I did see one on one of the other forums but it did not cover all aspects. Simple ones have element and thermostat which you wire in series thermostat to line and element to neutral. With bridge between. Some though have twin elements one for full tank and one for part tank and its so long since I have wired one I can't remember what was entailed. Also there are systems for use with off peak power again I know they exist but not wired one. Sparx is your man he seems to have most experience of the sparks on here. What type are you trying to wire and what is your problem?