replacing flexible duct

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bilgert
Posts: 2
Joined: Thu Feb 25, 2010 9:08 am

Thu Feb 25, 2010 9:26 am

Hi-
I'm a newbie to this site and mobile homes, so thanks for your help. I went to a friend of my mom's trailer and noticed that her trailer was freezing. I asked her how long she had been without heat and she answered "months". Gulp. It's been down to 12 degrees on several nights where she lives. I asked her how much her heating bill was and she said $200 a month Gulpx2

I crawled under the trailer and sure enough, it was probably 80 degrees down there. I noticed that the flexible duct had fallen out of the intake collar from the trailer floor and the duct was ripped to shreds by stray animals. Upon closer inspection of the intake grille, I noticed what a horrible job the installer did. he attached the duct to the collar using metal wires tied to drywall screws which were screwed into the collar. I was horrified. Also, the flexible duct was super thin and uninsulated. I felt so sorry for her. She got ripped off bad.

I was looking for some basic advice as to the type of insulated duct I should buy, the type of collar attachments and what to do to prevent animals from attacking the line (she lives in the countryside, it will be a frequent problem). it is a 12-inch diameter vent line.

As a temporary fix, I reattached the existing line and patched it as best I could. I then used duct tape and zip ties to attach the line back. It looks horrible, but it is a 1000 times better than what she had before. Obviously though, I am looking to perform a more permanent fix. I am a handy guy and have worked on basic home repair, installed a plumbing line or two, but I'm not a big HVAC kind of person. Any help would be greatly appreciated.

Thanks!


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Robert
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Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Thu Feb 25, 2010 8:52 pm

Hi,

The wire is the inner part of the duct and is necessary to keep it from collapsing.

Top 3 choices:

1- All metal duct ran between two 90* elbows. Attach with sheet metal screws and wrap seams with foil back tape, then cover that with mastic duct sealant. Wrap duct with plastic barrier covered insulation.

2- Two 90* ells and stretch flex duct tight between them. Attach flex to ells by attaching 4 screws to ells, one on each side. Don't go all the way in with the screws. Loop the spiral inner wire from flex duct over/under the screw heads, then tighten down, cover with foil tape,pull up insulation and plastic cover, wrap with 3-4 turns of foil tape and then tighten with zip ties.

3- Go back with flex duct all the way, attaching the same as in number 2.



On all 3, about every 3-4 feet, support with web strapping or concrete blocking.

All insulation can be covered with chicken wire to help protect it.

Also, securing the underbelly and skirting helps greatly.

You can also get a collar extension if needed.



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?

bilgert
Posts: 2
Joined: Thu Feb 25, 2010 9:08 am

Fri Feb 26, 2010 11:03 am

Thanks for the help Robert!

Would it be bad if I bought a collar extension and ran the flexible duct on the ground as opposed to suspending it with ties and block? The reason I'm asking this is that the ground under the trailer is sloped and the frame of the trailer is difficult to tie off to.

Thanks again.

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Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Fri Feb 26, 2010 4:15 pm

Hi,

You don't want it on the ground, too easily ripped by rodents and also rotting will occur. Plus it adds to overall length of duct and can cause airflow and temp problems.



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?

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