How to improve AC cooling efficiency?

I've noticed that my AC takes longer than usual to cool the house, especially on hot days. The air filter is clean, but the cooling still seems weak. What could be causing this, and what should I check first?

Try adding a sprinkler hose outside to cool the unit.

How old is it?  Could the problem be with the thermostat?

Anne Miller wrote:Try adding a sprinkler hose outside to cool the unit.

How old is it?  Could the problem be with the thermostat?

Water sprayed on the condensing coils outside is helpful, if you do not have hard water.  If you get deposits built up on the coils they will not cool as well.

If the unit is in the sun build a shade over it to help it stay cooler, but leave enough room for plenty of airflow.

Check your ductwork to make sure the connections are still secure and there are no leaks.

I definitely agree with getting shade on the unit.  It’s cheap and effective.  I personally like a wooden fence-like structure (broad, thin pieces of wood stapled together—it allows airflow but blocks almost all direct light).

Also. Consider some living structure (vines) climbing up a fence.  Just leave room for access and carefully watch for stuff that will fall into the unit.  An occasional hose-down and wash-out is also good.  It keeps the unit free from stuff that blocks heat flow and drops efficiency.  Also, make whatever light-blocking barrier you create big enough to block light from many angles.



Eric

I'd like to add that making sure your coils are clean is a good step. Funk can buildup and cause the unit to work harder. A good cleaning can be useful, especially on older units.

You may have a refrigerant leak and/or the interior coils are icing up.  Can you get to the interior unit and remove a panel to check the coils?  They might be dirty as well.

Gray Henon wrote:You may have a refrigerant leak and/or the interior coils are icing up.  Can you get to the interior unit and remove a panel to check the coils?  They might be dirty as well.

A few things that might indicate low refrigerant:
-Icing up (like Gray mentioned), either on the interior coil and/or the larger line between the inside and outside units.
-Feel the air blowing out of your outside unit, does it feel warm/hot, more-so than just outside air being blown? If not, then there's minimal heat being removed from the house, often indicating low refrigerant (assuming everything else is working properly).

Can you access ductwork in the attic or crawlspace, has something come loose or has a critter made a hole allowing air into an unconditioned space?

Check/clean both outside and inside coils (if accessible). Outside can just be a strong stream of water through the grill/louvers (the stronger the better, as long as you're not bending fins), assuming there's not leaves caught up against the coils. Inside can be tricky to impossible to access depending on the ductwork and air handler; you'll want to get at the upstream side of the coil, if there's buildup scrape it off with a plastic bristled brush in the directions of the fins.

If the unit is running but not cooling well then the thermostat is probably not the issue, unless it's badly located (blown on by a vent) causing it to cycle off and on.