1) Work out which Atag boiler you have. (Its yours, you should be able to find out)
2) Find the manual. If you have it or locate online. SHould be easy.
3) Read the manual. I believe E02 means flame not formed but please check in the manual.
4) Search for your specific boiler and the error code on line That may give some self-help info
5) Get a GAs Safe engineer to service it.
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October 2015