I was looking for AC Units in Ubon to cool a big shophouse area like this all the AC shops quoted double what the energy websites quoted. I think the formula they use is somewhat biased in favour of profit.

Try what the website BTU calculators tell you first then increase if necessary, ou can always add another unit later on. Professional AC guys told me if you have too many BTU it does cool the room quicker but the air doesn't get conditioned properly and you end up with condensation. You can see this sometimes in 7/11's, they tend to go a bit overboard in those places.

Edited April 5, 2015 by cvs04

[Pib]

Try what the website BTU calculators tell you first then increase if necessary, ou can always add another unit later on. Professional AC guys told me if you have too many BTU it does cool the room quicker but the air doesn't get conditioned properly and you end up with condensation. You can see this sometimes in 7/11's, they tend to go a bit overboard in those places.

That will indeed happen if the A/C is too big, especially if a fixed/constant speed A/C where the compressor is either on or off....and when it cuts off it won't cut back on again until the temperature rises 1 or 2C above our desired setting....then it cuts on and keeps running until it pulls the temp down to a little below your desired temp like say a desired temp of 26C. This can sometimes cause some noticeable temp swings depending on the area being cooled. Now there is plenty of room for interpretation of how much "too big" is as it can vary greatly based on the area your are cooling, outside environment, insulation effect, etc. Plus larger A/Cs like 18K or 24K are louder than smaller A/Cs like 12K and below, whether fixed speed or inverter.

But with an Inverter A/C there is less change of getting one too big because of how an Inverter A/C can vary its BTU cooling capacity from around 10% above its nominal rating to many times below its nominal rating. Like say an Inverter A/C with a nominal rating of 18K BTU where the max BTU capability could go up to around 20K and down to around 3K BTU. I'm looking at a Hitcahi Air Conditioner Brochure right now and whether the nominal rating of their Invertor A/C is 10, 13, or 18 BTU they can all go down to only 3K BTU....and their 24K Invertor A/C can go down to around 5K BTU.

So, getting an Inverter A/C that is oversized for you room is harder to achieve since it can downshift its' BTU capability significantly...but that don't mean to go out and buy a big BTU Inverter A/C just to play it safe as you should still try to approx the size you need for your room to reduce you initial cost outlay and to get the best electrical efficiency from the unit. No use buying a horse to pull your wagon if a pony can do the job.

Now, a person can still mess up in getting an Inverter A/C that is too small....because if it's too small it will not ever be able to downshift in its BTU usage and continue to run a full speed which means your Invertor A/C is pretty been turned into a fixed/constant speed A/C which runs at full BTU capacity when on. Then you get no electricity savings because an Inverter A/C and Fixed Speed A/C of identical nominal rating pull fairly close amperage/power. For example, looking at that Hitachi brochure again their 24K BTU inverter A/C pulls 9.4 amps at its nominal BTU output and their 24K BTU Fixed speed A/C pulls 9.1 amps. An inverter A/C energy savings comes from being able to downshift its BTU usage; if it can't because its undersized you won't save any electricity over a same size Fixed speed A/C.

In closing, take with a grain of salt energy savings estimates in many Inverter A/C brochures because those max savings are usually only obtained with just the right conditions/in a laboratory environment. Inverter A/Cs can definitely give very significant energy savings when properly sized but it may be less than the manufacturer's advertisement for many different environmental and sizing reasons. Also, when a lot of people replace their fixed speed A/C it is usually because it is not cooling very good anymore and using more electricity than when new....maybe because of a mechanical/electrical problem or it really just needs serving which the owners have rarely down......then when they install that new properly size Inverter A/C they see a significant energy savings and praise the A/C gods. But in some cases they could have got a lot of their energy savings back by just having their fixed speed A/C properly serviced on a periodic basis (a.k.a.., keeping the inside and outside unit clean and topped-up with freon).

Edited April 5, 2015 by Pib

[dddave]

Just my own recent experience. (BTW, another thanks to all the TV members who helped answer my questions on this same topic 5 months ago)

I have a 50 s/m (inside space) single room, one south wall. I had a very old (15 to 20+ year old) 25K unit. My elect bill cool season normally about B3000, hot season; B5 to 6000.

Last fall, the compressor (outside) unit died. AC shop on my soi who I had used in the past recommended new, quoting B40,000. I asked about used and against his advice had them find and install a used replacement compressor, cost me B6000 all in.

BAD idea!!!

Noisy as a locomotive. Crew came 3 times to find ways to quiet it as neighbors were justifiably complaining about the noise at night. Also cycled on and off frequently. Then the bill came for November, it's first full month, normally a cooler period with a B3 to 4000 bill. New bill an unbelievable 7500Baht!!! Needless to say, I totally freaked out.

Once I stopped hyperventilating, I had to admit to myself that I had made a truly dumb move ignoring good advice and going with the used compressor. It was clearly to old and inefficient and nothing was going to make it work any better. Time to cut my losses, get rid of it and get a new one.

I did a lot of research online and posted some questions here which got a lot of helpful responses. Most of the AC info online about the common 2 piece systems used in Thailand was Australia based, not much specific to Thailand in English. I did learn enough that I knew if I could buy a unit with an "Inverter" for an affordable price, that was the way to go.

Most appliance department AC salespeople are not very helpful and finding ones with decent English skills not easy. Most would go to their charts and push 30,000 BTU units with inverter types pushing B45,000+++.

With help from this forum, I decided I did not need to go that high. Coincidentally, POWER MALL at Siam Paragon was having it's annual clearance sale and I was able to find a well reviewed SAMSUNG unit, 21,000 BTU with inverter for B22,000 installed. I had done a lot of shopping and that was an amazingly low price for an inverter unit and Samsung is a reasonably reliable mainline manufacturer. It was fully installed and operating within 7 days of purchase.

I have now had it almost 5 months and I just got my power bill for March 16-April 16: B2600 for a very hot 4 weeks, way less than I used to pay, even in cool season. It is on all night and probably half the day, sometimes all day. I run it at 25 degrees and move the air around with a floor fan. It never cycles "off & on", rather, if I listen closely I can hear the cooling unit increasing or decreasing speed. The neighbors are very happy as it is almost inaudible. Needless to say I am happy with my purchase. It does kill me when I think about how much money I wasted over almost 10 years with the old unit. Expensive lesson learned.

Edited April 27, 2015 by dddave

[KittenKong]

I did learn enough that I knew if I could buy a unit with an "Inverter" for an affordable price, that was the way to go.

Most appliance department AC salespeople are not very helpful and finding ones with decent English skills not easy. Most would go to their charts and push 30,000 BTU units with inverter types pushing B45,000+++.

With help from this forum, I decided I did not need to go that high. Coincidentally, POWER MALL at Siam Paragon was having it's annual clearance sale and I was able to find a well reviewed SAMSUNG unit, 21,000 BTU with inverter for B22,000 installed. I had done a lot of shopping and that was an amazingly low price for an inverter unit and Samsung is a reasonably reliable mainline manufacturer. It was fully installed and operating within 7 days of purchase.

I have now had it almost 5 months and I just got my power bill for March 16-April 16: B2600 for a very hot 4 weeks, way less than I used to pay, even in cool season. It is on all night and probably half the day, sometimes all day. I run it at 25 degrees and move the air around with a floor fan. It never cycles "off & on", rather, if I listen closely I can hear the cooling unit increasing or decreasing speed. The neighbors are very happy as it is almost inaudible. Needless to say I am happy with my purchase. It does kill me when I think about how much money I wasted over almost 10 years with the old unit. Expensive lesson learned.

Your percentage savings are similar to mine for a similar space and usage, though I spend about 1000B less than you as I set the temperature a couple of degrees higher. The relative silence is a definite advantage.

And your purchase price was very good indeed. I paid quite a lot more for my 24K inverter, though it was still quite reasonable.

[dddave]

Hi KK

I find that with the thermostat set for higher temp...27 degrees and up, I can feel significantly more humidity in the room. That temp. is not bad if I am sitting around with a fan moving air around me but if I start doing any strenuous activity, I get very sweaty, very quickly. 25 seems to dry the air more efficiently. I notice a significantly larger output of water from the drain when at 25. Maybe I'll try to do an experiment and run it at 25 for 30 min and measure the water output, then change to 27 and measure the 30 minute output..might be interesting. I'll report back.

I do often run it at 26 at night.

Edited April 27, 2015 by dddave