Did a preventative maintenance on a boiler. During the maintenance I did combustion test the ppm was 34 and the o2 was 9. Checked the expansion tank. Made sure that the return was coming back hot. Did a amp check on the circulator and that was .61 and rated for 0.74. Took out all the burners cleaned them out and inspected the pilot assembly. System is operating properly at this time. M#CGa-4 PIDN s#CP7469916