Air Conditioners

[ruds]

Is it more cost effective to leave an air conditioner on all day or continually turning it on and off all day. I run a restaurant with 4 air conditioning units and the staff are constantly turning the air cons on and off. They tell me it is cheaper but I am not so sure. Anybody have any idea?

By the way the air con units are turned on and off about 6-8 times per day depending on the number of customers in the restaurant

Ruds

[MaximumSecurity]

My understanding is that it is less expensive to keep the room at a constant temperature. Going from very hot to cool several times a day is supposedly more expensive than staying at cool. In a restaurant especially where you have multiple cooling units, fridge, freezer, ice maker, they will consume much more electricity during the periods that the air con is off.

The best thing to do would be to read your electric meter in the morning, do a day of on-off. At night check the meter again, record the amount of electricity used. Then the next day, read the meter again at the same times, do an all day air con on, and compare the two usages. Just be sure that the outside temperatures were the same on both days, ie not one day rainy and the next sunny. Best if you keep an outdoor thermometer in the shade outside and write down the temperatures every hour to compare the two days.

Also, put some kind of shade, like a bamboo "fence" 15cm from the outdoor element of the air con. Keeping the sun off it can reduce electricity consumption by 30%. Be sure to clean the filters every 30 days.

[ruds]

Thanks for the response

[ozsamurai]

I think this one was tackled by Mythbusters in the form of is it better to leave your lights on or turn them off, the answer was turn them off

[way2muchcoffee]

I think this one was tackled by Mythbusters in the form of is it better to leave your lights on or turn them off, the answer was turn them off

What do lights and air conditioners have in common, beyond the obvious (they consume electric power)? Lights use electric power at a constant rate. Air conditioners consume power at a variable rate that depends on various factors, e.g. outside temperature, frequency of opening doors, temperature inside, number of heat-generating appliances used inside etc. MaximumSecurity had the best advice.

[JetsetBkk]

Doesn't make sense to me to switch it off while you need air conditioning. If you switch it off, the air will get too hot, so you switch it on again when you feel hot.

But that's what the thermostat is supposed to do!

I reckon your staff don't like the cold air, so they switch off the aircons giving the excuse about it being less expensive. Of course, it is less expensive but you (and your customers) suffer from it being too hot after it has been off for a while.

I think you need to ask your staff what temperature they would like the thermostat set at, and see if it suits the customers. If it doesn't... hard luck staff!

[0Mix1up]

it would also depend on the area being cooled.

is it open? have high ceilings, collect much sun during the hottest periods?

how much insulation? ceiling fans?

[tjo o tjim]

Short answer-- air conditioners are most efficient when loaded to about 70%. You can't manually watch how heavily loaded the air conditioner is based on space temperature-- just that it is overloaded (room getting hotter), or the thermostat is set too low (room too cold). You can put in controls to "stage" units to match load to compressors, but it isn't worth the effort.

The long answer is that shutting off the unit reduces fan energy and other parasitic loads. Letting the temperature rise in the space when unoccupied saves energy if your main load is skin load from the outside. Focusing cooling on only areas that need it can provide some savings in that perception of being cool is satisfied.

If you want to save energy, understand where the heat load comes from. If it is the open door... close it. If it is the roof... add insulation. If it is the kitchen... add ventilation. After all that is done, worry about the other stuff.

[dotcom]

I really think you are on the right track. Switching unnecessary air cons off will save money.

The reason being that you can cool the room down in a very short period of time.

I would purchase an old fashioned thermometer & affix it to the wall. Probably you will need one unit running all the time. But based on time of year, time of day - whether sun is shing directly on your windows you could add or remove additional units.

I would not let the staff be in charge of that. If you can keep the room 28 to 29 degress that should keep everyone happy.

Set the thermostats to 27 degress & admonish the staff that they are not to adjust them.

Merely stop or start units to maintain the desired temperature.

Be sure the filters are clean. This will rob you faster than anything else. Clean them one a week. If the aircon isn't ice cold while locked up (compressor running) get a service tech to look at it.

Everything needs to be really clean. inside & outside.