The Dryer-Ell - Dryer Vent Duct Elbow Comparison
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Length of Run Improvements Delivered by the Dryer-Ell
Dryer Vent Elbow Comparison - Underwriters Laboratories

Venting Elbow Volumetric Air Flowrate Comparison

Dryer Vent Duct Elbow Compared - Six Long Turn Duct Elbows equivalent to One Standard Sectioned Dryer Vent Duct Elbow Underwriters Laboratories completed a 2006 fact finding study that shows a dramatic improvement in air flow when using the new long-turn dryer venting elbow versus a typical sectioned duct elbow.  One of the findings is that it takes six long turn dryer elbows to have the equivalent affect on flowrate as a single sectioned elbow.

Sectioned Dryer Elbow Duct-length Equivalency

Further, the study found the actual affect of sectioned dryer elbows is equivalent to 15 feet of straight pipe.

One Typical Sectioned Dryer Vent Elbow is Actually Equivalent to 15 Feet of Duct Run

Report Link: 2006 UL Fact Finding Report - CLOTHES DRYER VENT DUCT LONG RADIUS 90 ELBOW
Dryer Vent Duct Run Impact - Current Code

Length of Run Penalties under Current Dryer Venting Code

Most code, today, still reflects only a five foot reduction in length-of-run for every ninety degree turn in the duct.  This seeming disparity, however, is somewhat offset by the very short overall run length allowed (most dryer OEMs allow longer).  There are proposals before the ICC to bring both variables closer together.  For now, there is a 5 foot reduction for every typical elbow from an overall 35 feet in allowable length.
  • 504.6.4: 35 feet less 5 feet for each typical 90 degree elbow and 1.5 feet for each 10" radius elbow.*
  • M1502.4: 35 feet less 5 feet for each typical 90 degree elbow and 1.5 feet for each 10" radius elbow.*

  • *  Dryer-Ell Model LT90 Actual Length is 1.5 Feet
  • 504.6.4: 35 feet less 2.5 feet for each typical 45 degree elbow and .75 feet for each 10" radius elbow.**
  • M1502.4: 35 feet less 2.5 feet for each typical 90 degree elbow and .75 feet for each 10" radius elbow.**

  • **  Dryer-Ell Model LT45 Actual Length is .75 Feet

Current Allowable Duct Length Under Dryer Venting Code

Comparison of New Long Turn Dryer Vent Elbow to Standard Sectioned Dryer Vent ElbowDryer Vent Duct Run Length of Sectioned Elbow versus Long Turn Dryer Vent Elbow

Based on accepted ASHRAE methodology for calculating friction loss in ducts and fittings, this new elbow provides key benefits to the builder and tradesmen by removing the reduction consequence found in most building codes.  Section M1502.6 of the 2006 International Residential Code, Section 504.6.4 of the 2009 International Mechanical Code and Section M1502.4 of the 2009 International Residential Code all permit large radius elbows.

Click HERE for Calculations and Engineering Reports.

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