Thursday, July 8, 2010

What's old is new again: Home Improvement Edition

Regarding yesterday's A/C fiasco, I dialed up a number from the Good Ol' Boy network to ask an electrician buddy of mine about what he knows about central A/C units. Electricians know probably more about the HVAC trade than folks in any of the other trades combined, and even that knowledge is extremely limited.

You HVAC boys have that market shut like a lock.

My buddy didn't have much information for me other than he would come over and help me in any way he could. Meanwhile, back at the ranch, SailorCurt dropped me a comment with a link to a post he did on fixing his A/C unit. I read that post several times.

Could these frickin' things be that simple? I've set dozens of A/C units on the pedestal, leveled them, and then wired them up, but I've never really looked inside of one. The voodoo involved in making them work is the specialty of the HVAC boys; they go down deep within the heart of these units and add magic potions mixed from elven babies blood and unicorn tears. The units themselves are expertly forged by the hands of mighty dwarfs, crafted from the finest aluminum hewn from inside the Stickitooomeee mountains. I just envisioned them being so complicated considering that they cost thousands of dollars, they have to be installed by experts licensed. . . LICENSED!!. . . to add the magic potions, and some of them are even powered by trains that you can't even see! Nothing can stop those ones.

So imagine my surprise when I opened mine up and found out that Yup, it's just a run-of-the-mill compressor with a radiator like thingy surrounding it, and a simple motor with a fan. A consult with Google-The-Wise showed that the HVAC boys affectionately refer to them as "squirrel cages."

I've got it now.

Armed with SailorCurt's post, and my new found confidence that I can swap out a motor and make it work as long as the compressor is still good, buddy and I set about to make my world a better place. Good buddy noted that he had an A/C unit that the Direct TV installer had climbed on and broken, but that the fan motor and capacitor were still good to go. It was about five years old, but had only operated for a few weeks when the incident happened. Basically it was all brand new, but would it fit?

Like a glove!

Now the only problem I had was that the new fan spun the wrong way; the 3-blade fan that came with the new motor was too big, and the 4-blade fan that was on the old motor was pitched the wrong way. New motor with old fan went into the A/C unit, and managed to get my house down from this, taken last night:

To 81 degrees this morning. I went out to check on things this morning and the A/C was kinda milling super hot air around the unit, instead of blowing it out the top. These A/C thingies are really pretty neat; the fan pulls the coolest ambient air around (the air closest to the ground) through the coils (radiator looking doodad) and up out the top, all while also drawing the super hot air around the compressor (at the bottom of the unit) out the top with it. It's like the radiator in your car, only with the fan on top of the motor blowing the hot air out a big vent in your hood. Smart!

Thinking about it last night, I realized my remedy was to cut the thin aluminum blades of the fan that was on the new motor. Measuring carefully and guiding the Sharpie along by edging my fingers along the curved end of the blade, I marked off about an inch and a half of blade which was easily scored by a razor knife. The cut part peeled right off just as pretty as you please. The fan's hub is steel, and I didn't mess with it. One thing to know is that the fan is balanced, so cutting it runs the risk of making the whole unit wobble when it spins. Mine now has a barely perceptible wobble, which I can fix with the counter weights from my old fan. . . .on a cool day; it's good to go right now. When I fired it back up this morning, I could see it draw the ambient air through the sides of the unit like it's supposed to, and hot air was blowing right out the top.

All should be well now!

My kids were up until close to midnight last night, and everyone was in a foul mood from the heat. We had little room fans set up all over the place to make sure there was some circulating air, but it was still miserable. The bad part about it is that all of this could have been prevented with a little preventative maintenance.

The reason the old fan siezed up is because one of the two 125 volt lines that feed the motor had long ago come loose - long enough that the exposed copper was slightly corroded. The fan, running on half power, and with a full load from struggling against the heat wave on the East Coast, over taxed the capacitor, which was visibly bulged when I took off the electrical panel cover on the A/C unit. If I had shut the power off and looked over the daggone thing this spring, I probably could have avoided the whole fiasco entirely. Just the same though, ordering a new motor and capacitor costs less than a hundred bucks, which is way better than calling Home Despot to send out a barely trained installer to replace your A/C unit for $5,000.

Some things can be done yourself.

I'd like to give a big thanks to SailorCurt for his very helpful post! I really appreciate it!


Anonymous said...

You're more than welcome. Posts like that one are kind of selfish in some ways, because I get to enjoy the nice, warm, fuzzy feeling I get when someone tells me they found the post useful.

Helping others is what it's all about...otherwise, what's the point?

Anonymous said...

Odd. When I replaced the fan motor on mine a few years back, it also ran backwards. I switched the polarity of the capacitor (switch leads - GROUND each side with a clip lead first!!) and it ran the correct way. That capacitor is a starter cap and is polarized.

Cheers, Cactus Jack Poltroon

Unknown said...

"Helping others is what it's all about...otherwise, what's the point?" - Absolutely. And would you ever have thought that your post could save someone thousands of dollars?

"That capacitor is a starter cap and is polarized." - I thought it might be, but was happy enough with what I had going to risk potentially burning up the only motor I had at the time.