The past few days I have been troubleshooting a Bradford White direct vent water heater. The problem started when an owner of a hair salon called in a panic about their water heater not working properly.
When I arrived the owner had re-lit and the heater was operating normally. Bradford White heaters of this age, approximately 8 years old, have been know for gas valve issues. My first thoughts were of a gas valve or thermopile however the LED indicator was not displaying anything except normal operation. I had been told by the owner that the LED had indicated low thermopile output the day before.
I checked the thermopile output and determined the 415 milivolts was in fact normal for this heater. Historically the gas valve pilot assembly replacement was needed to correct the intermittent performance of the heater. Unfortunately the part was unavailable locally and would take 4 days to order. Because the heater was never in a non working condition while I was there it was difficult to determine with 100% certainty the problem. The other hypothesis was that the heater could be starving for oxygen due to problem with exhaust and inlet air. Direct vent heaters get their combustion air from outside through a concentric vent.
Several days went by, several plumbers looked the heater and proposed multiple solutions including replacement. After multiple trips out, I determined the combustion air had some impact on performance. At one point we kept the combustion chamber door off to view the flame during operation. For some reason this improved the reliability of the heater. It worked well for several days.
Just prior to replacement of the entire heater to a tankless solution we inspected the flame quality as a last resort to determine the Air fuel mixture. If the burner flame is yellow this indicates a low oxygen situation which would point to problem in the inlet air. If the flame is blue this would indicate the proper air fuel mixture.
I used my camera to evaluate the burner and was surprised to see a blue burner flame with a yellow pilot flame that was misdirected in around the pilot. This was a smoking gun. Clearly this was not proper operation and could easily be repaired.
We installed a new pilot assembly $40 part and corrected the flame quality. The heater appears to be working flawlessly! Because the owners we ready to replace the heater to correct the problem we literally saved them thousands of dollars.