Sizing brackets to wall-mount condensing unit

[mattgus]

Hi all,

I have a question. I have been asked to estimate the size (thickness/gauge) and specific material of two L-Brackets that will be used to mount a condensing unit on the side of a building. As I am at work and don't have any of my school/ME books at my disposal I am wondering if someone could give me a hand for the time being.

For simplicity's sake, assume the unit to be mounted is a 400 lb. box that is 90 inches in all directions (LxWxD). At this time, it is assumed that the box (condensing unit) will be mounted using two angle iron L-Brackets (one on each end of the box). I have attached a very crude sketch sent to me for a visual representation.

Obviously the weight of the unit normal to the ground (and L-Bracket) is the main factor, but I am also wondering about the force causing some sort of rotation and the bottom of the brackets, as the bracket is only attached to the wall on the vertical portion of it and, I would assume, the whole thing wants to rotate about the base of that unit at the point it contacts the wall.

As you would expect, we are hoping for zero deflection. At the same time, my friend would like to be as cost-effective as possible and not buy extremely over-sized brackets. I mentioned he may want to add braces that cross the bottom of the brackets or trusses of sorts from the front of the bracket back to the wall.

Can anyone provide any insight on how to size the angle iron?

Thanks.

 

[mattgus]

To clarify a couple of things now that I have a little bit of time:

Because the brackets will be the same and will be installed so that they each support half of the load (located on the far ends of each side) and assuming that the unit's weight is uniformly/evenly distributed, can I treat each bracket as a cantilever beam carrying half of the weight of the unit?

Can anyone tell me if the fact that the vertical portion of the brackets (and the necessary fasteners to hold them up) can be considered a cantilever beam and function using the normal beam equations or will this style of support drastically change outcome?

Also, because the L bracket has a right angle bend in it (or is two welded pieces of material), will this be a significant weak point? I am assuming that the bend/weld should still exhibit the same properties of the rest of the bracket.

Sorry if any of this is unclear.