In my experience this sort of problem seems to be worse when the boiler has been completely switched off. Otherwise it apparently learns to reign back more quickly, during the full power run shortly after ignition, in systems where the full output can't be handled by the water flow available.
I don't think it's only the differential in temperature that triggers the S53 code but also the rate at which the flow temperature is increasing. If it goes up alarmingly fast the boiler assumes the worst.
I don't think it's only the differential in temperature that triggers the S53 code but also the rate at which the flow temperature is increasing. If it goes up alarmingly fast the boiler assumes the worst.