Central AC takes awhile to cool house down

Replace your air filter if you haven't already, and check the battery on your thermostat. That's what the HVAC guy tells me to do whenever there is a problem like this before having him make a service call.

1. how many sq/ft is the house and how many ton is the ac unit?
2. were you trying to cool it from 30c to 20c?

That's normal. Heat rises so it's natural that upstairs is hotter. Close any cold air returns you have in the basement to help the second floor returns work better.
Are your curtains/blinds closed to help block the sun/heat build up?

As above, what are you trying to cool down to? The A/C will first reduce humidity before it starts to cool. If the house is humid inside, the moisture has to be removed first. If you've left all the windows open and the air in the house is saturated, it will take more time. Obvious issue but one always has to ask the question: Are all windows and doors closed and shut tight?

If you can see where the coolant lines are, feel the two. If one is not cold (or at least much cooler than the other one), there may be something wrong. A clogged evaporator coil could also lead to the coil freezing and not being very effective.

For a typical sized house withe adequately sized A/C unit, don't expect anything more than cooling 1C/hour

When we turn air conditioners on for the first time after a heat wave, the humidity won't adequately be removed for 10-12 hours. Depending on how hot it is inside compared to how cool you want it

how do check what size is the AC? it came with the house since we moved in so i am not sure.

Battery definitely new since we just got a smart thermostat early this year. Also nothing too crazy, stat was reading at 25C. I assume that is the main floor read? Set it to 20C

We do have some old windows that prob needs replacing since we could feel a bit of draft during winter

The main floor will always be cooler than the 2nd floor and basement being the coolest in the house. The closer you are to the furnace the cooler it is. Trying closing all the registers on the main floor see if that makes a difference. Almost sounds like your AC unit may not be the correct size for your home.

Aznkid2000 wrote: ↑ how do check what size is the AC? it came with the house since we moved in so i am not sure.

Battery definitely new since we just got a smart thermostat early this year. Also nothing too crazy, stat was reading at 25C. I assume that is the main floor read? Set it to 20C

We do have some old windows that prob needs replacing since we could feel a bit of draft during winter

2-3 hours is not enough time to go from 25C to 20C. What temperature did it go down to after 3 hrs and why are you trying to cool to 20C?

If the upstairs is hot, you might want to look at attic insulation and see if it's adequate (can make a lot of difference). Also see if you can adjust the air return vents to favour the upstairs.

FWIW, 24C is perfectly comfortable once the humidity has been removed.

2-3 hours is not enough time to move 5C as others said. Relax and give it time. Check the filter and make sure all vents are open and the returns are not blocked. If things don't change then you might need to look further it call a tech.

Aznkid2000 wrote: ↑ how do check what size is the AC?

Go outside and look at the label on the AC. On there should be the brand and model number, along with the serial number. Usually the complete model number will include the size. For example, a 36000 BTU model may be labelled xxxxxx-036. That’s 3 tons (at 12000 BTU per ton). If you don’t understand how to read it, just post the brand and model number here.

However, knowing the size will be useless without knowing the square footage of your house and basement.

jackrabbit000 wrote: ↑ Ours is the same, takes about 2-3 hrs to bring the temp down from a 30C day outside to 23C inside. The upstairs is a lot hotter than the downstairs because heat rises. What I do is put a fan on the main floor and blow cold air up. It actually works pretty good for us and cools the upstairs down a lot faster. There is no way you can stand it in the house when I cool it down to 20C. I tried it once and it's just way too cold and it's like sitting in a freezer.

When we renovated our basement, we redid the ducting, but the biggest and most important change we did was to markedly increase the cold air return size from the second floor to the basement. That had a huge effect to help cooling of that second floor. For a lot of houses (esp. older ones), the cold air return is undersized since the HVAC system may be designed more for heating, not cooling, and they are counting too much on hot air rising on its own.

Close all your blinds. Get blackout curtains if necessary.
Consider installing reflective coating on your East/West facing windows. It's a quick, cheap DIY project that helped my house cool down a LOT. This:
https://www.homedepot.ca/product/gila-h ... 1000702560
Looks cool from the outside too, lol... it gives off that "mirror" effect during the day.
All my other suggestions have been covered by others above.

iEyeCaptain wrote: ↑ Close all your blinds. Get blackout curtains if necessary.

And better than blinds, this...

iEyeCaptain wrote: ↑ Close all your blinds. Get blackout curtains if necessary.
Consider installing reflective coating on your East/West facing windows. It's a quick, cheap DIY project that helped my house cool down a LOT. This:
https://www.homedepot.ca/product/gila-h ... 1000702560
Looks cool from the outside too, lol... it gives off that "mirror" effect during the day.
All my other suggestions have been covered by others above.

You have to be careful now with double-paned windows. There are quite a few manufacturers now that will void warranties for tinting windows because it cooks the inside of the window and the seals. There are indeed films that are double pane safe, but one has to be sure.

Aznkid2000 wrote: ↑ how do check what size is the AC? it came with the house since we moved in so i am not sure.

Battery definitely new since we just got a smart thermostat early this year. Also nothing too crazy, stat was reading at 25C. I assume that is the main floor read? Set it to 20C

We do have some old windows that prob needs replacing since we could feel a bit of draft during winter

Who installed the smart thermostat? Our smart thermostat was professionally installed incorrectly and blew a fuse in the furnace. In our case, the a/c would not come on at all. It was only through taking to the tech help with the thermostat and taking pics and sending them that they told us the install was incorrect. Luckily they told us which wires to change and which fuse to change so we were able to remedy it ourselves with their help.