Home Improvement

See if you can spot any ice on the lines on the inside and outside unit. Chances are the coils are frozen. You will need to let it defrost if this is the case. Could take up to 24 hours. Or less than an hour of you run the heat. Be prepared for water to leak from the inside unit as the drain may not keep up. Once fully thawed (you'll never know when unless you can see inside an access panel, so longer is better) you can run it again. You should change the filter as low air flow can lead to frozen coils. If it happens again with a fresh filter, chances are it has low refrigerant and needs to be charged by an HVAC tech. If it's low after one year, you probably have a leak somewhere. Hopefully it's under warranty still.

Many good suggestions, but I didn't see anyone bring up how well the house is holding the temperature, aka insulation or leaks. The best AC can't keep it cool if that cool is going outside somehow. You say the vent air feels cold so it seems to be doing its best. Single pane windows, especially facing the direct afternoon sun will be hard to keep from undoing the cooling. Attic space that has little insulation will also defeat the efforts.

when this happened to me the heat exchanger inside was all iced up, turned out it was a valve in the circulation. Couldn't fix it myself due to compressed coolant.

As others have stated, replace your air filter if you haven’t recently. Make sure it’s the appropriate size and rating. It should probably be pleated, and the MERV rating shouldn’t be too high unless you know the fan supports it.

Use a temp gun or a kitchen instant read thermometer and compare the exhaust temp vs the return temp. It should be around 15 degrees difference or more. If it’s not then an installer should adjust the pressure on the system.

If you have multiple floors you may have a vent damper for summer vs winter. In the winter the dampers may be set to help force air through the lower floor vents and prevent the hot air from rising too fast to the upper floors. If the installer or previous owner was nice the damper will be labeled for summer vs winter.

If it’s not blowing air at all, then you may have a leak or a blockage.

If theres ice on the indoor coil or on the lines outside then either the filter is clogged or your pressure is off.

If your hvac person is telling you it’s working fine and it obviously is not, call a different installer.

1400sqf = 130m2

Typically in Australia we’d size for 180W/m2 which in a domestic setting gives plenty of heads room.

130x180 = 23.4kW unit. This size it would be a ducted unit to ensure proper distribution of cooling throughout.

2.5tonne equates to approximately 8.8kW which only gives you 68W/m2 which as an ex mechanical engineer is completely undersized at least for Australian summer.

Without knowing more the only suggestion I would give is set the target temperature a bit higher. This increases the units efficiency and should help it get to temperature quicker.

If you’re uncomfortable try running an additional fan. The movement of the air will make you feel cooler even if the air temperature is the same.

Has it been working alright throughout the rest of the season? I had an HVAC system that was incorrectly wired by the installers, so it actually ran the AC and heat pump at the same time, cancelling each other out. Might not be your situation but you never know!

2.5 tons is right in the edge of being able to handle 1400 sq ft. Where do you live? It is two story or one? I think your AC might just not be about to keep up. Nothing wrong with it.

The other posters have given good info. I just wanted to add to try setting the fan to on instead of auto so it runs all of the time. This will help keep the air moving in the house and might help keep it cooler. Also make sure you check the filter and change it if you haven't yet. See if your energy company offers an energy audit. that will tell you if you have leaky windows, doors, or insulation problems. I have shitty insulation but with the ac fan running all of the time I can keep the house @ 70 - 72 on a 95 degree day.

I'd also consider getting a second opinion from another HVAC company, you could have undersized ductwork or another problem that the first company isn't acknowledging.

Have you replaced your filter recently?

Does the unit have a standard 1" thick filter or a thicker one?

Could be a refrigerant leak. It will still run but won’t cool.

Take a look at your return register. I was having this issue at the beginning of the season and my return had some pet hair lodged in it. That coupled with a new filter (and for the return if it uses one) should help keep the temps down.

I'm a layman but from what I've read recently, 92 to 78 is 14 degrees; the typical temperature differential is a maximum of about 20. There may be a few more degrees you can eke out, but you are getting a majority of the potential benefits

I'm surprised no one mentioned this so far: check to make sure the fins on your outside unit are clean.

My parents had this issue when I was visiting. I went outside and looked at their unit and it looked like it was covered in carpet. I took a hose and gently rinsed off all of the dirt and pollen and they were back in action.

Others already covered a lot of good points: make sure it's not froze (it likely is if you've been running for a while and it's not keeping up) and change the filter.

If that doesn't work you likely need refrigerant.

leaky ductwork is often a source of efficiency loss. i found a disconnected section of ductwork in my attic. Fixing that was a huge help.