Woodalls Open Roads Forum: Closing duct runs that run past last vent
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 > Closing duct runs that run past last vent

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Cecilt

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Posted: 10/03/13 12:20pm Link  |  Quote  |  Print  |  Notify Moderator

Our 36' TT only has 4 AC ceiling vents(MBR, Bath, LR and Bunkroom). It has a 15k BTU AC. When I popped off the ceiling vent in MBR and Bunkroom the duct works continues past the vent 3-4'. This seems like a lot of air is being wasted and not being diverted out of the last vent. I assume they do this to keep the noise a little lower in those 2 vents but I like white noise. Any issues with closing off the ducts right past the last vent. I would rather do this than drill into the ceiling and add vents. tks

Old-Biscuit

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Posted: 10/03/13 12:27pm Link  |  Quote  |  Print  |  Notify Moderator

How is it being wasted as the extended duct is just a dead end run...doesn't go anywhere?


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TucsonJim

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Posted: 10/03/13 12:37pm Link  |  Quote  |  Print  |  Notify Moderator

x2^

Old-Biscuit wrote:

How is it being wasted as the extended duct is just a dead end run...doesn't go anywhere?



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Homer

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Posted: 10/03/13 12:38pm Link  |  Quote  |  Print  |  Notify Moderator

Air like water will escape through the path of the least resistance. So closing off that small section of over run of pipe will not help you. Actually it forms it own dead head at the vent outlet.

Mocoondo

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Posted: 10/03/13 12:42pm Link  |  Quote  |  Print  |  Notify Moderator

Where is the open end going?

Ducted air conditioners are notorious for very uneven airflow throughout the ducts. Some vents will have air pouring out while other vents seem dead. It is possible that the manufacturer kept the far end open to even out the flow so that a huge temperature disparity does not exist throughout the coach.

I'd check with your manufacturer to be sure, but I'm guessing they kept it open in an attempt at making airflow more even.





p220sigman

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Posted: 10/03/13 01:17pm Link  |  Quote  |  Print  |  Notify Moderator

You could always just temporarily block it off with a towel or something crammed in there and see what effect it has before taking steps to close it permanently.

Cecilt

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Posted: 10/03/13 01:36pm Link  |  Quote  |  Print  |  Notify Moderator

p220sigman wrote:

You could always just temporarily block it off with a towel or something crammed in there and see what effect it has before taking steps to close it permanently.


This is what I was going to do actually. Wasted air might not be the right word. What I would assume happens is as air is being forced down the duct it won't just pour out of the last vent on each run but some or maybe alot of air will contine to head down the duct where it will just dead end. My non-engineering brain tells me logically that if the duct stops at the vent that all the air that hits the blockage will be forced out of the vent and hence much more air into the MBR and bunkroom.

Mocoondo

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Posted: 10/03/13 02:03pm Link  |  Quote  |  Print  |  Notify Moderator

Cecilt wrote:

My non-engineering brain tells me logically that if the duct stops at the vent that all the air that hits the blockage will be forced out of the vent and hence much more air into the MBR and bunkroom.


This is correct and that might be what the manufacturer was attempting to avoid and the simple solution is to just leave the actual duct open at the end.

Keep in mind that even though the duct is currently open at the end, the duct is in an area that is more or less closed, so the boundaries of the area itself becomes the actual terminus of the duct. The fact that the area is not air tight is what helps "soften" the flow out the vents on the line, giving the owner the perception of steady flow out each of the ducts.

I hope that explanation makes sense.

Cecilt

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Posted: 10/03/13 02:08pm Link  |  Quote  |  Print  |  Notify Moderator

Mocoondo wrote:

Cecilt wrote:

My non-engineering brain tells me logically that if the duct stops at the vent that all the air that hits the blockage will be forced out of the vent and hence much more air into the MBR and bunkroom.


This is correct and that might be what the manufacturer was attempting to avoid and the simple solution is to just leave the actual duct open at the end.



I'm hoping this is what they wanted to avoid myself as I think there needs to be either more vents or more forced air into the existing vents. I will try blocking it off and see if it changes the comfort level. tks for the replies.

therink

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Posted: 10/03/13 06:17pm Link  |  Quote  |  Print  |  Notify Moderator

I closed off the ends of both my ceiling ac and floor heat duct runs and it made a very noticeable improvement in air flow. I used cardboard cut to fit and foil tape to seal and hold in place.


Steve Rinker
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