PREMIX SYSTEMS
OPERATION OF AN ASPIRATOR MIXER
The nominal pressure ratios for a North American premix system are 8 osi air pressure, 8 osi suction, 4"w.c. mixture pressure. These are approximate. There is a wide range of control from slightly lean to rich (depending on the burner) with gas of 800 Btu/ft3 or more. If these pressures (or the same ratio of pressures) do not exist, check for excessive restrictions in the mixture line or burner.
Control valve
Burner may be sealed-in or open type.
Air
8 osi
4"w.c.
Rod is used to size mixer to match nozzle(s)
Gas
8 osi with gas shut off
1st: Set high fire ratio using built-in limiting orifice.
Zero gas pressure
2nd: Set low fire ratio, see page 21.
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