Question about Bosch AquaStar Indoor Natural Gas Tankless Water Heater with Vent Hood #125
The flame is sensed by a small metal rod that is immersed in the flame. When you look at the flame inspection window on the lower right of the combustion chamber, then just inside the window you should see 3 rods, and following them down below, then are connected to 3 yellow wires.The right most rod is the flame sensor. It detects the flame when the 118 volt sine wave is rectified by the flame. No flame, 118 volt P-P, flame; flame ignited, half wave only.
EA & EC codes are basically the same, the flame is not detected. EA indicated that during the initial ignition stage there were several errors, while EC tells us that the flame was undetected after the start-up had happen. This is intended to detect that the flame is not burning, and as a safety, shut off the gas supply. If you watch the right hand rod, the flame detector as the startup occurs, and on into the operational period, if you get that far, you may observe that the flame doesn't extinguish, but rather jumps above the detector rod, which also causes the safety to loose the flame retification signal, and shut down. If you vent is clear, you have tested your gas pressure according to the manuel, and the flame does ignite at all, then you likely have the wrong combustion and your CO2 will not be the value for the fuel you are using. You will need to get an expensive device called a Combustion Analyzer to be able to set the correct CO2 levels out the flue. You may be better advised to obtain the services of a pro who has this analyzer and experience using it. Most combustion analyzers need frequent maintenance to replace the O2 sensor inside to have the device read properly.
When you remove the outer cover to service and adjust the system, you should see 2 yellow dabs of sealer that cover the 2 adjustment setting screw heads. The final determination of the correct combustion must be made with the cover in place and tightened. To make that much easier, take a careful measurement from a near by wall, and floor to the center of the 2 adjustment ports with their covers opened. Reinstall the outside cover and mark these 2 points from the previous measurements, and drill a 1/2" hole at each place to allow the tool to fit into the adjustment screws while the cover is mounted. (remove the cover while you drill it!) Follow the manual for setting the P1 & P2 to the correct CO2 level. These adjustments are sensitive and take time to settle after a small tweak - go slow!
Posted on Jun 06, 2012
This is also known as a flame rectification sensor. It basically is what the computer board uses to detect if the pilot flame is lit. When it makes an attempt to fire is there any evidence of flame ignition? This error does not mean that the sensor is bad for sure. The error could be caused because the water heater is only making three attempts to fire and then shutting down. These water heaters are very complex and have many sensors,valves, ect that are all controlled by a computer board. Some of the basic things to check for are... Make sure that you have plenty of gas pressure. These units have a built-in pressure switch and will have issues if they are starved of gas. Most of these tankless water heaters are up to 400,000 btus and a half inch gas line or undersized connector won't work well. You can also check and make sure there is no pipe dope are debris stuck in the screen inside the gas line where it enters unit. Inspect the pilot assembly for debris or obstructions and try to blow out with compressed air. Also look for any loose electrical connectors on the board or to the sensors...one may have come loose.
Posted on Sep 07, 2009
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Posted on Jan 02, 2017
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