Faulty Logic Re Air-Con Use?

[JusMe]

The days tend to be warm, and the house gets warmed up. For some reason, it holds the heat when outside cools in the evening.

I've noticed that outside is comfortable, maybe 24~26°C, but the thermometer on my clock in the bedroom will show 31~32°C, even with open windows.

Now, if I turn on the air conditioner, set to 27°C, it cycles through the fan and cooling. The fan is on all the time, pleasant, but the actual cooling is on and off for some time, as the room slowly cools, although never right to the set temperature.

Leaving those windows open, the air-con will cycle the fan, which is pleasant, and the cooling until it gets to the set temperature, which is actually higher than the outside temperature. So even if there's some transference of air between inside and outside, the unit won't be trying to cool the entire atmosphere.

The fan alone won't cost much to run, and if the cooling isn't on all the time, that means a reduced cost, doesn't it?

So, anything wrong with the logic of turning on the air-con overnight with the windows open?

[bankruatsteve]

If you are happy with the ambient temperature, then all you should need is the fan (mode with the A/C unit or ceiling or whatever). If you want the A/C to cool below that, then set the temp lower. Not sure where the temp is measured on the A/C (although I think that has been discussed in this forum previously) but I also notice a difference in my wall thermometer and the cycling down of my A/C (about 2-3 degrees diff.) For me 26 is the feel good setting for my A/C

In any case, I see no "logic" to running the A/C on cool with the windows open.

[ETatBKK]

may confuse the air con sensor while switching on the air con with windows open.

Japanese and Korean way of using air con + fan solution : 15 to 30 minutes before sleeping, switch on the aircon and cool the room a bit, a fan next to the window and draw fresh air in. the aircon auto off after 1 or 2 hours.

you won't get too cool at the middle of the night.

[electau]

Close all windows and door , set thermostat to 25C ( this is the return air temperature). start aircon about 30 minutes before room is to be used. 27C is known as the economy setting, min power consumption. For every degree C below 25 will increase electricity consumption by about 10%, based on a 2400kW (cooling not input kW).

You will not cool your room with the windows open.

[Morden]

We don't have or want air con. at home. It dehydrates the body. In the car, on a plane or in an hotel room it's essential but living with it at home is too much for me.

We have doors permanently open with bug mesh and security doors to keep out unwanted visitors. That allows air to move through the house. When that's not enough, we turn on ceiling fans to move the air around.

To use air con. effectively, you must almost seal the house to avoid air loss to the outside. That seems to indicate that you are heating up the house by shutting it off, only to pay for electricity to cool it down again.

[JusMe]

We have doors permanently open with bug mesh and security doors to keep out unwanted visitors. That allows air to move through the house. When that's not enough, we turn on ceiling fans to move the air around.

I have that with doors open all the time, screened, and the ceiling fans running, but for some reason I just can't get the air exchanging between inside and outside. The inside with doors and windows open and ceiling fans running is still much warmer than outside.

I could be misusing my air con unit, as I admit never properly learning how to adjust it other than turning it on and off and raising or lowering the temperature setting. Unfortunately, no comprehensible manuals.

I do notice that it seems to cycle between fan and cooling, with a change in temperature blowing, noise level, and the single or double green light glowing. That's why I was wondering about using it with the windows open so that the cooling would only drop the room temperature to the outside temperature, and then only the fan part of the unit would work.

[mrbojangles]

Do you have any method in place for venting the roof space? I don't know the exact economics but for a very small amount of baht, having your roof space vented and drawing out the hot air that has built up during the day with some small extraction fans, makes a huge difference.

[Morden]

Do you have any method in place for venting the roof space? I don't know the exact economics but for a very small amount of baht, having your roof space vented and drawing out the hot air that has built up during the day with some small extraction fans, makes a huge difference.

Good idea.

In Florida, the bungalows are often built with cathedral roofs that extend from the sitting rooms up into the roof space with a vent for hot air in the roof.

[JusMe]

Do you have any method in place for venting the roof space? I don't know the exact economics but for a very small amount of baht, having your roof space vented and drawing out the hot air that has built up during the day with some small extraction fans, makes a huge difference.

I've got some venting there, as well as insulating blanket across the roof tiles to reflect the heat back outwards. Even touching the ceiling inside it's barely warm, let alone hot, so I think that's working. No heat coming in from the ceiling.

[TS79]

Air Con units generally have a setting where only the fan is operational and not the cooling side of it. Doubt it would have much effect in drawing in the outside air though.

Better to place a floor standing fan by the open window or door so it pulls in the outside air.

[wpcoe]

Sorry I can't credit the original poster of this link as I can't find the thread right now, but in that thread s/he discussed using these relatively inexpensive exhaust fans to remove heated air from the room, commenting that the volume of air moved was sufficient to noticeably tug on a door when trying to close it.

Maybe such a fan in each room's ceiling with the door closed and window open would help bring in the outside cooler air? Perhaps the problem you have is that just passive convection of heat through an open window isn't enough, you need more active air flow into the room from outdoors.

Almost forgot: here is the link. If my reading is correct, the 19-watt fan moves 460 CMH (cubic meters per hour?)/271 CFM (cubic feet per minute?) which is considerable. My only concern would be how quiet the fan is.

[Morden]

Sorry I can't credit the original poster of this link as I can't find the thread right now, but in that thread s/he discussed using these relatively inexpensive exhaust fans to remove heated air from the room, commenting that the volume of air moved was sufficient to noticeably tug on a door when trying to close it.

Maybe such a fan in each room's ceiling with the door closed and window open would help bring in the outside cooler air? Perhaps the problem you have is that just passive convection of heat through an open window isn't enough, you need more active air flow into the room from outdoors.

Almost forgot: here is the link. If my reading is correct, the 19-watt fan moves 460 CMH (cubic meters per hour?)/271 CFM (cubic feet per minute?) which is considerable. My only concern would be how quiet the fan is.

Keeping a room door open as well as a window helps circulation. Warm air moves upstairs at night so we allow outside air to follow it through downstairs windows and doors, up the stairs and, with the help of a ceiling fan in the bedroom when needed, pass out through open windows there.

[Naam]

this thread should be renamed to... err... i withdraw my suggestion. reason: it might violate forum rules.