Well I'm not sure what the inside of the g200 looks like, but right now I have the g400 and it has air injection tubes that are on both sides of the door just inside and I have had them plug up many times so far this year, especially when we have warmer days. It has plugged off right to the point that no air gets through and the water temp just drops. I had a heck of a time finding something that I could get down the air tubes to clean them out, turned out a urinal power snake finally made its way to break through the cresote to get the air flowing again. But again the problem is everytime it gets warmer again, the boiler is so efficient that it smolders when not calling for heat to raise the water temp, that the tubes plug again. I got so tired of it that I made a deal with my dealer on trading it in for a 10000e. I will be actually changing it out tomorrow.