What should the NTC1 temperature be set at on a Vokera Eclipse ESS boiler?

I am still having problems with the boiler not switiching off but have noticed that whilst it is in code 6 mode the temperature is 88oC and I am sure this is too high. The NTC1 has been set at 75oC but should I turn this down? There is a code 5 (low fan speed) displayed when the system gets going and I have read that this indicates a high NTC1/2 temperature. All very confusing and far too complicated! An electrician has tried to find out what the problem is but neither of us can find an answer.