Ground mounting mini-split condenser

I am ground mounting the condenser (compressor) of my mini-split system. It's currently mounted on the block wall...the vibration is carried throughout the house making sleeping difficult. Even vibration dampening bobbins didn't solve the problem.

I've welded together a stand but need to prep the area underneath. The stand will sit on 2 2x2 foot patio stones on crushed rock. The rock is on site, I just need to decide how deep to excavate, fill with rock and compact. 6 inches? 8 inches? The condenser weighs 80 pounds, the steel stand probably 45-50 pounds.

Ground is still frozen out from the wall, so it's still a week or so away from breaking ground. The dirt in the spot has been undisturbed for about 30 years, so things have settled as much as they're going to I think.

Hints?

 

We have always Just set them on pre poured concrete slabs .

Level them out sit the condenser good to go here in pa

Why a stand to not have to disconnect recharge etc ?

 

Snow level too. Need to keep the back and front clear.
I decided to dig about 12 inches down, coarse rock first. Now I'm just waiting to compact once the ground dries up. The John Deere 1830 will make a mess around there (bucket loading rock) if it's too wet. Nothing I hate worse than seeing slab mounted things sink or slant...like step sets, propane tanks.

 

Couldn't you just level the ground and get one of those concrete over foam slabs? That's what what we used when I did hvac, or a black plastic base if it was a do it as cheaply as possible job.
There never was much of an issue of them sagging or anything unless the dirt washed out from underneath.
If your house has gutters and is graded decent so you dont have a river running where you want to put the condenser and stand I would think that would be fine and less work that digging and filling with gravel.

I'm also in north Georgia so we didnt have issues with snow and the dirt might be diffrent where you are so it could wash out more or something.

 

Frost heaving is the problem here. You can have up and down movement of a couple of inches over a 12 month period. Stable base for things outside is imperative. My propane tank needs one end lifted and rock filled too.