Building a Base for Split AC Compressor

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  #1  
Old 06-02-15, 08:20 AM
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Building a Base for Split AC Compressor

I am putting a split system AC in and I planned to secure it to the foundation of my house. But the brackets I got are too long. They are intended to be installed in an "L" instead of a "7" The vertical piece is 20 inches long.

My house has the foundation come up 2 feet and then there is vinyl siding above that.

If the brackets were to be installed as a "7" then the vertical piece would bolt into the foundation and all would be well. But as an "L" the vertical piece would need to be on the vinyl in order for the horizontal piece to sit above the ground by a foot or so , which is what I am looking for.
I dont want to attach to the vinyl part because I wont even know where the studs are.

So I figure I can cut the vertical piece with a hacksaw and take 10 inches or so off it. Then I can attach it to the concrete and my unit would still be raised a good foot off the ground.

But, I could also just build a simply platform on the ground. The only concern is that I havent seen anyone do this in all of my research. So maybe there is a reason why?

I figure I could stack pressure treated 4x4s in a box shape, 3 or 4 rows high, which would give me my 12 or so inches. It seems so very simple but I have never noticed anyone do that.

Would there be too much movement as the wood dries out? I know these tend to warp sometimes, but my lengths would be pretty short (the box would be about 3'x2') so I wouldnt expect too much warping.

Any thoughts on this?
 
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Old 06-02-15, 09:49 AM
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Why would you want to attach it to the foundation?
 
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Old 06-02-15, 10:14 AM
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I want it off the ground, about a foot or so, and it just seemed from the images I saw during all of my research that it was a common option. I didnt see many platforms unless they were just a layer or two of brick.

Maybe I saw the images and just got biased early on and just kept working with that in mind.

So, does a raised platform from 4x4s make sense? Still wondering why I dont see much of that.

I see a lot of this: http://www.google.com/imgres?imgurl=...d=0CFEQMygqMCo

and alot of this: https://encrypted-tbn1.gstatic.com/i...JElgoKgZuzYeFa

I was planning on something like this, just a bit higher: http://i.ytimg.com/vi/59VCjwEWGQQ/maxresdefault.jpg
 
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Old 06-02-15, 11:08 AM
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Oh OK, your installing a mini split, now it makes sense. That's to keep it above the snow line. So I assume this is heat pump?
 
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Old 06-02-15, 11:13 AM
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Yes, sorry if I wasn't clear. That is exactly the reason. It is a heat pump as well as AC.
 
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Old 06-02-15, 11:38 AM
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Most Pro's would not use wood. They wouldn't want the liability. I would find a way to mount it to the foundation. What is your snowfall like?
 
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Old 06-02-15, 11:47 AM
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I am on Long Island. So we can certainly get a foot or more a couple of times a year.

What would be the liability with wood?

I could also build a small brick or concrete block base.

If I go with the brackets I will need to hacksaw part of the vertical piece off so that it fits.
 

Last edited by rmathome; 06-02-15 at 12:05 PM.
  #8  
Old 06-02-15, 12:42 PM
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As long as the bracket doesn't have a diagonal brace that would be compromised by shortening the vertical leg I would go ahead and shorten the vertical. I would use nothing less than two, 3/8 inch concrete anchors (three might be better if you have the room) through the vertical and into the concrete wall on each bracket.
 
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Old 06-02-15, 01:13 PM
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Do as Furd says, or you should be able to buy a ground stand at any HVAC supply shop. 95% of the ones installed in my area are on ground stands so as to eliminate any vibration noise from coming through the wall.
 
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Old 06-02-15, 01:45 PM
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there is no diagonal. Can I ask why cutting them brackets is better than making a base?

Also, what depth screw would you use and what would you use to anchor it into the concrete? I know there are different types of shields but not sure what would be best.

I shouldnt get vibration if it is attached to the foundation, should I?
 
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Old 06-02-15, 02:01 PM
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I like to use Tapcon screws, no anchor necessary.
 
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Old 06-02-15, 02:15 PM
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Someone once told me that Tapcons dont work well in old concrete (this would have been poured in 1950 or so)

Is there any truth to that?
 
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Old 06-02-15, 02:28 PM
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I don't think so, i think the older the concrete the harder it is.
 
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Old 06-02-15, 03:54 PM
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I was thinking on my drive home how much easier it would be to make a base out of a couple of 4x4s.

Why would that not be the right way to go?
 
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Old 06-02-15, 05:03 PM
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Too much potential for movement and a subsequent leak with a wood base. It could be done if it were built very solid, but just stacking a few 4x4 on the ground wont cut it.
 
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Old 06-02-15, 05:29 PM
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Go ahead and build the base out of wood. Sitting directly on the ground they will be subject to rot and insect damage as well as possible frost heave when the ground freezes. In addition, when the unit is in defrost mode it will spill water all over the wooden base. All of this will tend to limit the life of the wooden base. If that doesn't bother you then go for it. The problems will come home to roost when you need to repair or replace the wood because then you will need to support the unit with minimal movement in order to NOT break the refrigerant piping.

In my opinion Tapcons are not sufficient to bolt the brackets to the foundation wall. As I stated earlier, nothing less than two, 3/8 inch bolts, either wedge type or expanding shields, per bracket. Do it right and do it once.
 
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Old 06-03-15, 07:49 AM
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With the exception of heaving, wouldnt pressure treated wood avoid all of the other issues?

I guess the way to do it on the ground would require a proper footing? Dug down below the frost line?

Regardless, it sounds like you are in favor of mounting brackets as the best overall solution.

Does that bring with it a chance of vibration? Im guessing not much of a concern when mounted on a foundation (as opposed to the side of a house, like the sheathing)
 
  #18  
Old 06-03-15, 05:24 PM
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I've never known a mini-split condenser to vibrate much but if you are really concerned use vibration mounts between the unit and the brackets or platform.

https://www.google.com/search?q=vibr...utf-8&oe=utf-8
 
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Old 06-03-15, 05:29 PM
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If neither the unit or the brackets came with vibration mounts, I guess it is safe to assume there wouldnt be much to worry about?
 
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Old 06-03-15, 05:33 PM
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The amount of vibration you get depends on the size and quality of the unit, and the composition of the wall. On a concrete wall, there should not be any noticeable vibration.
 
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Old 06-04-15, 08:19 AM
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Use pump ups this will get it off the ground http://www.americanhvacparts.com/p-1...-3-height.aspx
 
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Old 06-04-15, 08:22 AM
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Caddy brand make it any height CADDY® PYRAMID Equipment Support Kit
 
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Old 06-04-15, 08:57 AM
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That is an interesting looking support. But I would think that I would have the same potential heaving issue as wood, or anything else just placed on the ground... no?
 
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Old 06-05-15, 08:30 AM
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Wood rots and will shrink and could bow. The plastic and rubber will not.
 
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Old 06-06-15, 09:00 AM
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pressure treated wood doesnt rot, does it?

And a 3 foot length of 6x6 wouldnt bow--could it?
 
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Old 06-06-15, 11:38 AM
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Pressure treated wood does rot, it just takes longer.

It sounds like you have committed yourself to building a wooden base despite all the recommendations here not to. Just make sure it is solid. You should be able to rump up and down on it without any chance of movenment at all for it to even be close to stable enough. Frost heave is going to be your biggest issue.
 
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Old 06-07-15, 07:44 AM
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It sounds like you have committed yourself to building a wooden base
No, I just want to make sure that I make the best decision. And I just dont feel like I have all of the answers on both options.

Wood seems easy, but not as easy to get level and keep level.

I even considered pouring a concrete pad but... well now I think Im going overboard and making more work than is necessary.

The wall mount seems easiest to get level and secure, but what about vibrations? Will my entire foundation be vibrating?
 

Last edited by rmathome; 06-07-15 at 08:53 AM.
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Old 06-07-15, 10:56 AM
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No, your foundation will not be vibrating and neither will the heat pump.
 
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Old 06-07-15, 07:42 PM
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ok, brackets on the foundation it is.

Now, a couple of other questions if it's ok (not about the base)

1) On the inside unit--which is already installed--it is not sitting flush against the wall all on both ends. On the right side it is flush, but on the left side it is about 1/8 away from the wall. So, looking at the unit from the bottom, the right side touches the wall, then as you look toward the left side, it gradually comes away from the wall so that by the time you are looking at the left end, it is off the wall a little just a tad.

The metal plate was, as best I could tell, flat and perfect against the wall. And the wall itself seems to be flat.

The unit feels secure. In fact, I figured I would take it off and re-seat it just to be sure it is on well and, for the life of me, I cant get the damn thing off. I figured I just pull the bottom away from the wall and then lift up. But nothing.

My guess is that it is because I didnt hit studs under the three tabs that it hangs from and maybe the left one is pulling out just a but that it is ok because I do have six screws that did hit studs. I used toggle bolts like these (http://ecx.images-amazon.com/images/...ML._SY355_.jpg) and of the six I put in only ONE secured properly. On the other five, the screw didnt find the threaded part of the toggle I assume. But, overall, I do have 6 good screws into studs, the one threaded toggle, and two regular-old spring toggles securely attached. So I know the plate is secure.

Any thoughts on if you would think it is on secure. Did you ever notice a gap on yours or any other system? It's been up for about two or three days and hasnt fallen... yet.
 

Last edited by rmathome; 06-07-15 at 07:58 PM.
  #30  
Old 06-08-15, 01:18 AM
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Like I mentioned in your other thread....the only important mounting locations are the ones at the three hanging points. All of the unit is supported at those three cleats.
 
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Old 06-08-15, 06:33 AM
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In the image below, it shows where I put my screws. The green circles are screws that went into a stud. The red circle are toggles, but the toggles really stunk. Only one of them got socked up real tight--one down on the lower right.

So, on the left and center cleats, I hit a stud about 2 inches to the right of the hole in the cleat. I put the toggles in the cleat holes but again, they stunk.

I dont see how the plate can be pulled out, though. I mean, the stud is only two inches away and the unit itself, that hangs on the cleat, is rigid. So I cant see how it could pull on the left without pulling in the center and right.
Name:  hang.jpg
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Last edited by rmathome; 06-08-15 at 08:14 AM.
  #32  
Old 06-08-15, 12:58 PM
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The wall is probably not as flat as you think it is
 
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Old 06-08-15, 04:23 PM
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Just checked with a 4 foot level and it sits flush across it right below the unit.

But, I guess your thinking, based on my explanation, is that it is fine?
 
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Old 06-11-15, 07:21 PM
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Shouldnt I be able to remove the unit fairly easily just by pulling out the bottom and then lifting upwards?

It doesnt seem to work--like it is really on there tight. Am I doing it wrong?
 
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