Originally Posted By: rhjelmeland This post was automatically imported from our archived forum.
I recently performed an inspection which turned up what I perceive as a fire hazard. The dryer vent exhaust line was ~20ft long and suspended in the crawl space over a single floor joist cross braceing. The end result is that the very long dry exhaust line looked like a piece of Christmas Garland. My concern is that the long run plus the two “sags” in the line could trap lint, and in the long run this may result in combustion. In our area the local fire inspector determined that a similar situation resulted in the a fire which destroyed a home that was used as a childs day care.
Some basic research informed me that most dryers can only drive 15ft with 2 elbows without a secondary fan.
Does anyone know of codes/regulations that govern the length and type of material used for dryer vents?
Originally Posted By: aslimack This post was automatically imported from our archived forum.
I believe its 25 ft. maximum, with a 90 degree bend counting as 5 ft. and a 45 degree bend counting as 2 1/2 ft.
Example: 15 ft. with 2 90 degree bends equates to 25 ft. I definitely recommend straight wall metal venting, NO SCREWS. This is even more important with the longer run.
Originally Posted By: rsummers This post was automatically imported from our archived forum.
The rules we live by here in Butte county are if you use 4" pipe its total length can not exceed 15’ after factoring in the elbows. If the vent is more than 15’ you go up to 5" and they enforce no length limit. They also require that they are insulated to prevent condensation.
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
I total agree to the issue of dryer related fires. I had a dryer fire about 10 years ago. Fortunatly I caught it time that it did not do any serious damage. Now, every year I use my air compressor and vacumn to completly remove all lint from the dryer vent and the inside of the dryer (I take the back panel off). Surprizing just how much lint ends up there.
While I don't advise my clients to go to such extreme, I do caution them about dryer fires and venting properly.
Originally Posted By: scieslewicz This post was automatically imported from our archived forum.
Robert,
All good posts above. One thing that I've been making the HVAC guys change a lot lately is the duct tape on dryer vents. It's taken several months but they're all using U.L. rated metal tape now.
On the same lines, another common fire hazard is paper backed insulation batts in the attic right up to the b vents. The IRC in Chapter 24 references an insulation shield. The paper is combustible and should not be in contact with the vent!! If you see it, you may want to recommend a shield or cutting back the insulation.