Nozzle – Mix burners:
When used with nozzle-mix burners, the vent of a 1218 regulator is cross-connected to the main air line down stream of the control valve. Regulator outlet pressures then equal air impulse pressures, and gas flow remains proportional to air flow at all firing rates.
When a dual-fuel burners atomizing air is left on during gas operation, the 1218 regulator can be set to compensate for the extra air (over the controlledmain air) by adjusting the spring for up to OSI “leak” with no impulse pressure.
With its vent open to atmosphere, a 1218 regulator can be used as an atmospheric, regulator (zero governor) to supply gas toanaspiratormixer feeding premix burners.
If burners nozzles are sealed-in and furnace pressure is other than atmospheric, regulator vent must be connected to combustion chamber. Controlled “Zero” gas pressure then will match furnace pressure, this is necessary to maintain the same air/gas ratioat all firing rates. (See instruction 1218) A separate regulator for eachmixer is preferred to avoid interference or interaction.