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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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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la richiesta di R = Riscaldamento, A = ACS e C = Condizionamento;
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Highlighted in red you have:
The demand for H = Heating, W = DHW, and C = Cooling;
The required temperature in heating or cooling [°C];
la potenza richiesta in riscaldamento o raffrescamento The power required in heating or cooling [%].
Se il generatore viene chiamato per la sola produzione ACS sia la temperatura richiesta che la potenza sono a zero, i valori che vengono passati in caso di produzione ACS sono quelli che si visualizzano in Stato Richiesta Generatori (in alto a destra nella pagina OpenTherm). If the generator is used for DHW production only both the required temperature and power are zero, the values that are passed in case of DHW production are those that are displayed in Generator Demand Status (top right of the OpenTherm page)
La pagina OpenTherm può gestire sia caldaie mediante protocollo OpenTherm (senza firmware dedicato) sia pompe di calore o caldaie mediante protocollo Modbus con firmware dedicato. In giallo si evidenziano i valori trasmessi dalla caldaia o dalla pompa di calore e sono strettamente legati a come il produttore dei generatori ha implementato il protocollo OpenTherm sulla caldaia o il protocollo Modbus sulla pompa di calore/caldaia (fare sempre riferimento alla documentazione del generatore a riguardo o nel caso di firmware dedicati alla documentazione fornita con il firmware). Passando con il mouse sopra i vari rettangoli/quadrati compare un tag con una descrizione estesa:
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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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