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Old 04-29-2019, 06:12 AM   #1
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Are the AC Vents capped at the end of the run?

Yes, it's me again...Sorry for bugging the living daylight out of you.

It has long been the practice in the RV industry to run the AC duct above the ceiling, but not cap or close the end of the ducts at the ends. Which means that once the conditioned air reaches the end of the vent duct or tube it simply blows out the end and flows into the empty cavity of the end caps of the RV.

Now years ago the story would have been, "yes the conditioned air does dump into the area behind the forward overhead in a motorhome to provide cooling for the electronics ie: TV, stereo, sound system and such"

I have found that over the years if I remove the vent at the far end of each run of duct work and just at this vent location seal the duct thus blocking the air to run free and dump into the ceiling it would create improved cooling in the cabin of the RV.

The Berkshire motorhome that we looked at on Saturday, which was a pleasant Texas Spring day I would guess in the low to mid 80s seemed to struggle in dropping down the interior temperature with both units set a 55 degrees. It just didn't feel cold enough to make me comfortable facing triple digit heat numbers with the two ac units on board.

So, anyway, back to the original question. Does anyone know if the a/c duct work is closed or capped at the ends of the duct run?

Thank you,
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Old 04-29-2019, 06:24 AM   #2
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Not sure on that question. Will say that it is common for the divider in the duct under the AC units to move and or tape fall off an allow cool air directly back into the return duct. Thus, poor cooling of space.
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Old 04-29-2019, 08:10 AM   #3
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Not sure on that question. Will say that it is common for the divider in the duct under the AC units to move and or tape fall off an allow cool air directly back into the return duct. Thus, poor cooling of space.
Interesting thought. How would you check this on these newer vented/ducked units where the return air vents are placed in the ceiling in different areas of the motorhome? I don't recall even seeing a a/c tell/tell sign of mounted location in the ceiling...if that makes any sense.
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Old 04-29-2019, 08:54 AM   #4
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Originally Posted by jonrjen View Post
Interesting thought. How would you check this on these newer vented/ducked units where the return air vents are placed in the ceiling in different areas of the motorhome? I don't recall even seeing a a/c tell/tell sign of mounted location in the ceiling...if that makes any sense.
What's a "vented/ducted" unit? There are A/C ducts (registers) placed throughout the ceiling for a ducted installation but there is only one return and that's at the air conditioner unit intake filter in the ceiling.
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Old 04-29-2019, 08:58 AM   #5
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What's a "vented/ducted" unit? There are A/C ducts (registers) placed throughout the ceiling for a ducted installation but there is only one return and that's at the air conditioner unit intake filter in the ceiling.
On some newer units you can't seen the A/C unit on the inside.
It had ducts/grills in the ceiling (usually in the corners) that return the air to the A/C unit just like in a residential home.

The idea was to make the A/C system "whisper quiet."

Many higher end coaches and 5th wheels are this way now.
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Old 04-29-2019, 09:04 AM   #6
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So, anyway, back to the original question. Does anyone know if the a/c duct work is closed or capped at the ends of the duct run?
Unfortunately the answer is, it depends. We've seen some units where the duct is sealed well on the ends, some where they attempted to seal them but left part of them open, and some where there was no attempt to seal them at all.

In reality, they should all be sealed completely at the terminal ends.
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Old 04-29-2019, 09:12 AM   #7
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Down side of the new design is that the return air is run through the cavity above the ceiling, below the roof which allows the return air to rise in temperature due to heat transfer from the heat of the roof.

With ac units designed to only lower the intake air by approx. 15-20 degrees the ac units may be quieter, but less efficient in the cooling dept.

With the older style ac units where the air return was mounted directly under the ac unit there was no long run of return ducting allowing for heating of the return air going back to the system. Yes, it is louder, but seems to produce better cooling with the old systems.

Don't even get me started on the basement air systems.
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Old 04-29-2019, 10:16 AM   #8
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Originally Posted by jonrjen View Post
Down side of the new design is that the return air is run through the cavity above the ceiling, below the roof which allows the return air to rise in temperature due to heat transfer from the heat of the roof.

With ac units designed to only lower the intake air by approx. 15-20 degrees the ac units may be quieter, but less efficient in the cooling dept.

With the older style ac units where the air return was mounted directly under the ac unit there was no long run of return ducting allowing for heating of the return air going back to the system. Yes, it is louder, but seems to produce better cooling with the old systems.

Don't even get me started on the basement air systems.
So, is the newer type of A/C installation what you're asking about?
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Old 04-29-2019, 10:27 AM   #9
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So, is the newer type of A/C installation what you're asking about?
Yes, the new design is what I am asking about.
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Old 04-29-2019, 10:30 AM   #10
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Yes, the new design is what I am asking about.
Duh, I missed that in the header.
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