Water pressure keeps dropping to 0 on gauge vitodens100-w ?

Restore pressure and watch pressure gauge while c/heating is on to see if pressure rises to 3bar or more, if it does log on to youtube [how to re-pressurise an expansion vessel ] if it is gradually losing pressure you have a leak,if there is no obvious leak check discharge pipe outside usually at the back of boiler water will discharge outside if expansion valve is faulty or pressure has reached 3bar or more

toptrish
December 2013