If you're talking about window units you need to look at BTU's...
Example:
Split level ranch: Three bedrooms, living room/dining area, kitchen on the upper level. Den, rumpus room, laundry room on the lower level. Average sized rooms.
Window units needed: 3-5
Same example but forced air through out the home:
Have a reputable A/C tech local reputable company check your freon level, compressor or size of A/C unit.
There are many factors to examine, overall square footage of the home, regional climate, home insulation issues, personal 'chill-out' preference. Stuff like that. I've worked in a blast freezer for years so any temp over 68-70 and I sweat, drives my wife crazy...
One air conditioner alone will be inadequate to cool a large 5 bedroom home.
it probably doesnt make a convectional current around the room.
Yes will work on that size house.
If your air conditioner is set to cool and it is heating you have a broken thermostat.
I have a 2003 X type Jaguar and the a/c does not come on when it's 45 degrees outside. Why?
Air conditioner. One heats the interior of the house; the other cools it.
Since the home is two story a small indoor air conditioner will not be able to cool the whole house by itself. To get this home to be cool you will need to use a A/C system both upstairs and downstairs.
cool air
A ductless air conditioner consists of two main components. These are a unit mounted on an inside wall that delivers the cool air to the room, and a unit mounted on the outside of the house.
When you cool hot air, water condenses out of it. This water should be piped to the outside of the air conditioner unit and drained away outside. It is possible that the drain pipe is blocked.
a air conditioner an cool you down
What do you mean by cool off period. Do you mean the time it takes to cool your house to the desired temp?