Minimum feet for installation

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LintSmith

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Minimum feet for installation
« on: November 15, 2010, 03:13:43 PM »
Hello,


I was wandering what the minimum amout of feet the dryer vent run can be for the lint alert to perform correctly?





Thanks,
 Sean
« Last Edit: December 31, 1969, 06:00:00 PM by Guest »
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Re: Minimum feet for installation
« Reply #1 on: November 16, 2010, 10:18:47 AM »
Sean, thanks for the posting.

The LintAlert in theory should work for lengths from 12" to 50 feet, but we have taken calls from one or two installers that indicated the unit would not take a calibration on a duct run that was straight out the back exterior wall.  Basically the very very short run, coupled with a very efficient termination hood and likely using the aluminum flex would likely provide such a low back pressure that the LintAlert thinks the dryer is not on.  The present firmware in the LintAlert is looking for back pressure above .20, and in a very very efficient run, it is possible that the pressure levels would be so low the unit refuses to capture the value.  Future versions of the firmware will likely be set to an even lower number to minimize these false positives. 

Your question focuses on run length, when the termination hood style and the type of flex transition hose factor heavily into the calculation as well.  The style of termination hood can have a tremendous effect on the back pressure levels.  This chart is pretty interesting.  www.dryerbox.com/ratings/efficient.htm

Hope this helps,
« Last Edit: August 01, 2013, 10:41:56 AM by rickharp »
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Re: Minimum feet for installation
« Reply #2 on: November 07, 2011, 03:09:05 PM »
Update:
a new firmware version allows for low pressures in the .11 wci neighborhood versus the earlier versions of .2 inches of water column. 
You see, with pressures this low, which is hardly anything, we didn't want the LintAlert to be able to calibrate if the dryer was actually OFF.  With the tolerances in the sensor, the .11 wci is about as low as we can go.  If you have a system that is providing .12 wci of pressure, it is extremely efficient; about as good as it can get. 

Pressures in the .82 and above range or levels that are of concern, and are most likely caused by an old legacy termination hood, either a wall or roof vent.  In most cases, these were the 4" small gooseneck roof vents or the 20 degree hooded flapper side wall vent. 

Nowadays, there exists vents that are much more efficient and can be retrofitted.  Here are links for a very impressive wall vent and roof termination that just came on the market.

Wall Vent: http://store.dryerbox.com/Premium-Flush-mount-Metal-Dryer-Wall-Vent_p_93.html
Roof Cap: http://store.dryerbox.com/DryerJack--Low-Profile--Scoop-Design_p_109.html

« Last Edit: August 01, 2013, 10:49:45 AM by rickharp »
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JR.VOY

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Re: Minimum feet for installation
« Reply #3 on: October 02, 2017, 05:32:50 AM »
Quote from: rickharp on November 16, 2010, 10:18:47 AM
Sean, thanks for the posting.

The LintAlert in theory should work for lengths from 12" to 50 feet, but we have taken calls from one or two installers that indicated the unit would not take a calibration on a duct run that was straight out the back exterior wall.  Basically the very very short run, coupled with a very efficient termination hood and likely using the aluminum flex would likely provide such a low back pressure that the LintAlert thinks the dryer is not on.  The present firmware in the LintAlert is looking for back pressure above .20, and in a very very efficient run, it is possible that the pressure levels would be so low the unit refuses to capture the value.  Future versions of the firmware will likely be set to an even lower number to minimize these false positives. 

Your question focuses on run length, when the termination hood style and the type of flex transition hose factor heavily into the calculation as well.  The style of termination hood can have a tremendous effect on the back pressure levels.  This chart is pretty interesting.  www.dryerbox.com/ratings/efficient.htm

Hope this helps,
It is very good information.
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