Concrete pad for exterior MEP equipment

[cmrdata]

I need to provide two separate concrete pads to support an exterior chiller and electric substation. The frost depth in this area is between 2'-6" and 3'.

I have seen different ways to do this:

1. Simply a think concrete pad.
2. Concrete pad with some small diameter(6"?)piers drilled 3 foot deep located at several selected location that tied into the slab above.
3. Concrete pad with all four edges thickened/turned down (3' deep).

I suspect Method 1 assumed that the utility connections are flexible enough to accommodate the vertical movement of the supporting pad caused by freeze and thaw?

I appreciate thoughts anyone might have.

Thanks.

 

[jayrod12]

You could do a partial thickened edge (say 24") sitting on a 12" thick layer of non-frost susceptible soil. You would still end up with some vertical movement but I'm sure it would be a manageable amount.You should check with the chiller supplier and see what kind of movement they can tolerate with their connections.