No matter how low I set thermostat aircon won't get below 29

[swoods58]

When he say something like the coil in a car was replaced I think he means the motor start capacitor. Thus wouldn't affect anything else.

[Pib]

When he say something like the coil in a car was replaced I think he means the motor start capacitor. Thus wouldn't affect anything else.

Yea...that could be what he means as it would be shaped in a similar way. Hopefully he will clarify. The outside unit compressor and/or fan start capacitor would be located in the outside unit. I've changed a couple of mine over the years...in fact, changed one about a month ago. Pretty easy and cheap.

[innerspace]

The site you mentioned in sq feet, suggests American. What humidity and average temperature in the town that the guide comes from?

12000 but will cool 500sqm in alaska or 15sqm in nevada desert.

Cooling guides need to be region specific.

[rodknock]

my bedroom had a 9000btu and living room 13000btu. did not cool well especially in the hot season.

my awesome landlady replaced a/c's for me. put 12000btu in bedroom and 18000btu in living room.

now i have good a/c.

[giddyup]

When he say something like the coil in a car was replaced I think he means the motor start capacitor. Thus wouldn't affect anything else.

Yea...that could be what he means as it would be shaped in a similar way. Hopefully he will clarify. The outside unit compressor and/or fan start capacitor would be located in the outside unit. I've changed a couple of mine over the years...in fact, changed one about a month ago. Pretty easy and cheap.

Yes, it was the capacitor, charged me 1200 baht for that.

[giddyup]

It aint big enough giddyup sorry..............

Right, with days reaching 40c, there's not much chance of just 12,000 BTU in a 30sqm room coping well.

According to Daikin, 18,000 BTU is where it starts for this size room: http://www.daikin.co.th/service-btu-calculation/

According to my own experience in a similar sized room (5.5 x 6.0M), with a few heat sources, a dormer section (5M high), but no direct sunlight, 24,000 BTU isn't even enough on a 40c day. I recently upgraded that one to 33,000 BTU, which does the job - but even so, can still only get the room to 23c when it's 40c outside.

The little research I did showed that a 12,000 BTU aircon would service a 450-550 sq. foot room. My room is approx. 5 x 4 metres = 20 sq. metres = 215 square feet, or less than half of what the aircon is capable of cooling.

Your room must have shrunken in the laundry, because a few posts ago it was still 5 x 6 = 30m²

It's still 5 X 6, my mistake.

[IMHO]

It's still 5 X 6, my mistake.

OK well in that case, at 400 BTU/sqm your issue is simply not enough BTU.

Most Thai AC installers will use a base of around 500-600 BTU/sqm, then add on top of that for rooms with heat sources, sunlight, hot roof's above them, number of people, longer piping between indoor/outdoor etc - in more extreme cases ending as high as 1000 BTU/sqm.

The Daikin calculator is a realistic guide for what's needed to work in Thai conditions.

[IMHO]

OP,

Your 12K BTU is plenty big enough for your room...I have a 8K BTU in a room your size and it cools it down just fine after about 10 minutes but I will admit I have it set to only pull down to 25C.

Also wish you could better describe "they replaced something that looks like a coil in a car." When I read that I thought "did they replaced the entire evaporator/inside cooling fins & coils?" Probably not because that would be big money...would requiring the ordering for the fins/coils, major job....they would just instead say replace the whole A/C. But maybe you were talking a "thermostat?" But usually a thermostat is just a straight looking short tube.

Also, you said they cleaned the unit. Does that include the "outside unit called the condensor/compressor? If the outside unit fins/coils are too dirty it can degrade cooling performance a lot and cause much higher electric bills.

Also how and where are you measuring the room temperature? Some kind of thermometer hanging on the wall, in a digital clock, etc? You can have "wide variations" of temperature within a room. Remember your A/C is measuring the temperature at one location only and that location is a temperature probe most likely mounted on the inside cooling unit fins/coils...just behind the filter you change. It's basically measuring the air that is returning to the inside unit to be pushed through the cooling fins/coils again, cooled down again, and pushed back out into the room.

Pulling down to 23C in this HOT weather could be challenge/take a while. Also is the outside unit/condenser/compressor always running in attempting to pull down to 23C...I expect it would be in this daytime hot weather. If it's not running close to 100% then maybe you just have a temperature measuring problem.

His room is now confirmed at 30sqm, not 20sqm

[shaurene]

AI am into air conditioning in New Zealand.

Your area is 5x6 = 30 sqr mts. You have a 12,000btu which is 3.5kw.

For hot countries like Thailand you need to calculate 1 kW per 6 sqr mts. So your unit is well under power, your 12,000btu would only be sufficient for 20sqr mt. You need at least 5kw 18,000btu

It gets very dusty in Thailand, we have a house in Khon Kaen we need to get ours cleaned each j5-6 months.

[IMHO]

The standard formula to calculate btu here is; area sqm × 800= necessary btu needed. This is for a normal room. In your case

30×800=24000 btu. I would say you need a larger ac.

Right, 800/sqm would be for a room that's used during the day, has some sunlight (but not a whole glass wall), has a roof above it (not another floor above), and has a few heat sources like a TV, fridge, Hi-Fi, etc, and more than 1 or 2 people to cool down.

i.e. a typical living room in a single storey house.

If you lived in a North facing condo with a balcony and a floor above and below, and are living alone, 500 BTU/sqm would probably be totally adequate though - 400 BTU/sqm would probably even work on days where it doesn't get past mid 30's.

[Jing Joe]

A basic check of a manual rotating thermostat knob was >> before you turn on A/C power (and the thermostat is therefore at room temp), twiddle the dial and listen for the on/off clicks which should co-incide with room temp somewhere "sensible"? on the knob, (bear in mind what HooHaa suggested about knob numbering relevancy). Your 7 yo A/C may not have knob? so maybe first adjust the digital reading to the inside/outside temp and the slowly adjust it downwards till you hear the compressor start up. If something doesn't add up, maybe the thermostat is "off". But need to be wary of the comp starting if it is a reverse cycle?Models vary.

Another thought; was the "coil" part of the capillary tube, coiled-up, that used to be part of thermostats?

Did the sensing bulb at the end of the capillary tube go back properly IF it was replaced? Some were strapped to the output side of the evaporator fins?

There used to be adjusting set-screws on thermostats not just for temp setting but differential. Did someone else fiddle?

Is ice forming in the evaporator fins from the frozen humidity? many A/C wont tolerate too low a temp setting and motel owners typically warn customers.

Low gas? as others have said.

Too small? as others have said.

Thermostat bulb location incorrect as Pib suggested.

Edited April 6, 2016 by Jing Joe

[Crossy]

I've not read everything, but the beast is in the correct mode isn't it? Having it set to "Dry" would have similar symptoms to what our OP is describing.

And yes, it's too small.

[HooHaa]

It aint big enough giddyup sorry..............

Am I supposed to take your word for that, or do you have some information that backs up your statement? According to a Google search, a 12,000 BTU aircon will service between 450-550 square feet. My bedroom is nowhere like that big.

The most common window air conditioning units come in cooling capacities ranging from 5,000 to 12,000 Btu. A 12,000 Btu air conditioner can cool between 450 and 550 square feet of floor space. A 12,000 Btu unit could cool a room 25 feet long by 20 feet wide that has 500 square feet of floor area. Manufacturers give their own ratings as to how much room area they believe their units can cool.

well the problem is obvious, the air conditioner was only designed to cool a room of metric dimensions.

more to the point, i believe your calculations are for a different climate and assuming higher insulation levels than are common here, a common problem with US based calculators.

generally id would say 12000 btu tops out at less than 350 square feet, or for the rest of the world approx 30 square meters.

get an 18000 btu unit and you will be chilling pretty.

[giddyup]

Thanks everyone. The general consensus seem to be that the aircon is too small, but that is something that I'll have to live with, because the aircon will cool the room enough so that it's comfortable (28 degrees), and it cuts out at that temp. so it's not running continuously, so I'm not prepared to buy a new aircon just so I can get it down to 25 or 23, which is probably too cold anyway.

[Beats56]

Was it doing this before it was "serviced" ?

Actually just prior to service it was blowing too cold, and then the next day there was no cold air, that's when I called in the "experts" for a service.

[Beats56]

The part they replies is the capacitor. It kicks the compressor on. Had mine replaced too. I usually set it for 22C. I like it cold and I am from Canada but in Southwest Ontario it gets hot and humid like Thailand in the summer.

[giddyup]

The part they replies is the capacitor. It kicks the compressor on. Had mine replaced too. I usually set it for 22C. I like it cold and I am from Canada but in Southwest Ontario it gets hot and humid like Thailand in the summer.

That temp. would have me under the blankets, I could never leave the bedroom if I had it that cold, the outside temperature (37c) would kill you with the shock.

[Beats56]

I was brought up like that my father hated the humidity. I think we had ac before a tv

In the winter I would sleep with window slightly open with lots of blankets. Love a cold room. Haha

[Pib]

When he say something like the coil in a car was replaced I think he means the motor start capacitor. Thus wouldn't affect anything else.

Yea...that could be what he means as it would be shaped in a similar way. Hopefully he will clarify. The outside unit compressor and/or fan start capacitor would be located in the outside unit. I've changed a couple of mine over the years...in fact, changed one about a month ago. Pretty easy and cheap.

Yes, it was the capacitor, charged me 1200 baht for that.

OK, the start/run capacitor only kick-starts the outside unit compressor/gets it going (kinda like how a starter starts a vehicle and then removed from the circuit) and then is taken out of the circuit within a few seconds of compressor startup. The big fan on your condensor/compressor/outside unit also has a run capacitor (just like in a table/floor fan) that ensures the unit's fan starts easily and keeps turning...this capacitor remains in the electrical circuit all the time, is much smaller than the compressor start capacitor. Sometimes the start and run capacitor are a single combo unit.

The large start capacitor is normally around 35-50 microfarad and about the size of a small Cola can (or car coil) costs approx Bt150. The small fan capacitor is normally around 1.5 to 5 microfarad, about the size of a match box, and costs around Bt50. I've bought some over the years for my A/C systems. Got a spare of each right now of each in standby if/when one of my A/Cs fail again due to such a capacitor. Fan run capacitors last much longer than compressor start capacitors since the compressor start capacitor pulls a great deal of current/amps for a few seconds during compressor start up. You can get them at Amorn Electronic stores and other electronic shops...that's were I get mine at Amorn Electronic stores which are usually found in/close to Tesco Louts stores...they also sell a variety of other capacitors for fans, water pumps, etc. As you found out the A/C tech adds quite a mark-up to cover his labor costs.

Anyway, assuming your compressor is starting and the fan is running that is not your problem. The cooling problem is else where in the A/C system. Be sure both the outside and inside unit are clean.

[Pib]

Thanks everyone. The general consensus seem to be that the aircon is too small, but that is something that I'll have to live with, because the aircon will cool the room enough so that it's comfortable (28 degrees), and it cuts out at that temp. so it's not running continuously, so I'm not prepared to buy a new aircon just so I can get it down to 25 or 23, which is probably too cold anyway.

If you set the temp to it's lowest setting...probably somewhere down around 20C the A/C's outside unit should never or only very briefly stop running simply because its still trying to pull down to that 20C temp in this hot Thailand weather. If you have a small/cheap thermometer you can place about a inch within the inside unit's output louvers (but don't poke it far enough to hit the spinning cage fan inside) your output temperature should be around 50 to 55C during the day...if you get lower than 50C that's even better....if higher than 55C you A/C is struggling to cool/there is a problem/it's undersized/etc.

[giddyup]

Thanks everyone. The general consensus seem to be that the aircon is too small, but that is something that I'll have to live with, because the aircon will cool the room enough so that it's comfortable (28 degrees), and it cuts out at that temp. so it's not running continuously, so I'm not prepared to buy a new aircon just so I can get it down to 25 or 23, which is probably too cold anyway.

If you set the temp to it's lowest setting...probably somewhere down around 20C the A/C's outside unit should never or only very briefly stop running simply because its still trying to pull down to that 20C temp in this hot Thailand weather. If you have a small/cheap thermometer you can place about a inch within the inside unit's output louvers (but don't poke it far enough to hit the spinning cage fan inside) your output temperature should be around 50 to 55C during the day...if you get lower than 50C that's even better....if higher than 55C you A/C is struggling to cool/there is a problem/it's undersized/etc.

The aircon motor is on the north side of the house, so is in the shade permanently, so I doubt if it ever gets as hot as 50-55 degrees.

[Pib]

Thanks everyone. The general consensus seem to be that the aircon is too small, but that is something that I'll have to live with, because the aircon will cool the room enough so that it's comfortable (28 degrees), and it cuts out at that temp. so it's not running continuously, so I'm not prepared to buy a new aircon just so I can get it down to 25 or 23, which is probably too cold anyway.

If you set the temp to it's lowest setting...probably somewhere down around 20C the A/C's outside unit should never or only very briefly stop running simply because its still trying to pull down to that 20C temp in this hot Thailand weather. If you have a small/cheap thermometer you can place about a inch within the inside unit's output louvers (but don't poke it far enough to hit the spinning cage fan inside) your output temperature should be around 50 to 55C during the day...if you get lower than 50C that's even better....if higher than 55C you A/C is struggling to cool/there is a problem/it's undersized/etc.

The aircon motor is on the north side of the house, so is in the shade permanently, so I doubt if it ever gets as hot as 50-55 degrees.

Correction...I meant 50 to 55F output air temp or 10 to 13C. And I'm talking the inside unit to be clear...not the outside unit.

[ignis]

do not use air often, but last year had a problem, called the service guy, he and his wife came next day [as have done for past 12 years] = clean and service and was low on gas... called him again next day, worked fine but after 10 mins was working not good.......... turned out the bearings in the fan in the outside unit was bad, this was replaced and all was fine again..

Just saying when your service person left it could have been like mine was working fine, but after a while the fan went on a go slow = not cooling. [bearing ceasing when hot] try standing under the unit and switch on and see if it is cold when starting and maybe feels not so cold after a short time

It is hot now, and have been using this unit upstairs in the master bedroom for the past week, set on 25 = cold all night + this unit is just over 12 years old. out of interest the bedroom is 7m x 4 m and Air Con is a Panasonic 12,000btu

[StefanBBK]

the numbers showing on a thermostat, especially the old dial thermostat are largely arbitrary.

there is also the possibility that the unit is under powered for the room or season, or both.

Plus the air conditioning does not adequately measure the temperature across the room....

[pattjock]

Most aircon units with a digital remote have two temperature sensors. One sensor in the remote and another sensor in the wall unit.

When you set a temperature on your remote the the a/c will stop when this temperature is reached AT THE SENSOR YOU HAVE SELECTED.

You usually select the sensor you want to use with a switch on the wall unit or sometimes on the remote.

If you set a temp of 23 deg on the remote and have selected the temp sensor in the wall unit you may never reach this temp as the wall unit is usually mounted high (the room will be much hotter near the celing than near the floor) and the wall next to the wall unit may be hot.

Normally you should select to use the temp sensor in the remote and keep the remote at the same height as your bed, that way you will get the temperature you set on the remote at the location you will be during the night.

[chilli42]

the numbers showing on a thermostat, especially the old dial thermostat are largely arbitrary.

there is also the possibility that the unit is under powered for the room or season, or both.

One other thing to consider. We bought a fairly new second home. The air con equipment was very high end. No matter what we did, could not get the room temp below 25. It turns out our problem was that the compressor was too far from the room unit. One other thought, did you top up or change the cooling gas (freon?) in the compressor? Good luck

[petermik]

It aint big enough giddyup sorry..............

It aint big enough giddyup sorry..............

Am I supposed to take your word for that, or do you have some information that backs up your statement? According to a Google search, a 12,000 BTU aircon will service between 450-550 square feet. My bedroom is nowhere like that big.

The most common window air conditioning units come in cooling capacities ranging from 5,000 to 12,000 Btu. A 12,000 Btu air conditioner can cool between 450 and 550 square feet of floor space. A 12,000 Btu unit could cool a room 25 feet long by 20 feet wide that has 500 square feet of floor area. Manufacturers give their own ratings as to how much room area they believe their units can cool.

Thanks everyone. The general consensus seem to be that the aircon is too small, but that is something that I'll have to live with, because the aircon will cool the room enough so that it's comfortable (28 degrees), and it cuts out at that temp. so it's not running continuously, so I'm not prepared to buy a new aircon just so I can get it down to 25 or 23, which is probably too cold anyway.

At last giddyup

[Mudcrab]

A couple of simple questions:

Did the air con work well prior to service/rebuild?

If it did - why doesn't it now?

What has changed?

Answer this and you will find your solution.

[briley]

How long is too long for the pipes from the inside to the outside unit?

Or how short should they be before you have to take them into account in deciding on how many BTU you need?

Edited April 13, 2016 by briley

[Pib]

How long is too long for the pipes from the inside to the outside unit?

Or how short should they be before you have to take them into account in deciding on how many BTU you need?

It will vary from manufacturer to manufacturer as to their recommendation for shortest and longest length freon piping for a typical home split AC, but it's usually around 1.5M minimum to around 20 to 25M maximum. A new unit will usually come precharged based on the assumption the freon pipes will be approx 5M in length with instructions on how much additional freon to add per meter additional length beyond the normal. BTU size needs to be based primarily on the size of the area you are cooling (but other factors come in to play also like number windows, number of people, room use, etc); not how long your freon pipes are between the inside and outside units.