The Eberspacher Hydronic D5WS can have the heater lockout cleared by the handheld diagnostic unit 221545890000. To connect the basic diagnostic test unit to the Hydronic D5WS you will also require the adapter 221000316300.
Fault code 50 is a lockout due to too many failed starts of the heater. Please check there are not any other fault codes that could indicate why the heater has failed to start in the first place.
For the Eberspacher Hydronic D5WS Fault Error Codes, please see link -
https://www.butlertechnik.com/downloads/cms/7491/eberspacher-espar-d5ws-fault-codes-errors-manual.pdf
For All Eberspacher Hydronic D5WS Technical PDF Manuals, please see link -
https://www.butlertechnik.com/technical-library/hydronic-d5ws
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