I have a 4" flex HVAC duct near my tent.
I want to tie into it with a 4" inline fan and send it to my tent.
If I put a 4" damper at the tent port, will the damper be tight enough to prevent HVAC air from entering the tent passively when the inline fan is not operating?
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I would expect you will get some air pushed past the damper. In my experience they all leak somewhat.
Cheers
G
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Also wondering if my 8" AC Infinity exhaust fan will pull open the damper when it turns on.
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Happy Sunday OG family !!! I think the question has some variables to it. The 8” fan will definitely open a damper. However there is a few ways to remove air or circulation ect to work in conjunction and not complete against one another especially if your adding AC. Any way you can get a pic of your situation or something similar we can make sure you’re on the right track. Cheers !!!
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if you tie in there the furnace fan will beat out the 4" fan and steal air out of the tent the furnace fan is 10 times bigger than the 4" it is a matter of cfm’s
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Excellent diagram. 2 things to review. That’s a powerful extraction fan and would need to be set on a controller and or variable speed controller. That’s perfect as we always suggest oversized fans and adjust them down to meet our requirements. The second thing to review will be how much suction will be created by your ac duct line. To be clear the 4” flex line is it an AC feed duct to a vent in the house or a small extraction vent line for humidity extraction in a bathroom ?
#1. Dampers are more effective installed closer to the source. Instead of at the tent it would go at the tee fitting you want to install.
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@Hemlock has that right, put the damper just after your takeoff from the supply trunk. The 8" fan shouldn’t pull the damper open if you have everything pretty tight.
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#2 dampers aren’t sealed 100% so there will be a certain amount of leak by.
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Excellent information on the dampers. I’m not fairly convinced that’s a 4” AC duct line to a vent. Looks an awful lot like a 4 inch humidity duct for the bathroom. Definitely want to double check that.
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If unsure about it being a HVAC duct take some more pics of that area and follow it to the furnace/air handler.
Long story short you are likely better conditioning the basement air as the “lung” and using the tent as designed.
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Yes the extraction fan has 10 variable speeds and is operated by the controller. I will also have the controller operate the 4" inline fan.
The 4" flex line is the result of a bathroom remodel where the old vent had to be moved. The original feed comes from a 6" steel duct where it is reduced to 4" and connected via the flex line to the new location.
I’m planning to add a 4" T as shown below (and I can put the damper at the T instead of at the tent):
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You are then looking at a damper that is not a standard adjustable, more a barometric. The problem you will run into is the furnace/air handler will blow it open, the same as the inline fan will pull it open.
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So to achieve what you are going for you will need a power damper that is controlled open or closed. That adds money and complexity.
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This is a little bit different than most situations. I think the concern is, what will the damper do just past the reducer at the T when your in line 4” fan is not on. Will that damper still be pushed open by the air going to the bathroom register. Would it be minimal and not really affect much or will it remain closed as intended. I think this is worth reviewing maybe you can do a test as I can see the cost savings, not running a separate AC unit or ducting if it’s not already in place to the lung room .
I’m also not sure you even need the 4" inline fan. A powered damper on the 4" duct and the 8" inline should do the job. Leaving a spot open on the controller to cycle the damper.
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A quick search brings this up
I assume that controller has a port for 120v plug?
Power dampers are also sealed so no air blowby or backwards gravitation into bathroom.
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Yes! I think this might be the best solution.
The controller could operate the electric damper… then passive HVAC air would enter the tent without the need for the 4" inline fan.
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Yeah even when the HVAC is off the 8" will still do the work pulling the air from the rest of the house. The controller will likely have a demand at times when HVAC is not operating.
This setup should be what you ar looking for.
Heating or cooling
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