My Rheem furnace mod. RGDC-10EC-JS makes a boom sometimes when it starts, it has a spark ignitor.I have replaced the gas valve and ignition module.I have had Rheem certified HVAC techs tell me it is because the burners are dirty but I have cleaned them and inside the furnace where they sit and after a few days I get the the booming again.A camera was run inside and the heat exchanger is good with no cracks. I am at wits end trying to figure this problem out, any suggestions would be greatly appreciated.
I would have them double check the gas pressure before and after the gas valve regulator. If it is dumping too much gas into the combustion chamber when the igniter lights you can get an overpressure that creates a boom noise.