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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 CascadeHysteresis

(tick) smooth continuous regulation

(error) slow start

(tick) fast start

(error) oscilating regulation

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

ParameterZone PID Smart RuleFloor PID Smart Rule
Output actuatorThermostat 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.