AskCodeMan

AC flex duct in contact with IC canister light, is it allowed.

Hi Richard,

The Air Diffusion Council installation instructions states, in 4.3 Installation and Usage, "Do not install near hot equipment (e.g. furnaces, boilers, steam pipes, etc.) that is above the recommended flexible duct use temperature."

The following is from the 2004 Florida Building Code, Residential, w/2006 Revisions.
- M1601.6.2 Flexible air ducts and flexible air connectors.
- - Flexible air ducts, both metallic and nonmetallic, shall comply with Sections M1601.6.2.1, M1601.6.2.2, M1601.6.2.5, and M1601.6.2.7. Flexible air connectors, both metallic and nonmetallic, shall comply with Sections M1601.6.2.3 through M1606.6.2.7.
- - - M1601.6.2.1 Flexible air ducts.
- - - - Flexible air ducts, both metallic and nonmetallic, shall be tested in accordance with UL 181. Such ducts shall be listed and labeled as Class 0 or Class 1 flexible air ducts and shall be installed in accordance with Section M1307.
- - - - - M1601.6.2.5 Air temperature.
- - - - - - The design temperature of air to be conveyed in flexible air ducts and flexible air connectors shall be less than 250°F (121°C).

Thus, with the inside of the duct designed for air temperature not-to-exceed 250°F, combined with the Air Diffusion Council limitations "Do not install near hot equipment (e.g. furnaces, boilers, steam pipes, etc.) that is above the recommended flexible duct use temperature.", that would *indicate* that the outer covering should be able to withstand the same 250°F temperature.

That logic seems flawed to me, and I doubt the exterior covering for flexible ducts will meet that temperature, so I will need to contact the Air Diffusion Council and get a statement from them regarding the limitations on the temperature the outer covering is suitable to withstand.

I will post the response I get back here.

One thing I thought of when I sent the Air Diffusion Council an e-mail was that if the duct is contacting the recessed light fixture housing "by laying on it", then that could be addressed by the fact that the recessed light fixture housing is not an approved support for anything else, especially not for duct work.

Codeman

Hi Richard,

This is the response I got back from the Air Diffusion Council and based on it, resting the duct against the side of an IC rated recessed light fixture *MAY* be acceptable. Note, though, that in my previous response I brought up the issue about using the recessed light fixture (of any type) for support would not be allowed, so the duct *laying on* the recessed light fixture would be a problem.

The exterior of the flexible duct has been tested to a continuous temperature of 125°F, and should be able to sustain a typical attic temperature of around 140°F as the outer covering "will start to soften around 200°F".

Also, if the recessed light fixture is not an IC rated can, the flexible duct is considered to be combustible material and as such is required to maintain the same 3 inch clearance from the recessed light fixture as all other combustible material.

Hopefully this will help finish filling in the blanks.

Codeman

(response from the Air Diffusion Council is below)
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Hello Jerry,

As a member of the ADC engineering committee, I’ve been asked to address your questions.

Flex duct is considered a combustible material in terms of clearance to heat producing/transferring devices. Any required clearance to a device must be maintained with flex duct as well.

Regarding flex duct temperature capabilities, UL181 has a high temperature test that puts 265°F air on the interior and maintains the exterior at 125°F. Therefore, any listed air duct can pass that test. However, 250° objects are going to be a problem for the vapor barrier of most flexible ducts. I don’t know of any published maximum temperature for the exterior of flex ducts since they are not intended to be close to anything hotter than an attic might climb to in the middle of summer. However, I can tell you that polyethylene will start to soften around 200°F. Any item that could reach or exceed 200°F should of course be avoided. I believe that IC rated fixtures would cut off well below this temperature. However, non-IC rated fixtures likely would cause problems, depending on their design and the bulb chosen. The cautions from the light fixture manufacturer should be heeded.

I hope this helps.

Russ Verbrugge
Senior Product Engineer
Hart & Cooley, Inc.
Grand Rapids, MI 49512
Russ.Verbrugge@hartcool.com
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