Why does the John Wood tankless water heater from the 510 series not produce hot water, and display the error code 111 on the controller?
The ignition failure followed by the error code 111 is one of the frequent reasons why tankless water heater from John Wood's series 510 does not produce hot water. The error code 111 is shown on the control panel's display or temperature controller.
The unit will try to light the gas burner three times, and if it fails, it will turn it off. Here is the procedure that has to be taken to fix the water heater, remove the error code, and resume the heating operation.
Check if the hi-limit switch has tripped. The hi-limit switch turns the heater off if the temperature of the hot water exiting the heat exchanger exceeds the maximum. Turn the power off to the water heater. Push the white button in, and after you hear the click sound, the switch has been reset. Turn the power back on and try to light the fire. If everything is ok, and the fire is on, investigate the circumstances that force the hi-limit switch to trip.
The next thing you should check is if the gas is supplied correctly with the correct pressure and if the gas line is clear of debris and air.
Check the overheat cutoff fuse (OHCF) (it is in white), it might be broken and needs replacement. It wraps around the heat exchanger. Locate the white clip at the end and unplug it. Use the ohm meter to test for continuity. If there is no continuity, you should call the experts.
If the flame comes on for 1-2 seconds before going out, the flame sensor needs cleaning. The manufacturer recommends using the 100 grit sandpaper to clean the flame rod to a bright finish. While cleaning the flame sensor, make sure that its position stays unchanged.
Check the ignitor through the sight glass; it should have a strong blue spark. If it is weak or jumping around, this is not a good sign, and the ignition wires have to be checked for looseness and damages.
Also, check and fix a blockage in the venting system, such as dirt or bird's nest.