Foundation Mount Central AC Unit

[flumiani]

I just got a central air unit installed in a new construction house. The unit is mounted on the foundation wall on steel "L" brackets just below brick level. When the unit is operating outside it doesn't seem very loud but inside I seem to be getting lots of low level vibration (even on the 2nd floor above the outside unit!) I've heard suggestions of rubber spacers between the unit and the brackets, a rubber gasket between the bracket and the foundation, an extention on the bracket to a triangle shape instead of the "L" etc. Is any of this worth trying or do I really need to remount it on the ground?

The only issue with the ground mount is that my soil grading hasn't been done yet so I would need to wait. I also think I would need to go maybe 4 patio stones thick to get to the same height as it is now from where I anticipate the fill level will be. Any problem with that or is making a box filled with crushed stone topped with one patio stone perhaps a better base than stacking patio stones?

[lp13-30]

I have only seen a/c units mounted like yours while visiting in upstate NY. I assume it is for snow, which is not too much of a problem here in south Texas. However, if you are paying for a new house, you are entitled to have it fixed right. Putting the unit on patio blocks, crushed stone or whatever, is not right. Vibration noises inside are not right either. Insist that the builder get the A/C contractor make it to your satisfaction, period.

[SQLit]

Send pictures of the installation. The way you describe this can not possibly be correct. I know of no residential condenser that is designed with clearances that close. Most require a 2 foot minimum clearance.

[Joseph Meehan]

I have a like setup. I find that occasionally vibration has caused the unit to move just enough that it is not really evenly set on the brackets and needs to be moved maybe an inch. When it is solid on the brackets, it is quiet.

[flumiani]

I double checked and it seems that mine is actually bolted to the brackets. I'm assuming that it is centered.

Appreciate the reply.

[flumiani]

I live up North yes, and hadn't really considered snow as the reason for the foundation wall mount. I believe the biggest convenience of the brackets is that you don't have to worry about the backfill settlement around new construction since it is right on the wall. Unfortunately that is causing my vibration issue.

The A/C installation was done with a seperate contractor from my builder. They visited today, insisted the wall installation was done right and that the unit was functioning normally and that the best thing to do would be to get it off the wall and onto the ground (at my further expense of course).

[flumiani]

I don't have access to a camera at the moment unfortunately so I'll explain as best I can... The L brackets have one plane facing downwards attached to the foundation wall and another running parallel to the ground. The unit sits on the backside/end of the L furthest away from the house, likely 2 feet clear of the wall as you mention. It is bolted directly into the brackets and the brackets are bolted right into my concrete foundation wall, right below where the brick line is.

\ [ ] \ (brick) [ A/C ] \ [ unit ] | ___________________ | | | | L bracket | | |

[George E. Cawthon]

First question is, did you check the hoses to make sure they were insulated where they run into the house?

Second, get the damn thing off the wall. When you get the soil graded right, make a form for a concrete base for the unit to set on and use ready mix bags. Depending on weight of the unit, it should be 3" or so bigger than the base and at least 4-6" thick. Shim between the base and unit with redwood or cedar to level if you need extra height or the concrete base shifts. Mine base hasn't moved in 25 years and we have lots of freeze thaw. Then the soil will dampen any vibration and the only parts attached to the house are the hoses and electric wires.