Cold Air Trials

in the late afternoon on Sunday, the 29th of June 2008 by Chad

Friday night I noticed the central air conditioner doesn’t seem to be working well. A quick check on the thermostat shows that while it was set for 74, and running, it was 78 in the house. It’s never done that before.

I turned it off, waited a few minutes for the compressor to shut down, then started it back up again. Grabbed the infra-red thermometer and started checking vents. The same temperature was going in the returns as coming out. Not a good sign.

Checked outside, the compressor was running.

Went to the basement and found all the copper tubing coated in a thick coat of ice. That’s not right at all!

Seems the whole thing froze up on me. Now, air conditioners are supposed to cool the air, but making ice isn’t a good thing. Chipped off a good bit of the ice and I knew parts that should be warm were iced up also. The fan was also struggling to move the air.

So shut off the entire system for at least 24 hours to let everything melt. Luckily there’s a drain right there so no giant basement puddles for me.

Now, generally three different things could be the reason behind this.

Blocked air vents. Too little air flowing through the system is bad. You should leave most of your vents open, even in rooms not being used as often. If not, too little air circulates. I went around and checked and all vents were clear.
Leaking freon. This isn’t a good thing. Requires a visit and expensive coolant refill charges. Won’t know until everything has melted, and we fire it all up again. If it immediately freezes up again, then get on the AC contractors schedule.

Now, those are the major causes for 99% of the cases. Wasn’t blocked vents, and was hoping it wasn’t a leak. After restarting the system a few hours ago, and checking everything, my cause was the third reason:

The vent for certain types of humidifier was open.

Yeah, that’s what I did. The vent goes between the immediate exhaust back to the humidifier, and then back to the intake of the unit. This way in the winter, hot air will travel from the exhaust through the humidifier area, sucking up moisture, and then get cycled back through the entire system. In my case, cold air was immediately going back through the intake system. While no water was in the humidifier, there was enough humidity to slowly build up.

So after all that, I’ve got the nice 18 degree difference between the returns and the vents, and things are back to where they should be.