Air Handler Mounting Requirements

[Sam Morris]

I inspected a new house today and noticed the air handler in the crawl space was not mounted to the floor joist, it was sitting off the ground on top of cinder blocks. Would this be acceptable.

[A.D. Miller]

SM:

Installation in the under-floor space can be accomplished on a slab of concrete or by support from the floor joists. If on a slab, 3" above grade. If on supports, 6" above grade.

See: IRC 1305.1.4, et al.

Even if the cinder blocks were allowed, and they are not, they are lying in the wrong direction. The voids must always face vertically for proper support.

[Bruce Ramsey]

A.D. you left out some of the code that may allow the use of cinder blocks, albeit in the correct orientation.

M1305.1.4.1. Ground Clearances. Appliances supported from the ground shall be level and firmly supported on a concrete slab or other approved material extending above the adjoining ground. Appliances suspended from the floor shall have a clearance of not less than 6 inches from the ground.

[Jerry Peck]

A.D. you left out some of the code that may allow the use of cinder blocks, albeit in the correct orientation.

M1305.1.4.1. Ground Clearances. Appliances supported from the ground shall be level and firmly supported on a concrete slab or other approved material extending above the adjoining ground. Appliances suspended from the floor shall have a clearance of not less than 6 inches from the ground.

I doubt the concrete blocks would still be acceptable as the unit would need to be secured to them in some way, their contact point in the correct orientation would be limited to the top of the face shells and webs (which is likely why they were installed sideways), and other reasons the concrete blocks would not likely be acceptable for that use (unless topped with a large flat concrete or wood pad, say a 20" x 2" concrete pad (like a stepping stone) set on top of the concrete block. Of course, the concrete blocks in the proper orientation would sink into the ground (another reason they were likely set as they were) and would then need another large concrete pad underneath the concrete blocks ... :)

[A.D. Miller]

In my service area, where we have some of the most expansive clay soil on Earth, cinder blocks would not be an "approved material", as they would likely move independently of one another, i.e. differentially, and thereby move the unit. The unit might not mind, but the wiring, gas lines, ducts, etc. might. . .:D