Aquahot/Hydrohot burner failure

[94-Newmar]

Customer unit brought in with a 1 yr old AquaHot unit not working. Was scheduled for yearly maintenance next month. I noticed a lot of carbon/soot almost looked like coal caked around the end of the exhaust pipe. Removed the burner and this is what I found. As you can see it has been having an issue for some time. As of now it appears that the blower/fan motor in the pump assembly itself is failing as it sounded horrible trying to run - like squeaky bearings and the RPM fluctuated wildly. Once I disassemble the pump today and can check fuel pressure and motor/fan speed I'll know more. But for now it appears that it was unable to create enough fuel spray pressure and/or the slower rpm from a bad bearing is not allowing it to draft properly causing an improper burn in the combustion chamber. Part of the air swirler, which is aluminum and fits into the combustion chamber just ahead of the burner assembly has melted in part and was laying in the combustion chamber like a pile of molten magma. The ignition wires jacketing are burnt completely through to the copper core. Amazingly the flame sensor was still intact and it still continued to try to run. The entire exhaust system needs removed from the coach and cleaned thoroughly as well.

Fun fun.....

[MandG-Fun]

Holy smokes (literally)... you're right, amazing that the flame sensor was able to sense anything. And I though my combustion chamber was sooty when I do my annual maintenance.

Owners of AH/HH systems should realize that it is quite simple to do the basic maintenance on the unit or at a bare minimum know how to take off the burner unit to inspect the combustion chamber. In less than 30 minutes you can easily change the burner nozzle, check the electrode gap and clean the combustion chamber and all you need if one screwdriver and two wrenches.

I see a fair number of people posting and complaining about their AH/HH but I'm guessing that these folks also just expect the unit to run forever with no maintenance, just like the owner of this coach.

[94-Newmar]

I just wanted to update this thread as I forgot to after the rebuild...

I got the unit rebuilt and all else is well. I ended up basically rebuilding the entire burner with a new flame swirler, electrodes and wires, fuel nozzle, photo disc, flame sensor, bearing kit in the blower assembly, new blower/pump motor. Fuel pressure checked ok at 145psi. Removed the inner combustion chamber and was amazed at the layers of caked soot. It took over 2 hrs to completely brush and clean the soot. Removed the exhaust pipe and cleaned it end to end.

On this particular coach the AquaHot exhaust runs up and over the rear axle and out the back. This created some low points that collected water condensation and some hard packed soot in those low spots. After cleaning I drilled a few 1/8" holes in both bends that should help prevent further collection of concentrated water/soot.

["007"]

Maybe that's why Newmar runs the exhaust out the side of coach straight though not over axel, not the best installation so Dutch Star Don did some modifications to make it better.