How to replace the plywood under the air handler

central-airdemolitionrepair

Sunday morning I walked out into my garage to find two huge water spots in the ceiling. The condensate drain line that comes out of my air handler in the attic had clogged up, and it turns out the contractor who originally installed the system didn't connect the secondary drain line to the drip pan. They ran the pipe for it and everything, but were too lazy to cut it and install a 90° PVC elbow.

It's been 10 years since the house was built, and Alabama's statute of limitations for construction work is 6 years – so having the original idiot that installed it come back and fix it isn't an option. Plus I don't want someone that daft touching anything in my house again.

I need to replace the OSB beneath the drip tray and air handler, since I found mold on its underside when I tore open the garage ceiling. I plan on placing two 2x4s beneath the air handler and lag bolting some hefty screw-eyes into them on either side, and then lag-bolting two more screw eyes into the roof joists above. Then I'll use two ratchet straps rated for the load to lift the whole thing a few inches off the plywood.

Next I'll demo the soaked plywood (I have underside access since I tore open the garage ceiling), slide some new sheets in, and screw everything down. Does anyone see a problem with this plan? Some concerns I had were:

  • How much flex will the refrigerant lines have? Enough to lift the whole thing several inches?
  • How fragile are air handlers typically? And how heavy are they? (I'm not sure what size mine is off the top of my head – it's a 1700 sq ft home.)
  • I may have to add some auxiliary bracing to the roof trusses if they can't handle the load. (They're 2x6s)

I've already had two AC companies give me a $3k quote for the work over the phone, and I have one guy give me a $1,350 quote after looking at the situation first-hand. first two want to disconnect the entire system to do the work, which I think is completely unnecessary. The third guy that gave me the cheaper quote said they'd just have to disconnect the trunk line. Am I crazy for trying this myself, or are they all just trying to rip me off?

Pictures:

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The drain that wasn't previously connected:

The drain that wasn't previously connected

Best Answer

You've got a fairly sizable amount of extra refrigerant line. Lifting your air handler a couple of inches will not be a problem.

The only part I would worry about is where the lines attach to the air handler. That's where the tightest bend radius is and you don't want to get that any tighter. But since you're going up, that should actually improve that bend radius.

You should be able to find the weight of the air handler by doing a search for the specs online. Find the model number and drop it in to Google. In general, they don't weigh too much; two grown men can comfortably lift a fully assembled unit.

One thing you might consider is to leave your air handler permanently suspended. But instead of 2x4s, get 2 heavy pieces of angle iron about 8 inches longer than the width of your air handler, 4 threaded rods, and appropriate nuts/bolts/washers. You can also get rubber bushings to put on the threaded rods to damp the vibrations from your air handler.

Slide the angle iron under the air handler where the wooden blocks are that currently hold up your air handler. Attach the threaded rod to the angle iron. There's two different ways to do that. One is to drill a hole in the angle iron but that might be difficult because of how hard iron is. The other is to use u bolts. If you go the u bolt route, you need to attach it carefully to the threaded rod so it can't slip out. Don't rely on compression to hold it. . A good plan would be 2 nuts with a lock washer in between and 4 or more large washers stacked on top. That will prevent the u bolt from sliding off the end.

To attach the other end of the threaded rod to your trusses, I suggest two 2x4s or 2x6s running perpendicular to the trusses the full length of the air handler, plus an additional truss bay on either side (this will spread the load across more trusses). Lag bolt the 2x4/6s to the trusses. Drill through the 2x4/6s for the threaded rods.

Here's a marked-up copy of your picture showing where everything goes. I outlined your air handler in black and grey (the grey is the hidden edges). The threaded rod is green and the angle iron is blue.

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