PREMIX SYSTEMS
control valve
combustion chamber
air
8 osi
"A"
6 osi effective pressure 10 osi effective pressure
+2 osi
-2 osi
pressure drop across nozzle
Manometer
EFFECT OF COMBUSTION CHAMBER PRESSURE OR SUCTION ON BURNER CAPACITY — PREMIX SYSTEM
It is really pressure difference or pressure drop, rather than pressure, that affects flow rate (burner capacity). With 8 osi inlet air and a positive combustion chamber pressure of 2 osi, the pressure drop, or "effective pressure" will be 8 - 2 = 6 osi. The flow will be less. If the chamber has 2 osi suction, the pressure drop will be 8 - (-2) = 10 osi and the mixture pressure will be 5"w.c. The nozzle capacity will be based on 5"w.c. To actually measure pressure drop across the nozzle, measure the pressure at "A" in inches wc and subtract the inches wc of combustion chamber pressure † (or add if suction); base the capacity on this effective mixture pressure. The required gas pressure will be increased by the amount of the positive combustion chamber pressure, or decreased by the amount of the negative combustion chamber pressure.
† See page 9, regarding location of combustion chamber pressure tap.
15
Made with FlippingBook - Online catalogs