On Fri, 8 Sep 2006 21:45:10 -0400, "miamicuse"
wrote:

My central AC compressor unit is outdoor resting on a concrete pad. The pad
is 48"x48" in size and 4" thick and it is reinforced with steel rod. I
believe the pad is original so that will put it back to 1980 when the house
was built.

Recently the concrete pad started to fail. First a crack started about 8
inches from one edge, then more cracks along the outside edges, chunks of
concrete started to fall off exposing the rusted steel rods inside. The
compressor has four legs and it's bolted to the pad with concrete screws.
Of course with the pad failing two of the compressor legs will no longer be
resting on anything solid real soon.

Mine isn't bolted to the pad at all. I wish it were, becuase it keeps
moving maybe an eighth or fourteenth of an inch every year. Now it is
about 2 or 3 inches from where it was 27 years ago. (Maybe it moved
slower then and more quickly now. I don't know, and I'm not going to
mark it to find out.)

I'm afraid to put it back because I don't want to bend the pipes. But
it's only because I'm compulsive that I want to put it back at all.
It works fine.

Obviously I need to remedy this situation.

Do you?

But I have two questions:

(1) Is it normal for a pad to fail like this after 20 years? Why did it not
fail after 8 years or 12 years?

People always ask questions like that. Why did my tv break now? The
question and answer are above my pay grade.

If it waited 20 years, does it mean there
is some other factor involved? Like perhaps the soil below is yielding due
to a sink hole

That might account for a crack, but not for crumbling, afaik.

(house is in coastal south Florida sandy soil high water
table) or sewer line leak?

(2) If I replace the pad how would I go about doing it? I cannot just lift
and move the compressor aside which is very heavy and has very rigid
connections into the house's attic.

Right. That's why I'd consider doing nothing until you need a new
compressor, now matter how long that is. I'm serious.

Or, since I mentioned how compulsive I am, I might make a wood form,
and pour cement under the compressor, just to fill up the empty space
where it crumbled away. Same height as current height or if you go a
quarter inch higher than the base, no problem. You won't lift the
compressor, and when you need a new compressor, you can replace the
pad then, if yours is still breaking or not flat after your patch.

Al's idea sounds pretty good too.

IIUC only the parts beyond the steel reinforcing are falling off.
Even if it's worse than that, the bulk of the cement pad will be there
another 40 years. There is no special reason to think there is a sink
hole. Cement cracks and crumbles some times. The AC isn't going to
fall to the center of the earth -- it won't fall farther down at all
--, and if perchance it does, you can fix it then. I wouldn't go
looking for trouble.

After looking at your picture, I agree with myself even more. I would
remove the chunks that are an inch away, that have fallen off
completely.

And maybe paint the base, if you think that would make it nicer, and
before that you could put some kind of spackle in the crack, but
unless you want to make it pretty for guests, I'd just remove those
totally loose pieces.


A new pad will take a day have the form
done and the concrete poured, then a few more days at least to cure. I will
have to wait a while to put the compressor on again...do I get a concrete
repair place to fix this or the AC place to fix this?

Thanks,

MC