I have an Eternal GU195S that is from 2012. The original plumber installed the whole water system without a PRV and pressure on the house was 160psi. What prompted the call to begin with was loss of hot water. We had gone out and installed a PRV on the system and it helped a little but did not solve the problem. Did a full diagnostic on the water heater and found that it thought it was literally working as it should but was only producing 2 gpm at 130 degrees. Anything past that it couldn't keep up. I did notice it was making some loud popping sounds and racket when in full burn. From what I've seen of the burner design, it looks to vortex in the middle of it's 2 gallon holding tank. I think the tank may have failed but not ruptured and has warped/exploded/imploded due to high pressure and is not allowing even spread of the burner on the exchanger causing any flow above 2 gpm to not heat adequately. My main questions are, should I try and replace that burner and holding tank assembly? And if so, where can i even get the part since they are out of business? Or should I just take a sledge hammer to it and install a Rinnai? I have the owner interested in a Rinnai, but I just think it would be a shame to pull a nearly new unit out if it can be remedied for 500 or less since a new Rinnai install will be 2000 bucks minimum.
I installed dozens of 195's but spent a lot of time making sure they were correctly installed. Therefore I never really developed a good knowledge of repairing them. There are 10 in my neighborhood alone, all still working. I wished there was help on repairing them as they are very good at creating lots of hot water.