Hvac Duct Fittings Equivalent Length Chart

This article details the calculation of pressure losses through pipe fittings and some minor equipment using the equivalent length method.

Hvac duct fittings equivalent length chart.

From table a 3 the equivalent round size is 9 4 inches. The photo shows front and back sides of the calculator. This value is the comparison length of this fitting to an equivalent length of straight pipe or duct. A 9 1 hvac systems duct design sheet metal and air conditioning contractors national association smacna 1990 chantilly va.

Equivalent duct sizes for same friction loss from. 12 x 7 flat oval 1000 cfm solution. A 8 2 ashrae duct fitting database program. Each fitting has an effective length that equates its pressure drop to an equivalent amount of straight duct.

Back of calculator has equivalent feet of straight duct for commonly used fittings corrected pressure drop chart and many hvac formulas. A 1 3 1 round duct size and area. When you add up the effective lengths of all the fittings and then add that number to the length of the straight sections in the most restrictive runs in the return and supply ducts you find the total effective length tel. The weakness of the equivalent length method is that.

Pull out slide has recommended duct velocities recommended gauges for sheet metal and much more. For example each elbow used is equivalent to 30 feet of straight pipe or duct. The strength of the equivalent length method is that it is very simple to calculate. One method of duct design relies on calculating the total effective length which is the sum of all the lengths of the straight sections of duct and the equivalent lengths of the fittings.

δh friction or head loss inches water gauge 100 ft of duct. The major loss or friction loss in a circular duct in galvanized steel with turbulent flow can for imperial units be expressed. Ordinary heating ventilating and air conditioning duct systems read air pressures at 0 4 psi or less often much less. Fittings such as elbows tees and valves represent a significant component of the pressure loss in most pipe systems.

Southwark metal mfg s sheet metal pipe ductwork and fittings conform to this system of equivalent lengths as well as conforming to industry national standards for describing residential fittings. Energy vanguard this duct design shows the layout of a duct system including the fittings and duct sizes. For rectangular ducts the equivalent diameter must be calculated. 1 psi equals 27 7 inches of water gauge.

δh 0 109136 q 1 9 d e 5 02 1. A common duct pressure of 0 25 inches water column is equal to 0 25 divided by 27 7 in wc psi 0 009.