Lennox GCS16-1853-235 - B41 and A8 diagrams with C1 diagram GCS16-2553,-GCS16-2753-470 or GCS16-3003-470 with basic standard thermostat; C1 DIAGRAM WITH B41 and A8 DIAGRAMS Electromechanical Thermostat Connected to GCS16-2553, -2753 or -3003 with 235,000 BTUH Input Heat (Without Economizer); Operation Sequence: C1 and B9 and A8 Sections (electromechanical thermostat wired to GCS16-1853)