Hi, I believe Ross and I have exactly the same problem. THe sequence of events are as follows.
1. I switch to Central heating and hotwater in combination after about thirty minutes it locks out. Sometimes it locks out earlier when i turn on the hotwater tap.
But sometimes there is no hot water at all for about 15 minutes.
Or there is hotwater for about 20 secs then the taps run cold
2. I Switch to hotwater only, the green light flashes but there is no hot water
I have a sabra 28He (Vokera with adiffernt badge). I have now been told that it could be either the thermistor which needs replacing o the venturi(whatever that is)
The pressure is fine.
Any Comments will be apppreciated.
ED
December 2008