PREMIX SYSTEMS
control valve
optional cross-connected impluse line if higher mixture pressure is required*
air
5 D
3 D
flame
8 osi
4 1/2 "w.c.
4"w.c.
gas
Limiting Orifice
gas pressure = zero (if no impulse) or equal to air impulse if used
required gas pressure = pressure drop through regulator + safety factor + air impulse (when used)
PREMIX SYSTEM IN USE
As restriction in the mixture line is increased, the mixture pressure will rise and the suction will be reduced. If the restriction is sufficient to cause the suction to be too low to supply enough gas, a smaller capacity mixer and rod (or less outlet restriction) is required. Mixture piping should be sized for a low pressure drop, 0.5"w.c. or less. In a typical installation, the regulator would be sized for a minimum 2 osi drop, and a safety factor of 1 osi would be allowed, requiring a gas supply pressure to the regulator inlet of 3 osi (See page 24 for detailed sizing instructions). * If necessary the 7218 Regulator may be cross-connected to the air or mixture line to overcome the effect of high restriction in the mixture line or nozzle.
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