Noisy Water Heater Redux

My wife and I enjoyed your classes at the RVSEF Conference in Bowling Green a few years ago. Now I have a question regarding the Atwood water heater in my 2013 Jayco Eagle Premier. The heater is model GC10A-4E. When running on propane with the outside access door open the heater appears to operate normally and burns quietly with a light blue flame. When I close the access door, the heater seems to adopt a dual personality. Part of the time it is quiet just as with the door open. But part of the time it burns with a roar, kind of reminding me of a mini jet plane. It switches back and forth between quiet and loud several times a minute. I can interrupt the loud periods by opening the access door. I have disassembled the burner and checked for blockages, but everything is open and clean.

I have found two ways to make it noisy more frequently, but none to eliminate the noise entirely. I set the air to fuel ratio per Atwood's instructions, closing the air shutter until the flame begins to show areas of yellow, and then opening it slightly until the flame is all blue. I can make it noisy more frequently by increasing the air to fuel ratio via opening the slots in the air shutter. The second way to make it noisy is to cover the ventilation cutout on the access door with window screen to keep out insects. If I put standard aluminum window screen over the cutout it roars about 90% of the time. This suggests to me that it needs a larger cutout, but if that were the case then all owners of this model would have a noise problem. How do you suggest I troubleshoot this problem? Jack S.

Jack, you’ve already solved one part of the problem with a noisy water heater; that of the proper air/fuel mixture adjustment. The other tricky factor is the alignment of all the pieces from the main burner orifice, through the mixing tube and to the ignition probes at the flame spreader at the mouth of the burner. The mixing tube must be properly in line with the face of the orifice fitting; a straight line that is determined by the angle of the gas control valve and the brass orifice fitting attached to it. Likewise, the orifice opening must be “centered” in the open end of the mixing tube. Picture a clock face. The orifice itself must be positioned at the very center of the clock where the hour and minute hands attach. If it’s off-centered or if the mixing tube is not aligned with the angle of the orifice fitting, as gas enters and draws in fresh air, the combination of the mixture results in an uneven mixture of gas and air and a turbulence is created instead of an even, steady flow of mixed air and fuel. This fluctuating turbulence is the source of the soft/loud combustion taking place. Check out this video.

I believe once you check these additional items and reposition the primary air opening for optimum performance you’ll be able to eliminate the problem. Here’s a short video explanation regarding the adjustment of the air shutter. 

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