My Intergas HRE40SB boiler anti cycle parameter P is set to 10mins, the default is 5mins.

Iím wondering what the optimum setting, from an efficiency point of view, is for Evohome OpenTherm when at low load?

At lowish loads the boiler heats (5) until the requested flow temperature+5C, ventilates (3), shuts down (1) for the anti-cycle time (10 mins). The flow temp can drop 20C or more in this time. Thatís why I am wondering whether 10min is too long.

At even lower loads. Evohome deploys a low load control algorithm (on/off), Evohome can interrupt the anti-cycle by requesting 10C flow temperature (off). Boiler switches to Pump Overrun (0) until a new temperature request (on). The boiler may then repeat the cycle.

So in this mode the boiler can ignite/ventilate more than once in a 10min interval.