Aircon Question - Very Brief

[bangkokburning]

We have a standard AC unit in our flat. Like every apt I had rented in past 15 years, its broken. So...

The ac unit is stuck on maximum cold and fan to medium. On this unit the dial literally does not work and switch to fan low renders it inoperative.

Purely from economics and energy savings, is it better to flip the ac off and on every 20 or 30 minutes when we are freezing or let it run and put on some clothes?

The outside condenser is some oldish thing and inside we are sporting the quality "Unimaster" brand.

Thx!

Edited April 20, 2013 by bangkokburning

[isawasnake]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

[wayned]

If you rented the unit with aircon, why don't you contact the landlord and get it fixed? No brainer!

Edited April 21, 2013 by wayned

[how241]

If you rented the unit with aircon, why don't you contact the landlord and get it fixed? No brainer!

+1...Sounds like a good place to start.

[ExpatOilWorker]

I sugget you just open the windows if it gets too cold.

The Oil&Gas industry appriciate your business.....thanks.

[lucjoker]

if something ,even small, is not working in my rented -out house,they will telephone me the same minute,if i dont repair it quickly ,they will stop paying the rent and go rent somewhere else.

Offcourse if your rent is lower than 10 000 bht,they will not be bothered if you leave,annother thai will come in your place and he will never complain.

[maswov]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

[isawasnake]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

His thermostat is fixed on maximum; that is making the compressor work harder.

People with your logic are the ones that go grocery shopping, movies etc and think it is more energy efficient to leave the air on the entire time, correct? (confused).

[jackflash]

Yes, the best bet is to have the thermostat fixed.

But if that is completely out of the question, you could arrange a external thermostat to switch the A/C on and off based on whatever temperature you set it at.

After all, that is all that the internal thermostat is (or should be) doing.

I've been in this situation myself. Had a A/C which ran continuously but it couldn't be repaired as it was a historic relic (long story).

I scrounged a thermostat from an old fridge and connected that up.

It worked just fine (although the fan stopped and started of course).

Your electrician could make you up a little box with a thermostat and the appropriate plug and sockets.

Edited April 21, 2013 by jackflash

[jackflash]

> His thermostat is fixed on maximum; that is making the compressor work harder.

No, the compressor is either on or off. It can't work harder, only longer.

His thermostat is probably shorted, hence always ON.

Just to clarify, most conventional A/C units are the "Bang/Bang" type. The compressor is either ON or OFF.

It is a simple and cheap method, but tends to overshoot causing temperature fluctuations.

However some modern high-end Japanese units have a variable speed compressor (Inverter style).

They run continuously but their rotation speed is proportional to the load.

The hotter it is, the harder they work. Much quieter and much less temperature fluctuations.

Edited April 21, 2013 by jackflash

[Naam]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

there's no "aircon" in the market that "blows around -5ºC". these units are found in subzero storage rooms.

[Naam]

Yes, the best bet is to have the thermostat fixed.

But if that is completely out of the question, you could arrange a external thermostat to switch the A/C on and off based on whatever temperature you set it at.

After all, that is all that the internal thermostat is (or should be) doing.

I've been in this situation myself. Had a A/C which ran continuously but it couldn't be repaired as it was a historic relic (long story).

I scrounged a thermostat from an old fridge and connected that up.

It worked just fine (although the fan stopped and started of course).

If you do this you need to check that your thermostat can handle the start current of the A/C.

thermostats of aircon units do not handle starting currents. they handle relays and starting capacitors which handle starting currents.

[Naam]

to the OP. the advice "change Thermostat" should solve the problem. that is... if you are able to find a thermostat that can be fitted in the rather old unit. but a clever electrician (some do exist in Thailand!) will be able to do the job.

[jackflash]

> thermostats of aircon units do not handle starting currents. they handle
relays and starting capacitors which handle starting currents.

(some confusion here as I apparently edited my post after your post)

Old style fridge thermostats handled large currents (had big contacts).

Modern electronic thermostats use solid state devices to do the switching,

Needless to say, you do need to check their ratings. Or use a relay.

Modern A/C units of course don't have "thermostats" as such. It is all just part of the embedded software.

Hence the suggestion to fit something external if it can't be repaired.

Edited April 21, 2013 by jackflash

[maswov]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

His thermostat is fixed on maximum; that is making the compressor work harder.

People with your logic are the ones that go grocery shopping, movies etc and think it is more energy efficient to leave the air on the entire time, correct? (confused).

Sorry, didn't mean to offend you, there is a difference between longer and harder. The compressor will will pressurize the refrigerant to the same pressure no matter what temp the thermostat is set to therefore utilizing the same amount of energy (in other words the same amount of work) over a given time period. Maybe a quick trip to 7 will be better to leave it on but not grocery shopping and movies.

[maswov]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

there's no "aircon" in the market that "blows around -5ºC". these units are found in subzero storage rooms.

Check the properties for refrigerants particularly the evaporator temperature. I am mistaken though, R134a is being used more often now which is -10C.

[davejones]

Get it fixed. I have no idea why you want to continue using it if it's broken.

[Naam]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

there's no "aircon" in the market that "blows around -5ºC". these units are found in subzero storage rooms.

Check the properties for refrigerants particularly the evaporator temperature. I am mistaken though, R134a is being used more often now which is -10C.

any air flow below +5ºC would cause evaporator icing in less than 30 minutes of operation. exceptions: if aircon is operated in areas with an ambient relative humidity of less than 20%, a situation that does not exist in a home in Thailand. but even then icing would occur after hours of continous compressor operation.

note: refrigerant evaporation temperature is neither equal to evaporator fin temperature nor air flow temperature.

[Naam]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

His thermostat is fixed on maximum; that is making the compressor work harder.

People with your logic are the ones that go grocery shopping, movies etc and think it is more energy efficient to leave the air on the entire time, correct? (confused).

Sorry, didn't mean to offend you, there is a difference between longer and harder. The compressor will will pressurize the refrigerant to the same pressure no matter what temp the thermostat is set to therefore utilizing the same amount of energy (in other words the same amount of work) over a given time period. Maybe a quick trip to 7 will be better to leave it on but not grocery shopping and movies.

"there is a difference between longer and harder"

the optimum is a combination of both!

[maswov]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

there's no "aircon" in the market that "blows around -5ºC". these units are found in subzero storage rooms.

Check the properties for refrigerants particularly the evaporator temperature. I am mistaken though, R134a is being used more often now which is -10C.

any air flow below +5ºC would cause evaporator icing in less than 30 minutes of operation. exceptions: if aircon is operated in areas with an ambient relative humidity of less than 20%, a situation that does not exist in a home in Thailand. but even then icing would occur after hours of continous compressor operation.

note: refrigerant evaporation temperature is neither equal to evaporator fin temperature nor air flow temperature.

Yes, that is why they ice periodically.

OK, so the air temp does not equal evap temp that is common sense. There is not enough time for the full amount of thermal energy to transfer from the air to the refrigerant. I didn't think it was necessary to use the convection thermal energy transfer equation to get the temp, would need the ambient temp and flow rate to calculate anyway.

[Naam]

let's not confuse the OP. he has to change the thermostat to solve his problem.

[Razzler1973]

He has to get the landlord to do it

[Sydebolle]

Get the fan coil cleaned and you should be OK. The unit freezes as the air cannot circulate through the cooling blades fast enough and hence, due to the condensation, freezes over. Basics though........

[Pacificperson]

Turning the unit off and on manually will save you energy (and money). It sounds like it time to bite the bullet and offer to split the cost of a new unit with the landlord. If you are going to be in the apartment for a year or more, you will most likely come out ahead.

[Naam]

Get the fan coil cleaned and you should be OK. The unit freezes as the air cannot circulate through the cooling blades fast enough and hence, due to the condensation, freezes over. Basics though........

a [not so] fitting diagnosis. the OP mentioned nothing about freezing/ice forming but "stuck on max cold" and "we are freezing". if ice had formed which blocks the airflow they "wouldn't be freezing".

[Pacificperson]

OP - Is this one of the really old fashioned floor mounted, split units with dials for both the fan speed and temperature settings?

[54321]

Turning the unit off and on manually will save you energy (and money). It sounds like it time to bite the bullet and offer to split the cost of a new unit with the landlord. If you are going to be in the apartment for a year or more, you will most likely come out ahead.

please rent my condo, if you are willing to split the cost of any failing equipment

[Pacificperson]

I am also a landlord. I have sometimes chipped in when a tenant wants something that I don't think is necessary, but I can see it increasing the value of the unit. More often, my response is OK I'll buy it, but your rent is going up. The tenant pays one way or the other.

His AC unit is still functioning, if not optimally. His landlord may not see it as a problem to be dealt with. However, if the savings on his electric bill are more than 1/2 the cost of new AC, he still comes out ahead and maybe he can get the landlord to spend some money. Over the course of a year, it might be worth it simply not to have to turn the aircon off and on every 20 minutes.

[bangkokburning]

Wow. Well a certainly have some answers!

Honestly, never thought of asking the office. They seem like they would be indifferent as its "working" (gets cold). They are good about maintenance though.

We will be changing to another flat when one frees up, but I was just curious. We don't use it all that much, an hour a day and few hrs on weekend in warmer months.

I dont want to theaten to move, I like the place!

Thanks for the education - really.

PS unit is standard bog box outside the unit with a newer blower thingy inside. Seems to me the dial is jacked up on the temp but also when fan is moved from M to L it shuts the whole unit down. Comes back on and only fan works for five mins. Not my problem, just hate to waste money and bad for environment.

Edited April 22, 2013 by bangkokburning

[isawasnake]

It isn't any different from a light bulb or anything else. It will definitely be better to turn it off when you get cold. You say it is stuck on maximum cold, that does make the compressor work a lot harder, but I think you can counteract that for the most part by turning it on/off as you say.

The compressor won't work harder, only longer, and possibly constant. The AC will blow around -5C, the thermostat on your system will tell the compressor when to turn on and off depending on what temp you set it. Turning it on and off manually will probably result in higher energy costs because you will most likely exceed your desired temp often allowing the compressor to run longer, further you will probably turn it on later than normal requiring a longer running time to reduce the room temp. Best bet is to have the thermostat fixed.

His thermostat is fixed on maximum; that is making the compressor work harder.

People with your logic are the ones that go grocery shopping, movies etc and think it is more energy efficient to leave the air on the entire time, correct? (confused).

Sorry, didn't mean to offend you, there is a difference between longer and harder. The compressor will will pressurize the refrigerant to the same pressure no matter what temp the thermostat is set to therefore utilizing the same amount of energy (in other words the same amount of work) over a given time period. Maybe a quick trip to 7 will be better to leave it on but not grocery shopping and movies.

So, considering his circumstances, your advice is to just leave it on after he gets too cold? And that will save him energy/money is your contention? And according to you, there is no such thing as a compressor duty cycle (ie, high and low duty cycles)Either way, my vote is turning the ac off when you get too cold will save energy. So, op must decide between these very confusing options I guess. I mean, who would have though that I can get too cold and leave the ac on full blast, all while saving energy! These are amazing new discoveries in thermodynamics we are making here.

Edited April 22, 2013 by isawasnake