Hvac Duct Fittings Equivalent Length Chart

The photo shows front and back sides of the calculator.

Hvac duct fittings equivalent length chart. Equivalent duct sizes for same friction loss from. For example each elbow used is equivalent to 30 feet of straight pipe or duct. 1 psi equals 27 7 inches of water gauge. δh 0 109136 q 1 9 d e 5 02 1.

Use the friction chart at 1000 cfm in 9 4 inch diameter to friction loss is 0 5 in water 100 ft. Q air volume flow cfm cubic feet per minute. D e equivalent duct diameter inches. The weakness of the equivalent length method is that.

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. The strength of the equivalent length method is that it is very simple to calculate. A 1 3 1 round duct size and area. 12 x 7 flat oval 1000 cfm solution.

A 8 2 ashrae duct fitting database program. A common duct pressure of 0 25 inches water column is equal to 0 25 divided by 27 7 in wc psi 0 009. δh friction or head loss inches water gauge 100 ft of duct. A 9 1 hvac systems duct design sheet metal and air conditioning contractors national association smacna 1990 chantilly va.

Fittings such as elbows tees and valves represent a significant component of the pressure loss in most pipe systems. Each fitting has an effective length that equates its pressure drop to an equivalent amount of straight duct. For rectangular ducts the equivalent diameter must be calculated. The major loss or friction loss in a circular duct in galvanized steel with turbulent flow can for imperial units be expressed.

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. This value is the comparison length of this fitting to an equivalent length of straight pipe or duct. From table a 3 the equivalent round size is 9 4 inches. Pull out slide has recommended duct velocities recommended gauges for sheet metal and much more.

Ordinary heating ventilating and air conditioning duct systems read air pressures at 0 4 psi or less often much less. This article details the calculation of pressure losses through pipe fittings and some minor equipment using the equivalent length method.