OBJECTIVE
This technical information details the new PID cascade algorithm that can be selected within the OpenTherm page of the RegConfig Configurator.
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The following image shows, within the OpenTherm page of the RegConfig, the position of the Heating Cascade Algorithm Control section and the Secondary Heating Temperature Compensation section, closely related to the PID cascade algorithm:
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The cascade algorithm can be of three types:
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Attenzione: non utilizzare G0 in quanto è il generatore OpenTherm utilizzato con il prodotto DOT, non con il sistema REG, quindi nella logica di cascata non viene mai considerato.
Warning
Do not use G0 as it is the OpenTherm generator used with the DOT product, not with the REG system, therefore it is never considerate in the cascade logic.
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However, it is important to underline that “PID Cascade” and “Buffer Tank Compensation Temperature” are two different and separate functions, which can operate together or separately (e.g., the “Buffer Tank Compensation Temperature” can be also used for other types of cascade algorithms, and also for Parallel functioning), which incidentally “share” the same sensor, as the requirement for both algorithms is to monitor the “final” temperature provided by the group of generators.
Note
The “Buffer Tank Compensation Temperature” is not the subject of this technical part, which instead focuses on the “PID Cascade”.
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so, if we consider a delta T of 4 K and a delay T of 5 minutes before switching on a second generator, then the value of Pid I to be entered is 87 (1740 / 4 * 5). The lower the Pid I parameter, the more time will pass before an additional generator is added.
Note
The values 160 and 1740 were derived from formulas implemented for this specific algorithm!
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The result of the settings made is displayed at the top right of the OpenTherm page “Generator Demand Status”:
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Enable/set Heating: if the square is ticked, this means that there is a request to the generators and in the rectangle on the right is indicated the required set point. For heat pumps, the set point is either heating or cooling. If the square is not ticked and the set point is zero, this means that no demand is coming from the circuits to OpenTherm.
Enable/Set DHW: if the square is ticked, this means there is a request to the generators and in the rectangle on the right is indicated the required set point for the production of Domestic Hot Water. If the square is not ticked and the set point is zero, this means that no demand is coming from the circuits or the DHW page to OpenTherm.
N. active generators (cascade): indicate how many generators have been activated for the cascade in heating or cooling (not for DHW production).
The last rectangle at the bottom (yellow box) is the countdown of the Stop between changes in hundredths of a second.
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Always referring to the image in the Generators section of the OpenTherm page:
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si fa presente quanto segue:
la produzione di Acqua Calda Sanitaria non risponde all'algoritmo di cascata PI;
l’algoritmo PI accende i generatori OpenTherm in base alla priorità inserita e in base alla richiesta selezionata in terza colonna (Solo Riscaldamento, solo Raffrescamento o Sempre).
Nella parte inferiore della pagina OpenTherm si riporta per ogni generatore il risultato delle richieste di riscaldamento/raffrescamento e ACS (riquadro rosso) e il feedback dai generatori verso il sistema REG (giallonote the following:
Domestic Hot Water production does not respond to the PI cascade algorithm;
PI algorithm switches on the OpenTherm generators according to the priority entered and according to the request selected in the third column (Only Heat, Only Cool or Always)
The lower part of the OpenTherm page shows for each generator the result of the heating/cooling and DHW requests (red box) and the feedback from the generators to the REG System (yellow):
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Evidenziato in rosso si trova:
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Si ipotizza di avere selezionato 1 come numero di generatori Start e Minimo, mentre il numero Massimo è 9:
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L’impianto in oggetto ha 4 generatori OpenTherm:
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