Acquaintance has problem with a 5 radiator zoned system which takes ages to heat up. The boiler (don't know output) fires up normally and after ~ 20 minutes reaches its setpoint of 65C, over the next few minutes it will creep up to 70C and then cut out, again fairly normal if min boiler output is > heat demand. The problem he says is that it will not re fire when the temperature reaches 60c but may go as low as 45/50C before relighting. Now I don't know if this boiler has a anti cycling function but if it has then I assume the anti cycle time is set in a look up table and just looking at one for a Vaillant (spelling) it would seem that a fairly normal setting would be 20 mins so if one looked at the table for 20 mins and a boiler setpoint of 65 it might seem a boiler off time of ~ 5 or 6 minutes but he then said that after each cycle the boiler seems to stay off for longer and longer and he thinks it then doesn't even reach its 65C set point before again cutting out. Can anyone throw any light on this and if the cycle time is say 6 mins should this time be fixed for each subsequent cycle, also does the 6 min cycle time refer to 6 min off and then 6 min on or should it keep firing until it reaches its cut out temperature of 70C, in this case.