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Help my air con wont go under 25

tony kop77

Well-known Member
I have had my air con for about a month and when I first used it my room got down to 18 in a few hours but now in this heat it wont go under 25 unless it is about midnight and even then it will only got to around 22.
I have to have the window open slighlty so that I can put the pipe out of the window and I have the curtains closed is there anything else I can do to get the room temp down?


If you can seal the window opening better with a cardboard or hardboard or plywood filler that will help. Is it upstairs? if so, try more insulation in the loft over that room. Get the unit as close to the window as possible to minimise the hose run. The outlet hose will leak a lot of heat into the room, so try insulating it with a hot water tank jacket. There is a chance that the air conditioner has developed a fault, but you can only test that once the hot spell is over to see if it behaves as before. Most likely it is fine but only capable of lowering the temperature 5 degrees.


tony kop77

Well-known Member
Thank You, I thought it would still get the room down to 16c like it did the other week. The air con is in my bedroom just belowe the window, the problem with the window is it is quite a big side window and I can't really seal it to stop the air coming in.
The air con I have is this one if it helps http://www.homebase.co.uk/webapp/wc...001&langId=-1&catalogId=4551&productId=232603

Power resource 220-240V 50HZ
Max Input 1100W
It got a B grade for electrical expense so do you think it will be expensive to run? I was hoping it would not cost more than 50p an hour.


Well-known Member
It's going to use just over one unit per hour (1100W = 1.1 kW/h = 1.1 units per hour) running flat out. The cost of a unit depends on your supplier and tarrif, but is probably around 12p.


Standard Member
As already said you need to stop warm air coming back into the room. The fact it is not working as well will probably be due to the higher temperatures and also the humidity levels. I think these units work by extracting heat from the air as it passes through a heat exchanger in the water tank, the warm air from the tank is then passed outside. Im not sure if you could try using colder water in the tank, and maybe change more often to try and increase its cooling capacity. You also need to make sure that all filters are as clean as possible to make sure the airflow is not restricted. The biggest difference will be to insulate the room/window as much as possible though.


Active Member
with the high temperatures we've been having it's simply a limitation of the 'vent out of a window' type system. All that air that's being blown out the vent pipe has to be replaced with outside air (unless you want to suffocate;) ) so the air being drawn into the room will be hot.

The only use I've found for them is to have the cold air blow directly onto you - at least that way you get some benefit. Other than that, buy a proper split unit aircon where the condensor is on the outside and the evaporator can cool the same air in the room without actually removing it.

Kevin W.

PS>> No water involved in a Air conditioner (Don't confuse it with a Air Cooler). Air con works the same way as a fridge - refrigerant gas is pumped around a sealed system with a condensor and an evaporator (and a couple more bits). Air is drawn across a large sufrace area condensor and due to the evaporate effect the gas is cooled (In an all in one this hot air is expelled via the vent pipe) Air is then passed over a smaller surface area unit called the evaporator where the air is cooled and passed into the room.

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