Air Con Mathmatics.........

[grnelson75]

To extend this subject a bit more, I was once told that running the ceiling fan (on low), together with the a/c, was cheaper and more efficient than running the a/c unit alone - something to do with a more even spread of the cold air. Any comments?

Anyway, with the ceiling fan running, I run the a/c at 27 degrees, (starting about an hour before bed), then knock off the a/c about 3.00am when I get up for a pee. That seems to work quite well for us, the coolness seems to persist with just the ceiling fan running.

I think the key is to ensure that the a/c is also drawing out the humidity. I can't be dealing with humidity when it's either hot or cool.

I do the same, run AC and a fan. A fan will spread out the cold air and provide evaporative cooling. End result, the same comfort level can be had at a higher temp setting on the AC. Since the AC is the money pit in this setup, your overall electric bill s/b lower.

[oldgit]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

That cannot be done with a normal wall mounted unit. You will need either a ceiling mounted cassette unit or an in ceiling ducted unit. Both have a fresh air facility for ducted air from outside. The downside is I have never seen these for sale in Thailand although they are common in England.

[oldgit]

To extend this subject a bit more, I was once told that running the ceiling fan (on low), together with the a/c, was cheaper and more efficient than running the a/c unit alone - something to do with a more even spread of the cold air. Any comments?

Anyway, with the ceiling fan running, I run the a/c at 27 degrees, (starting about an hour before bed), then knock off the a/c about 3.00am when I get up for a pee. That seems to work quite well for us, the coolness seems to persist with just the ceiling fan running.

I think the key is to ensure that the a/c is also drawing out the humidity. I can't be dealing with humidity when it's either hot or cool.

I do the same, run AC and a fan. A fan will spread out the cold air and provide evaporative cooling. End result, the same comfort level can be had at a higher temp setting on the AC. Since the AC is the money pit in this setup, your overall electric bill s/b lower.

Because the normal wall mounted unit has a direct expansion coil (freon gas R22 which is still widely used in Thailand but has been superceded in UK),it will automatically dehumidify the air in the room.

[Carib]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

The purpose of the A/C is to extract water from the air inside the to be cooled room, if you will lead continues moist fresh air in from outside the room it will not be able to cool the room down, or you will have the idea of it being cool, but the air stays moist, that is what makes it not feel right.

Edited May 18, 2013 by Carib

[oldgit]

I just installed soem air cons. I was told that one room needed 24,000 BTU. The mooban staff told me to get two 12,000 BTU air cons instead, that they would work better.

When the Mitsubishi guy came to install, after the fact, he asked me why I did it that way, that the architect designed it for one 24,000 BTU unit.

I am finding that the two smaller units are having problems pushing the air far enough, so I now use a fan to help circulate the cool air.

Each size unit has a certain 'throw of air'. The larger the unit,the further the throw. Normally,you will have a three speed facility, on the remote controller for each unit so make sure it's set on high speed. Maybe they suggested you have two split units because you have an odd shape room?

[jpinx]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

That cannot be done with a normal wall mounted unit. You will need either a ceiling mounted cassette unit or an in ceiling ducted unit. Both have a fresh air facility for ducted air from outside. The downside is I have never seen these for sale in Thailand although they are common in England.

Cool I never had a need for A/C in UK - hence my ignorance. I'll explore further - thanks for the pointer

[jpinx]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

The purpose of the A/C is to extract water from the air inside the to be cooled room, if you will lead continues moist fresh air in from outside the room it will not be able to cool the room down.

I was thinking the fresh air option would probably work the cooler harder, but my setting is not so low. Even the BTS units are way too cold for me.

[Carib]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

The purpose of the A/C is to extract water from the air inside the to be cooled room, if you will lead continues moist fresh air in from outside the room it will not be able to cool the room down.

I was thinking the fresh air option would probably work the cooler harder, but my setting is not so low. Even the BTS units are way too cold for me.

Cooler never works harder, it is either on or off, it just take longer to reach a certain temperature. Adding fresh air will make it work longer, moisture extraction (evaporation process) from the air inside the room is what makes it cool down.

[PalMan]

It isn't at all difficult to acclimatize your body to no longer need A/C at all.

This from a very overweight farang who usually feels hotter when others are comfortable, grew up in a very cold climate, sweat a lot.

[Torrens54]

The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract insects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

[Anon999]

My a/c units have 3 modes auto, cool and dry. During this time of year when it's humid, I always set them to Dry and 27C. That brings the humidity down a long way to into the 30+% range. When it's up in between 60% - 70%, whatever the temperature it's uncomfortable.

[Anon999]

The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract insects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

My house has the padded foil under the tiles and 6 inches of foil wrapped fibreglass insulation in the loft same as in the UK. Even with aerated concrete block walls and rubbish double glazing, 6mm air gap, the house can still get quite hot, however, the a/c cools it down quickly. It's far better than the rent house I lived in where everything was the same temp as outside, including the bed, clothes, furniture, the lot. it just started to cool off by sunrise. The a/c couldn't cope and seeing the bed temp was often 100+F (38C) most uncomfortable.

The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract insects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

Edited May 18, 2013 by Anon999

[BradinAsia]

Don't know where the OP lives, but in CNX the temp get down to about 24 degrees at night.

Best way to get a good comfortable night's sleep without wasting electric -- turn off the air-con,

open the bedroom window, put a floor fan inside the window to draw cool outside air in all night.

Saves a lot of electric.

[Naam]

another aircon thread with expert postings. reading them i have a hard time to make up my mind..... whether to laugh out loud or cry bitterly. no offence meant!

[RBOP]

I suggest an Inverter Air-Conditioner for the bedroom. They cost a little more but they are quieter and temperature fluctuations less. There's a little savings on power too. For sleeping I set mine to 21C and my thermometer will read 21.5 all night. Of coarse one can set it to other temperatures. In my living room for watching tv etc I put the aircon to 26 to 28C. I have 5 aircons but usually only 2 ever run at the same time. My bill is 5 to 5.5K Baht per month.

[bonobo]

I just installed soem air cons. I was told that one room needed 24,000 BTU. The mooban staff told me to get two 12,000 BTU air cons instead, that they would work better.

When the Mitsubishi guy came to install, after the fact, he asked me why I did it that way, that the architect designed it for one 24,000 BTU unit.

I am finding that the two smaller units are having problems pushing the air far enough, so I now use a fan to help circulate the cool air.

Each size unit has a certain 'throw of air'. The larger the unit,the further the throw. Normally,you will have a three speed facility, on the remote controller for each unit so make sure it's set on high speed. Maybe they suggested you have two split units because you have an odd shape room?

The room is pretty standard. I think the mooban had it wrong. The installation guy showed me where the electric was there for the larger unit, and he said that the bigger size would be much better than the two smaller size. It would have saved me some baht as well.

With the fan, that makes is OK, though. It helps the smaller units with their throw (is that the official terminology? "Throw?" Makes sense if it is. Learn something new every day.)

[RBOP]

The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract insects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

My house has the padded foil under the tiles and 6 inches of foil wrapped fibreglass insulation in the loft same as in the UK. Even with aerated concrete block walls and rubbish double glazing, 6mm air gap, the house can still get quite hot, however, the a/c cools it down quickly. It's far better than the rent house I lived in where everything was the same temp as outside, including the bed, clothes, furniture, the lot. it just started to cool off by sunrise. The a/c couldn't cope and seeing the bed temp was often 100+F (38C) most uncomfortable.

>The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract insects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

A few months ago I installed a 27,600btu Celling Cassette unit in my living room. Mitsubishi Electric PL-3BAKLCME-T for 63,500 Baht. I'm very happy with the unit but the installation guy made a mess of my ceiling. He cut the whole too big and now I have a 1 inch gap on one side.

[Wally4]

a/c ON before retiring to bed to cool bedroom down. Ceiling fan and standing fan (aimed at bed) on when going to bed, a/c off. Should keep reasonable cool rest of night.

All a/c's should be regularly run for 15-20 mins or so even in the cooler seasons in order to circulate the liquid gas to precvent the seals from drying which can reduce their effectiveness.

Remove and clean filters regularly - an easy DIY job.

[oldgit]

My house has the padded foil under the tiles and 6 inches of foil wrapped fibreglass insulation in the loft same as in the UK. Even with aerated concrete block walls and rubbish double glazing, 6mm air gap, the house can still get quite hot, however, the a/c cools it down quickly. It's far better than the rent house I lived in where everything was the same temp as outside, including the bed, clothes, furniture, the lot. it just started to cool off by sunrise. The a/c couldn't cope and seeing the bed temp was often 100+F (38C) most uncomfortable.

>The reason that the temps stay so hot all night is we live in these cement 'heat sinks' that absorb and store the heat in the walls and especially those terrible cement roof tiles, then radiate it down on us all night.

The coolest houses here are the old style grass roof and bamboo walls and floors, but they are so messy and attract in

sects.

Don't seem to find many places with ROOF INSULATION here (in CNX) if anyone knows of a good product and someone who knows how to install it, please let me know.

Murray. CNX.

A few months ago I installed a 27,600btu Celling Cassette unit in my living room. Mitsubishi Electric PL-3BAKLCME-T for 63,500 Baht. I'm very happy with the unit but the installation guy made a mess of my ceiling. He cut the whole too big and now I have a 1 inch gap on one side.

It sounds like he cut the hole to suit the fascia grille instead of the unit housing. Where did you buy the unit? Good choice in choosing Mitsubishi,by the way.

[taotoo]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

The purpose of the A/C is to extract water from the air inside the to be cooled room, if you will lead continues moist fresh air in from outside the room it will not be able to cool the room down.

I was thinking the fresh air option would probably work the cooler harder, but my setting is not so low. Even the BTS units are way too cold for me.

Cooler never works harder, it is either on or off, it just take longer to reach a certain temperature. Adding fresh air will make it work longer, moisture extraction (evaporation process) from the air inside the room is what makes it cool down.

Presumably this is the same thing as turning off recycle in your car. Temperature goes up and you can smell the humidity.

[Mudcrab]

The downside of A/C is the lack of fresh air. I'm considering ducting air from outside to the "suck" vents on the ac unit. Anyone tried that?

The purpose of the A/C is to extract water from the air inside the to be cooled room, if you will lead continues moist fresh air in from outside the room it will not be able to cool the room down, or you will have the idea of it being cool, but the air stays moist, that is what makes it not feel right.

yes you are absolutely correct as the temperature drops so does the dew point and hence the humidity of the room. As we both know that is why air cons have a drain pipe....to take the condensed water away ( for the uninformed an air conditioning unit has two main functional parts...the evaporator and the condenser...gee there's a hint). And the closed air circulation as opposed to bringing in fresh air from outside is far more efficient for the reasons you described.

I am amazed at the number of people who do not understand how to use an air conditioner...."I set it on 18".....good luck, chances are it will never get there. My ex missus used to insist on having the a/c set to "arctic" and then sleep all night under sheets, doonas, (quilts whatever you call them where you are from) to keep warm.

Set the temperature to whatever you are comfortable with......take time to experiment with this. If you wake up cold after this has been sorted out.....fair chance that the outside temperature is lower then the inside temperature...and the a/c isn't working anyway. Buy a reverse cycle unit that can heat as well as cool. (by the way anyone who says it doesn't get cold in the tropics hasn't been there).

And clean the filters regularly ...weekly even if necessary...surprising how much crap can build up in a short time.

Best of all install ceiling fans, vey effective and a good aid to the air conditioner. Its all about how you "feel" not the temperature on a display.

Edited May 19, 2013 by Mudcrab

[jpinx]

The unit will work a bit harder because outside air is hotter than indoor air being recirculated. Humidity will possible not be that much different considering the sweaty bodies and heavy breathing in the room. The benefits of breathing fresh air might outweigh the extra energy use -- might even feel better enough to set is slightly higher. I'm going to try a lash-up with conduits and see how it goes.

[Naam]

As we both know that is why air cons have a drain pipe....to take the
condensed water away ( for the uninformed an air conditioning unit has
two main functional parts...the evaporator and the condenser...gee
there's a hint).

that's not a hint Mudcrab. an aircon's condenser unit condenses gasified

refrigerant (compressing the refrigerant to liquify it) which has nothing to

do with the condense water accumulating on the evaporator fins.

[Vinny1967]

I have my AC set at 25 and automatic.Comes on about every 30 minutes and runs for about 10 minutes.Have the fan running at the bottom of the bed and usually have a good nights sleep.

[SinglePot]

another aircon thread with expert postings. reading them i have a hard time to make up my mind..... whether to laugh out loud or cry bitterly. no offence meant!

afternoon tea and a piece of cake?

[Will2011]

Most of the people set aircon too cold without even knowing why ! They do not try to put it hotter.

When it is 33 outside at night 28 in the room with aircon is far enough.

Another good solution seems to cold the room as much as possible before sleep them stop aircon and use fan.

Both ways comfortable for me but I have been one of these stupid who put 25 all night without even knowing why :-)

Stupid and judgmental as well, I'd say. If people like to set their air con at 18c, it's their business. If they like to set it at 35c, it's their business. I'm not sleeping with them, anyway!

Don't you think I know why I set the temperature at 25?

[SinglePot]

Most of the people set aircon too cold without even knowing why ! They do not try to put it hotter.

When it is 33 outside at night 28 in the room with aircon is far enough.

Another good solution seems to cold the room as much as possible before sleep them stop aircon and use fan.

Both ways comfortable for me but I have been one of these stupid who put 25 all night without even knowing why :-)

Stupid and judgmental as well, I'd say. If people like to set their air con at 18c, it's their business. If they like to set it at 35c, it's their business. I'm not sleeping with them, anyway!

Don't you think I know why I set the temperature at 25?

up to you

[Cheapcharly]

people like to pay more... 18 degree you pay lot more than 26...duh! do you think it was the same price?

my god some have to understand that there is no free exchange of energy. someone has to pay... this is the law of lavoisier, make a Google search..

this is why in usa they burn 50%of the world energy... they never heared about exchange of energy, mass,....

my question, what about these mobile a/c?

[nicoretteMan]

Here's an idea for those DIY types - who just need a little extra cooling... I haven't tried it but it looks promising.

(though I'd keep the water/ice container covered to reduce humidity)

[Will2011]

people like to pay more... 18 degree you pay lot more than 26...duh! do you think it was the same price?

my god some have to understand that there is no free exchange of energy. someone has to pay... this is the law of lavoisier, make a Google search..

this is why in usa they burn 50%of the world energy... they never heared about exchange of energy, mass,....

my question, what about these mobile a/c?

You might need to read earlier posts to understand. You are slightly out of topic.