Rinnai ByPass Servo Troubleshooting Manual page 13

indication the fins inside the heat exchanger are clogged with debris. If you have heat damage on the
surface of the heat exchanger, replace the heat exchanger.
12. On internal units inspect the plastic tube running from the bottom of the combustion chamber to
the gas valve. If you find moisture in that tube replace gas valve. Also inspect the vent system to see
where the condensate is coming from. It could be a venting issue or leak inside the heat exchange
combustion box area.
13. Ensure the condensate drain trap was used as recommended by Rinnai on the vent terminal
connection at the top of the water heater, non-condensing product. If the condensate drain line is not
connected please install one per Rinnai venting instructions. If a condensate line is in use, inspect the
vent connector on top of water heater to ensure it's not stopped up. If stopped up remove vent pipe
from unit and clean out all debris or build up in the trap or drain lines.
14. Inspect fan blower wheel for debris and/or insects. Important; turn off power to unit before
unplugging fan motor or plugging it back up. Failure to do so can short out fan motor. If insects or debris
are found in the fan housing or burner assembly, inspect the entire intake air chamber to include the
vent system and air box chamber.
15. Check to ensure all two stages regulators are installed at least six foot away from appliance. Ensure
when appliance shuts off the pressure from the two stage regulator doesn't exceed the maximum inlet
pressure for the appliance. To check this, connect your manometer up to the test port on the bottom of
the water heater. The inlet pressures should never exceed 10 inches water column for natural gas or
13.5 inches on propane. If it does the regulator may be defective.
16. Inspect all wiring harnesses throughout unit for water or moisture in electrical connections. If any
connections appear to be damp or wet dry them out and try to find out what is causing this. This can
cause a short circuit which will lead to code 12.
17. If any MSA or MSB system is in use isolate the unit from that system and see if it operates without
going to a code 12. A short circuit within those systems can cause a code 12.
18. See below for other suggestions:
a. Remove the four burners located under the flame rod and move them over to the high fire side of the
burner tray. Move the four burners from the high fire side over under the flame rod. Sometimes
condensate or debris can get down in the burners and cause turbulence inside the burner.
b. Condensate, debris or a malfunctioning mechanical component inside the gas valve may be
preventing the valve from opening correctly once in a while. Replace gas valve.
c. Voltage output to gas valve from PC board could be incorrect or intermittent due to a bad component
on PC board, replace PC board.
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