Eclipse ThermJet Burners for Preheated Combustion Air - Power ...

Step 2: Control Methodology(continued)In the pages that follow you will find schematics of these controlmethods. The symbols in the schematics are explained in the“Key to System Schematics” (see Appendix).Automatic gas shut-off by burner or shut-off by zoneThe automatic gas shut-off valve can be installed in two operationalmodes:1.2.Automatic gas shut-off by burnerIf the flame monitoring system detects a failure, the gas shut-offvalves close the gas supply to the burner that caused the failure.Automatic gas shut-off by zoneIf the flame monitoring system detects a failure, the gas shutoffvalves close the gas supply to all the burners in the zonethat caused the failure.Note:All ThermJet PCA control schematics on the following pagesreflect a single gas automatic shut-off valve. Each schematicshows both operational modes. Only one is necessary.This may be changed to conform to local safety and/or insurancerequirements (Refer to page 9 of ThermJet InstallationGuide No. 206).Modulating gas & airOn-ratio control or excess air @ low fireA burner system with modulating control gives an input thatis in proportion with the demands of the process. ANY inputbetween high and low fire is possible.1.2.AirThe control valve 1 is in the air line. It can modulate airflow to any position between low and high fire air.GasThe ratio regulator 2 allows the on-ratio amount of gas togo to the burner. Low fire gas is limited by the ratio regulator2. High fire gas is limited by the manual butterfly valve3.Note:The ratio regulator can be biased to give excess air at low fireNote:Do not use an adjustable limiting orifice (ALO) as the highfire gas limiting valve 3. ALO’s require too much pressuredrop for use in a proportional system.Eclipse ThermJet PCA Design Guide No. 206, 3/5/0711