Thread: A/C & "Great Foam"

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To keep standing water after heavy rains out of the bottom. In hurricane zones(at least here) it's 4 inches. It used to be that the pads were also required to be minimum 90 pounds, but that disappeared with the adoption of the IRC in 2003.

Does the condensate line have a trap?

Rust, mosquito breeding, potential electrical issues.

There are several types of expanding foam. Some are specifically for interior use only. Others declare suitability for weather exposure. Yes, I do call them out, but usually it is in a manner to recommend regular monitoring of the performance of the product used for weather related failure, rodent damage, shrinkage, failure of any type.

Jeff Eastman"Rust, mosquito breeding, potential electrical issues"

Would you not get the same issues from rain coming in from the top of the A/C and ponding on the inside? Therefore, why bother writing up for repairs that the pad is below grade level?

When water is standing above the level of the pad, it can't drain out. If you get the bottom above the standing water, it drains out to the pad. I have no idea how they came up with three inches (or four).
And it should be above finished grade. So I notify the Client that once the sod is laid the unit will no longer be 3 inches above grade.

I haven't heard of the 3" requirement.
I see no problem with the foam.

Originally Posted by Jeff Eastman

- Why does the A/C pad need to be 3" above grade?

Because the bottom of the units will rust out if water is allowed to collect and stand on/in it.

- Do you guys consider it a defect when great foam is used to seal gaps around penetrations out of the house?

Yes, when not protected from sunlight, it is NOT sunlight resistant, thus it deteriorates. Besides, for rodent proofing the chases, they just dig it out over time. Protect it with a coating of paint (minimum) and a metal screen (rodents), I always recommended a piece of sheet metal be cut to fit and screwed in place.

Originally Posted by Eric Barker

I haven't heard of the 3" requirement.

It must be in the mechanical code. I can't find it in the IRC. I got it from the 1998 TX windstorm code and I seem to remember it from Mfr. installation instructions, but that could be another false memory. There's actually an illustration in the HVAC code check, but no refernce as to what section they got it from. Any help here, HVAC guys?

Thom,

From the IRC.

- M1403.2 Foundations and supports.

Supports and foundations for the outdoor unit of a heat pump shall be raised at least 3 inches (76 mm) above the ground to permit free drainage of defrost water, and shall conform to the manufacturer’s installation instructions.

Here's a good?? use for it.

Originally Posted by Jerry Peck

Thom,

From the IRC.

- M1403.2 Foundations and supports.

Supports and foundations for the outdoor unit of a heat pump shall be raised at least 3 inches (76 mm) above the ground to permit free drainage of defrost water, and shall conform to the manufacturer’s installation instructions.

Like I said, it's right there in the IRC. A blind man could see it!

Anybody see my glasses?

Thom:

We have a driveway paving company around here who think's it's 3" below.

Urethane foams not rated for direct exterior exposure.

3" requirement for surface water run off and a stable platform.

Originally Posted by Eric Barker

Thom:

We have a driveway paving company around here who think's it's 3" below.

"Well, Homer, got that hole dug yet? We got two more to install today."