Monday, May 15, 2006

Slingshot AC

Those of us who live in older (meaning poorly insulated) homes in AZ know all about slingshotting your AC.

What is this you say?

Well its when you deliberately overcool the house in the morning so that by the time 2-4 o'clock rolls around your AC can maintain the 30-50 degree temperature differential necessary to keep comfy in the summer heat here.

You see, once the temps climb over 100 (every day the past week we've at least touched it in my neighborhood; we've been up to 104 so far this year), even the most powerful newer AC systems just have a hard time keeping up in a poorly insulated home; which unfortunately includes most homes in Arizona. The AC systems end up having to work on a 100% duty cycle which causes them to do not nice things.

Once of those not nice things is freezing up. This happens when you aren't moving enough air over the heat exchanger coils. The coils do a bangup job of cooling the air immediately around themselves well below the dew point, and the small fins in the heat exchanger box build up ice dams in between them, which blocks airflow even further, accelerating the process.

The reason why there isn't enough airflow? Well thats one of those other not nice things that happens with a heavy duty cycle. The air here has a lot of dust in it. Even better, theres random floaty fibrous stuff from various plants and animals. And of course there's the smog particulates etc... All of these components build up in your ducts and on your furnace filter. Eventually air jsut stops moving, which causes the pipes to freeze, and you to bake.

Oh and when this happens a third not nice thing starts happening which is endemic to the area, mold grows within minutes (wet ductwork is BAD).

So today wasn't all that hot (it just barely touched 100, then the clouds came out), but it was a bit more humid. Around mid day I started noticing it was a bit warm, but I figured "Ahh it's nothing, the AC must just be set a couple degrees higher than normal" normal being 74.

When it hit 80 degrees in my usually cool bedroom I was getting irritated, and I went and put my hand up over a vent. Sure 'nuff nothing.

First things first, turn it to heat and see if I get anything...

Nope, hot air, but almost none of it. This of course means the air handler is clogged up; either at the filter, or its frozen up, or both (most likely both since it was a few hours before I caught it).

So I pop open the furnace cover and check out the furnace filter, and it's COMPLETELY clogged. I mean there is NO way air could have gotten through there. I dont know why we didnt notice it before, but it's BAD. Thankfully it's also washable, and I took it out and hosed the bad boy off.

I also left the air handler cover off and turned the heat up, to melt the ice dams that had built up in the handling box.

It took about 30 minutes, but we finally started seeing some cool air again. In the mean time the house had gotten up to 89 degrees.

That was two hours ago, and the AC is doing a valiant job (and the vent air speed is much more noticible), and has managed to take us down to 79. It probably wont be able to get much further ahead til the sun goes down in another hour or so.