Air Conditioning Question

[disgruntled]

Air Conditioning...

Okay this is probably a stupid question but is it better to leave the air conditioner on if you are out of the room for an hour rather than shut it off? Someone said to me one that turning it on and off all the time actually wastes more energy because starting it up consumes more than keeping it going. What's you opinion of this? Do your coworkers turn it on and off all day?

Computers...

What about computers as well are there any advantages to leaving them on?

[sigmondfreed]

It would depend on how long you were going out for and how cold you try to keep the room, I would guess.

[Sojourner]

Air Conditioning...

Okay this is probably a stupid question but is it better to leave the air conditioner on if you are out of the room for an hour rather than shut it off? Someone said to me one that turning it on and off all the time actually wastes more energy because starting it up consumes more than keeping it going. What's you opinion of this? Do your coworkers turn it on and off all day?

Computers...

What about computers as well are there any advantages to leaving them on?

The in-rush of current when you start up an air conditioner is momentary and wouldn't really effect your electric bill. Keeping the room cool will allow the airconditioner to cycle normally just to maintain the temperature you desire. The airconditioner will run continiously when you first start it when the room is hot. As mentioned, it really depends how long you will be gone. Regarding your computer, turning a PC on and off will probably cause you to replace components sooner because the printed circuits will cool and then get hot again then cool, etc. This prompts the lead conductors to expand and contract which will eventually cause a break. The best way to save money is to turn off your monitor and leave your computer on. The CRT does suck up a lot of power.

[autonomous_unit]

If your place is anything like mine, i.e. not insulated very well, then I think you're almost surely better off to turn off the air-conditioning when you leave. The only reason to leave it on is for comfort, not for power or equipment savings.

If you turn it off, how quickly does the room warm back up? That gives you an idea of how much heat is pouring into the room, which the air-conditioning is constantly trying to remove again. However, when the room reaches ambient temperature, no more heat pours in! So, it's a bit like running a sump pump continuously against a stream of water, versus letting the basement flood out, and only trying to pump it dry once when you need it... if the amount of water (heat) being pumped out adds up to several room-fulls in an hour, then you're better off just pumping one room-full when you need it.

Also, the rule about computer power saving may not be so accurate these days when people more often have high-powered 3D graphics cards which may burn 100-200 watts as compared to the LCD's less than 50 watts! Unlike laptops, it doesn't seem like desktop graphics cards do much dynamic power saving, i.e. they run hot whether a game is playing or the screen is just showing a static document. Again, just feeling how much heat is pouring out of the vents may give you a good hint as to how much power the devices are consuming.

[longball53098]

I guess I can put my 2 baht worth of comments in here,,,,,,,,,,,,,,,

AC,,,,,,,,,,,,,,if the unit is sized correctly and installed in a place that has proper insulation and such,,,,,,,,,,,,,,,,,it would be much more energy efficient to keep the unit running 24/7,,,,,,,,,,,the biggest electric use is when the compessor is running,,,,,,,,,,,,,,,,the idea of an AC unit is to bring the room/house/facility down to the set temp and then cycle the compressor on and off to maintain the set temp,,,,,,,,,,,,,,,,,for a cool room here in LOS that most likely is about 26 or 27 C for most of us Farangs. But more importantly the AC also removes the humidity from the room and this is what makes you feel comfortable,,,,,,,,,,,,,,,if you switch off the unit to go shopping and then come back an hour later and switch on again,,,,,,,,,,,,the unit must do all the work over again to cool and de-humidify the room,,,,,,,,,,,,,,,,,,,,I have not seen too many rooms here that have proper insulating qualities,,,,,,,,,,,,,,,,,,,,,if they did you could switch off for a period of time as the room will maintain the comfort level for a period of time maybe several hours if insulated well depending on the outside air conditions and the quality of insulation. My experience is in my bedroom where I turn on in the bedtime and set to 27 and the room will cool down and the compressor will cycle all night with a low fan setting,,,,,,,,,,the 13000 BTU unit adds about 50 baht a night to my bill,,,,,,,,,,,the unit typically is on 8 hours. My living room unit which is 35,000 BTU will add about 100 to 125 baht for 6 or 7 hours and keep the room at 27 no problem. But due to poor insulation of the house I am sure I could do better,,,,,,,,,,rental house. If i switch off the living room AC within 30 minutes I have lost all the gain of running the air for 2 or 3 hours,,,,,,,,,,,,I use the living room AC only when really hot and sticky,,,,,,,,,,,,

Most people switch the unit off more for a safety factor than for electric savings,,,,,,,,,,,,,,,,,,,you can't trust the electric wiring here or the units themselves. The installers cut too many corners on wiring practices,,,,,,,,,

As for computer shut downs,,,,,,,,,,,,, you did not say notebook or desktop,,,,,,,,,,,,,,,my feeling is if a notebook then leaving it on is not an issue,,,,,,,,,,,,,,power consumed is very small and heat build up is not a big deal if ,,,,,,,,the big if,,,,,,,,,,,,,,your fan is working and the unit is in an environment not above it's operating range both heat and humidity,,,,,,,,,,,,,if it remains in an uncooled room sitting on a bed (example) where the fan vents are blocked,,,,,,,,,,you run the risk of overheating,,,,,,,,,,,,,,a desktop again won't perform well in an uncooled area but most of them have fans to help keep the box cool,,,,,,,,,,,,,,the CRT does draw the most power and I don't agree about the circuits except maybe for the processor itself,,,,,,,,,,,,,,,,,again a good fan willkeep it at proper temp,,,,,,,,,,the most wear and tear switching on and off is to the hard drive itself,,,,,,,,,,,,,,,,,,,,,if you switch on/off 10 times a day your really risking a hard drive crash prematurely,,,,,,,,,,,

These are just some thoughts from a seasoned AC user and computer user,,,,,,,,,,,,,,,,,,,schooled from the "School of hard knocks"

Edited October 31, 2007 by longball53098

[stateman]

Air Conditioning...

Okay this is probably a stupid question but is it better to leave the air conditioner on if you are out of the room for an hour rather than shut it off? Someone said to me one that turning it on and off all the time actually wastes more energy because starting it up consumes more than keeping it going. What's you opinion of this? Do your coworkers turn it on and off all day?

Computers...

What about computers as well are there any advantages to leaving them on?

1. Your AC actually is turning itself off all the time, as soon as the temp is cold enough per the thermostat setting. So if you manually turn it off when leaving your residence, it won't create any stressful situation for the system.

I'd say logic suggests that it makes sense to turn it off when not using it. OK, when you returns, it may take longer to get the warmer room air to cool down to what you want. That should be expected. But you already saved the elec. usage for the few house you had turned it off.

2. Computer. Many Years ago when hard drive technology wasn't so advanced, it was true that each time you turn the system off, thus turning off the hard drive, the drive's head would 'crash' down. Keep doing it and your hard drive may have a shortened life. This is no longer true for the last several years. It is now ok to turn off your system when not in use.

I turn my pc off several times a day for years and don't have any problem.

My pc which I built uses 500W power supply. If you turn it off, it help save a little bit of coal from needing to be burned - think global warming! :-)

[sleepyjohn]

I guess I can put my 2 baht worth of comments in here,,,,,,,,,,,,,,,

AC,,,,,,,,,,,,,,if the unit is sized correctly and installed in a place that has proper insulation and such,,,,,,,,,,,,,,,,,it would be much more energy efficient to keep the unit running 24/7,,,,,,,,,,,the biggest electric use is when the compessor is running,,,,,,,,,,,,,,,,the idea of an AC unit is to bring the room/house/facility down to the set temp and then cycle the compressor on and off to maintain the set temp,,,,,,,,,,,,,,,,,for a cool room here in LOS that most likely is about 26 or 27 C for most of us Farangs. But more importantly the AC also removes the humidity from the room and this is what makes you feel comfortable,,,,,,,,,,,,,,,if you switch off the unit to go shopping and then come back an hour later and switch on again,,,,,,,,,,,,the unit must do all the work over again to cool and de-humidify the room,,,,,,,,,,,,,,,,,,,,I have not seen too many rooms here that have proper insulating qualities,,,,,,,,,,,,,,,,,,,,,if they did you could switch off for a period of time as the room will maintain the comfort level for a period of time maybe several hours if insulated well depending on the outside air conditions and the quality of insulation. My experience is in my bedroom where I turn on in the bedtime and set to 27 and the room will cool down and the compressor will cycle all night with a low fan setting,,,,,,,,,,the 13000 BTU unit adds about 50 baht a night to my bill,,,,,,,,,,,the unit typically is on 8 hours. My living room unit which is 35,000 BTU will add about 100 to 125 baht for 6 or 7 hours and keep the room at 27 no problem. But due to poor insulation of the house I am sure I could do better,,,,,,,,,,rental house. If i switch off the living room AC within 30 minutes I have lost all the gain of running the air for 2 or 3 hours,,,,,,,,,,,,I use the living room AC only when really hot and sticky,,,,,,,,,,,,

................is IMO simply not true.

there will be a constant heat gain in the room related to the temperature differential between inside and outside and this heat is being sent back out again by the AC using electricity, albeit switching itself off and on, as long as it is itself switched on. How much insulation is in play simply slows the heat gain.

THere is of course a trade off. If you want the temperature to be cool the moment you walk in you better leave it on, but don't think for a second that you're not paying for it.

[longball53098]

Air Conditioning...

Okay this is probably a stupid question but is it better to leave the air conditioner on if you are out of the room for an hour rather than shut it off? Someone said to me one that turning it on and off all the time actually wastes more energy because starting it up consumes more than keeping it going. What's you opinion of this? Do your coworkers turn it on and off all day?

Computers...

What about computers as well are there any advantages to leaving them on?

Well I would say like all forums this post and the following replies got off the track a bit,,,,,,,,,,,,,,,,,you asked about AC and indicated "coworkers" in the question. So you clearly are asking about a work/office not a home.

So,,,,,,,,,,if your not paying the bills and no one is asking you to save money,,,,,,,,,,,,,,,,,I would say for "an hour" its not worth shutting it off as the electric cost is minimal. If you are trying to save a litre of oil or a bucket of coal,,,,,,,,,,,,,never mind,,,,,,,,,,,,,,,if your trying to save the planet? Good luck,,,,,,,,,,,,,Al Gore got the "Nobel" already.

Better idea,,,,,,,,,,,,,,,,shut the whole office down and head for the beach,,,,,,,,,,,,,,,,,,use the money your saving at the office to buy a chest full of ice and beer and pay some sweet thing to get a big hand fan and fan it over the ice chest,,,,,,,,,,,,the cold air will keep you cool and you have beer in the process,,,,,,,,,,,and a sweet young thing to look at.

Edited November 1, 2007 by longball53098

[TheEmperorOfTheNorth]

Turn it off.

Both AC and Computer.

[Scott]

Ditto

Turn them off.

I turn my AC and computer off if I am going to be out of my room for more than an hour--which usually means if I am leaving the house. It seems to save money and it certainly adds to my sense of security knowing they won't be on fire when I get back.

[elkangorito]

It took me 6 months to convince my colleagues that it is more costly to turn everything off for an hour than it would be to leave everything on. This only applies to an environment where the room occupancy at any one time, ranges from a few people to many people.

The same goes for air conditioned classrooms. My colleagues were turning off the a/c for an hour & then turning it back on when the room was suddenly occupied by 30 to 40 people. Not only was the room uncomfortable, the a/c compressors never stopped running & the a/c never got a chance to get to setpoint.

Now the a/c's are left on so when the classroom is suddenly filled with 30 to 40 hot boddies, everybody feels more comfortable in a short amount of time & the a/c has a "head start" with the increased load.

[longball53098]

It took me 6 months to convince my colleagues that it is more costly to turn everything off for an hour than it would be to leave everything on. This only applies to an environment where the room occupancy at any one time, ranges from a few people to many people.

The same goes for air conditioned classrooms. My colleagues were turning off the a/c for an hour & then turning it back on when the room was suddenly occupied by 30 to 40 people. Not only was the room uncomfortable, the a/c compressors never stopped running & the a/c never got a chance to get to setpoint.

Now the a/c's are left on so when the classroom is suddenly filled with 30 to 40 hot boddies, everybody feels more comfortable in a short amount of time & the a/c has a "head start" with the increased load.

I most whole heartedly agree,,,,,,,,,,,,,,,,work areas where many people congregate or come and go,,,,,,,,,,,,,,,leave it on,,,,,,,,,,,,,,,,,the system must work extra hard to bring the temp down if you shut it down and wait til the room is occupied again,,,,,,,,,,,,,,not to mention the hot , sweaty bodies that are stinking the place up,,,,,,,,,,,,