Hvac Duct Fittings Equivalent Length Chart
Pull out slide has recommended duct velocities recommended gauges for sheet metal and much more.
Hvac duct fittings equivalent length chart. A 8 2 ashrae duct fitting database program. Equivalent duct sizes for same friction loss from. A common duct pressure of 0 25 inches water column is equal to 0 25 divided by 27 7 in wc psi 0 009. The weakness of the equivalent length method is that.
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. A 9 1 hvac systems duct design sheet metal and air conditioning contractors national association smacna 1990 chantilly va. Use the friction chart at 1000 cfm in 9 4 inch diameter to friction loss is 0 5 in water 100 ft.
This article details the calculation of pressure losses through pipe fittings and some minor equipment using the equivalent length method. From table a 3 the equivalent round size is 9 4 inches. 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. Fittings such as elbows tees and valves represent a significant component of the pressure loss in most pipe systems.
12 x 7 flat oval 1000 cfm solution. Ordinary heating ventilating and air conditioning duct systems read air pressures at 0 4 psi or less often much less. For rectangular ducts the equivalent diameter must be calculated. δh 0 109136 q 1 9 d e 5 02 1.
Q air volume flow cfm cubic feet per minute. A 1 3 1 round duct size and area. Each fitting has an effective length that equates its pressure drop to an equivalent amount of straight duct. δh friction or head loss inches water gauge 100 ft of duct.
Energy vanguard this duct design shows the layout of a duct system including the fittings and duct sizes. D e equivalent duct diameter inches. 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. 1 psi equals 27 7 inches of water gauge.
Back of calculator has equivalent feet of straight duct for commonly used fittings corrected pressure drop chart and many hvac formulas. The strength of the equivalent length method is that it is very simple to calculate.