I repair those boilers and can assure you I fit them whenever I need a regular boiler. There are presently no serious neither any minor faults with them. We hardly ever attend one, I fixed one since September, whereas I have fixed hundreds of combis.
At the moment we are waiting for Alpha to make another mistake as we are not geting much work from them.
They are about to trial some dry pocket thermisters, to make changing a little easier. I see this as pointless, because the alpha isolation valves are excellent there is a very good drain off, and the present white thermisters are bullet proof. (Asside: repairers if you find yourself changing an Alpha white thermister think again, if it's domestic hot water problems indicating ntc's it is sludge in the plate, likewise if the diagnostics say pump, it's the plate. The white ntc's are completely bulletproof, the other colours need changing for white , though we are no longer instructed to do so as a matter of course, I would).
The last real problem Alpha had, has now been nailed, Back emf from the spark ignition process was taking out the spark generator, I believe Baxi experienced same problem but in their case it took out the pcb, for Heatline it took out the spark gen and Biasi also suffered originally but I understand found the problem sooner. Now that everyone has learned of that issue and more importantly how to cure it, we are all twiddling our thumbs.
Presently Alphas are behaving, plus the CDR range is the least likely to go wrong.
