LMSC one of the problems of having proportional and a positive value of B (temperature range at which the controller works as a p i d); Steaming power is reduced.
This is because when steaming the temperature of the boiler is always a degree or two below the setpoint, and that means the proportional value is always trimming down the power applied to the heating element because it’s near the set point and because B is a positive value it’s acting like a pid. This is exactly what we don’t want when steaming, we want the p&id really to act as a pure on off controller with no proportional limiting. On the early duetos where they started using the pid with shared parameters to control the steam boiler, steaming power was reduced by about 20% vs the earlier models which used a pressurestat. I’m assuming the change on the new Nurri might be to have three lots of pid parameters, in which case the steaming could probably be improved.