It's gettin' hot in herre...

August 19, 2008 8:41 AM

Help me keep cool! Ok, I'm a bit OCD about this I realize. I'm wondering if there's some way to test the AC in my apartment to see if it's working properly. Is there a special thermometer to use to test the air temperature coming out of the vents? If so, what should that temperature be?

A little background: I live in Austin, TX. It's very hot. We've been on a tear of triple-digit days so naturally ACs will have to work harder to keep up, but even after the sun goes down it seems to take my air conditioner forever to bring the temp down just a little bit. It seems to run all night. When I wake up it is definitely cold in my place but the AC is still running. It might stop for a couple of minutes and then start up again. When it does catch up and stop it only stops for a couple of minutes before going back on. They recently had to rip up my ceilings to get any air flowing out of the vents in my kitchen/dining area b/c the ducts had been crushed or something. Now there's a tiny amount of output in the kitchen/dining area and a disproportionate amount of air output from the vent in my living room. My first bill was 120 bucks… not great but unreasonable unless you consider I spent half of the month (maybe a bit over half) at my girlfriend's apartment with the AC turned off completely. Extrapolating my utility bill rate over the course of an entire month it would have been over 200 bucks. I think over 200 bucks for a utility bill for a one bedroom apartment (under 700 sq. feet) would be absurdly high, right? My concern is that maintenance, which at this new place is notoriously slow and lazy, will just say "it's working" and do nothing even if there's not enough coolant because what do they care what my bills are? Is there any way to prove that it's not working properly? Anything I can do myself to make it run better? Should I call my own AC guy out to check it out? If the vents aren't blowing cold enough would a simple "charge" of the coolant work to fix it? They did clean the coils but I don't think that did much.

posted by odayoday to home & garden (8 answers total)

It sounds like you need to get a third party to come check out your AC unit to see if everything is working properly. Or, you could threaten your new place (I assume you're renting) to get some action on it or you'll go to a third party and bill them for the repairs.
posted by wangarific at 8:46 AM on August 19, 2008

I hate to point out the obvious, but the temperature coming out of the vent should be COLDER than the air going in (or otherwise in the room). Air conditioners don't pull air from outside of the building, they just recirculate air internally (not always the case for large scale HVAC systems mind you).
posted by SirStan at 8:50 AM on August 19, 2008

Is there any way to prove that it's not working properly?

The way I've seen home inspectors measure AC effectiveness is to let the room heat up, then turn on the AC unit high enough that it runs constantly for about a half hour. Measure the temperature near a vent before and after, and the differential should be around 16-22 degrees.

Also, modern AC units are much more energy efficient than old ones, so getting a brand new AC unit would most likely save you large amounts on your electric bills.
posted by burnmp3s at 9:04 AM on August 19, 2008

In my office, we've checked the vent temps with digital, infared thermometer. Not sure which particular one is used. Nifty little gadgets though.
posted by kellyblah at 9:27 AM on August 19, 2008

You can use a regular outdoor thermometer and measure the temperature of the air going in the intake vent, then measure the temperature of the air coming out of the register. (Actually, you should stick the thermometer in the intake and registers to take the measurements). The difference should be about 20 degrees.

Your bills do seem high - that's about what I pay to cool my 1300 sqft house in Austin. You should also check that you have a good adjustable/programmable thermostat, check that your filter is new and changed often and that the outside unit is clean and has free air flow around it.

The other dangers are that there is a leak in the ducts - basically cooling your attic space.

Good luck and hopefully the worst of the summer is behind us...
posted by nightwood at 9:30 AM on August 19, 2008

I live just down the road in San Antonio and $200 for a month cooling a 700 sq ft apartment is exactly what I have too. I live on the second floor though and I think the insulation is really crappy. I guess I live with it and offset it by not having to ever heat the place.
posted by sanka at 9:32 AM on August 19, 2008

Call an HVAC specialist and ask them to inspect/service it. Our AC coolant leaked in our house two weeks ago, causing thousands of dollars worth of water damage to our house. You do *not* want that happening. Ounce of prevention & all that.

Also, do you replace the filters regularly? This can have an impact on the unit's efficiency.
posted by media_itoku at 11:54 AM on August 19, 2008

Maybe you have a leak.

When we moved in, the cracks around the windows were really bad. In the winter when we put that insulating plastic over the windows you would see it balloon out. In the basement, where some of the pipes went to the outside through the foundation you could see daylight from inside the basement.

At some point, one of the genius previous owners decided they needed extra storage space in the attic, pushed all the insulation to one side and nailed plywood over the joists to make a flat floor.

We also had a leak in one of the ducts in the basement. Someone had turned a damper knob too hard at some point and both ripped off the knob and tore a hole in the duct. The result was it was super cool in the drop ceiling in the basement.

All these little things add up without being all that noticeable by themself.
posted by monkeydluffy at 3:49 PM on August 19, 2008