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  • PID Cascade

    If temperature of heating element is measured, it is possible to increase stability of the heating system using two PID Smart Rules linked together (a.k.a. PID cascade).

    Comparison with simple hysteresis regulation:

    PID Cascade

    Hysteresis

    (/) smooth continuous regulation

    (X) slow start

    (/) fast start

    (X) oscillating regulation


    Example of using PID cascade in regulation of floor heating, measuring both - under-floor and ambient room temperature.

    Parameter

    Zone PID Smart Rule

    Floor PID Smart Rule

    Output actuator

    Thermostat for heating element
    0% ... 19 ºC
    100% ... 28 ºC

    Switch (relay)
    15 minute switching period

    Limit temperature

    Optional: By default is set to 10 ºC - 30 ºC.
    This can be changed in service settings of zone thermostat

    Optional: Floor temperature sensor
    Max. temperature 28º C

    Max. floor temperature allowed by hygienic standards is 28 ºC, however for heating purposes it is possible to use a few degrees higher temperature (e.g. 36 ºC), because temperature sensor is measuring temperature below surface.