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SERVICING A GAS STREAM B .023" - .027" Beckett Burner WARNING The length of Dimension "A" determines the angle of Gas Stream "B". DENT OR BURR DISCONNECT ALL GAS AND ELECTRICAL POWER SUPPLY. In checking main burners, look for signs of rust, oversized and undersized carry over ports restricted with foreign material, etc, refer to previous drawing. Burner cross-over slots must not be altered in size. S-306 CHECKING ORIFICES A predetermined fixed gas orifice is used in all of these furnaces. That is an orifice which has a fixed bore and position as shown in the following drawing. No resizing should be attempted until all factors are taken into consideration such as inlet and manifold gas pressure, alignment, and positioning, specific gravity and BTU content of the gas being consumed. The only time resizing is required is when a reduction in firing rate is required for an increase in altitude. Orifices should be treated with care in order to prevent damage. They should be removed and installed with a box-end wrench in order to prevent distortion. In no instance should an orifice be peened over and redrilled. This will change the angle or deflection of the vacuum effect or entraining of primary air, which will make it difficult to adjust the flame properly. This same problem can occur if an orifice spud of a different length is substituted. GAS STREAM B A dent or burr will cause a severe deflection of the gas stream. S-307 CHECKING GAS PRESSURE Gas Supply Pressure Measurement CAUTION TO PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE, THE INLET GAS SUPPLY PRESSURE MUST BE AS SPECIFIED ON THE UNIT RATING PLATE WITH ALL OTHER HOUSEHOLD GAS FIRED APPLIANCES OPERATING. Gas inlet and manifold pressures should be checked and adjusted in accordance to the type of fuel being consumed. The line pressure supplied to the gas valve must be within the range specified below. The supply pressure can be measured at the gas valve inlet pressure tap or at a hose fitting installed in the gas piping drip leg. The supply pressure must be measured with the burners operating. To measure the gas supply pressure, use the following procedure. WARNING WARNING DISCONNECT ALL GAS AND ELECTRICAL POWER SUPPLY. DISCONNECT 1. Check orifice visually for distortion and/or burrs. 2. Check orifice size with orifice sizing drills. 3. If resizing is required, a new orifice of the same physical size and angle with proper drill size opening should be installed. ELECTRICAL POWER AND SHUT OFF GAS SUPPLY. 1. After turning off gas to furnace at the manual gas shutoff valve external to the furnace, remove burner compartment door to gain access to the gas valve. 2. Connect a calibrated water manometer (or appropriate gas pressure gauge) at either the gas valve inlet pressure tap or the gas piping drip leg as shown in the following figures. Refer to Measuring Gas Pressure: Single Stage Valves figure for single stage valve inlet pressure tap connections. Refer to Measuring Gas Pressure: Two-Stage Valves figure for two-stage gas valve inlet pressure tap connections. 53