Air/gas ratio regulator OAR series

Selas Oil-Air Ratio Regulators (Product No. 5301) are used to proportion fuel flows to modulating oil burners. Combustion air flows produce a proportional pressure signal that is applied to the regulator to set the outlet oil pressure. On initial adjustment the desired oil flow rate is set to match the burner air capacities. The regulator holds this oil to air ratio at all firing rates. Pressure balancing of the oil control system eliminates complicated valve linkages on these burners. Heat input turndown over a 10 to 1 range is achieved by varying the position of the combustion air control valve. This simple single valve control is readily interlocked with control motors to process temperature, pressure or other functions to provide precisely the heat required at any time. Oil-Air Ratio Regulators have a unique balanced valve design for inlet oil pressure in the 40 psig to 100 psig range. A constant oil pressure is required at the OAR inlet. Operation The OAR regulator will efficiently control #1, #2, and #4 grades of oil. A load line from the combustion air supply at least 10 pipe diameters downstream of the combustion air controlling valve is connected to the control air impulse line. A 1/4” load line is sufficient. A reducing regulator should be installed upstream of the OAR regulator to provide constant oil pressure. A variation of 5 psig at the inlet can cause a 2% error in flow control. Air pressure from the load line forces the main diaphragm upwards opening the oil outlet valve. The oil pressure in the outlet chamber applies pressure on the oil piston which opposes movement of the main diaphragm and tends to close the oil outlet valve.