Patent EP-0108699-B1 (EP)
IPC: F24D3/00
Filed: 1983-11-03
Granted: 1988-01-20
Abstract: 1. Process for bi-energetic central heating, the circuit (3) of which comprises radiators (4), a circulating pump (5), a room thermostat (20) and a mixing valve (22), of the type in which two boilers (1, 2) connected in series to the central-heating circuit (3) are used, namely : an electrical boiler (1) equipped with electrical resistors (27) and with a first aquastat (10) which, during the periods with a favourable electricity tariff level, causes the activation (or cut-out) of the resistors (27) for temperatures of the water of the heating circuit Tee (for activation) and Tce (for cut-out) ; a boiler (2) operating on an energy different from electricity, called a second-energy boiler, equipped with a burner (14) and with a second aquastat (11) which limits the temperature of the water leaving this second-energy boiler (2) and which, during the periods with a high electricity tariff level when this boiler (2) operates alone, causes the activation (or cut-out) of the burner (14) of this boiler (2) ; and in which these two boilers (1) and (2) are controlled by means of an electrical control box (15) connected to the said aquastats (10, 11), to the burner (14), to the resistors (27), to the circulating pump (5) and to a system (17, 18) which detects the change in tariff level of the electrical energy and which has a device making it possible to define and take into account a predetermined time constant t, in which process : on the one hand, one or other of these two boilers (1) and (2) is activated automatically as a function of the tariff level of the electrical energy detected by the system (17, 18) and as a result of the change in the thermal demands made on the heating circuit which is detected by the said aquastats (10, 11) as a function of the temperature of the water of the heating circuit (3) ; on the other hand, the power of the electrical boiler (1) does not make it possible to meet all the thermal demands during the period when the electricity is at a favourable tariff level, whereas the power of the second-energy boiler (2) is capable of meeting all the thermal demands on the coldest days, and finally, the second-energy boiler (2) is activated or not only after the said predetermined time t, characterized in that, during the periods with a favourable electricity tariff level : first of all, the second-energy boiler (2) is activated together with the electrical boiler (1) when, after this predetermined time t, the temperature of the water of the heating circuit detected by a third aquastat (12) located on the outlet line (7) of the electrical boiler (1) acting on the burner (14) of the second-energy boiler (2) via the box (15) is below or equal to a predetermined threshold temperature T, itself below : on the one hand, the temperature of the water of the heating circuit Tee, causing the activation of the resistors (27) of the electrical boiler (1), detected by the first aquastat (10), and, on the other hand, the temperature of the water of the heating circuit, causing the activation of the second-energy boiler (2), detected by the second aquastat (11), then, from the moment (F) when this second-energy boiler (2) has thus been activated, the burner (14) of this second-energy boiler (2) is cut out via the box (15), when the third aquastat (12) detects, on the outlet line (7) of the electrical boiler (1), a water temperature Tcf, at which it causes the cut-out of the burner (14) of the second-energy boiler (2), this temperature Tct being below : the temperature of the water Tce, causing the cut out of the resistors (27) of the electrical boiler (1), detected by the first aquastat (10), and the temperature of the water, causing the cut out of the burner (14) of the second-energy boiler (2), detected by the second aquastat (11) ; then, if after this second-energy boiler (2) has thus been cut out (G), the temperature of the water falls again (M), without the electrical boiler (2) having previously been cut out, the second-energy boiler (2) is reactivated via the third aquastat (12) and the box (15), when the threshold temperature T is reached (N), without taking the said predetermined time t into account, finally, still in the period with a favourable electricity tariff level, when the second-energy boiler (2), after being reactivated (F) or (N) and then cut out (G), when the temperature of the water at the outlet of the electrical boiler (1) reaches its cut-off temperature Tce (J), the first aquastat (10) causes the operational cut-out of the resistors (27), as soon as this situation arises and from this moment, the second-energy boiler (2) can now be reactivated via the box (15) when the threshold temperature T is reached, only if, after the predetermined time t, the temperature of the water of the heating circuit in line with the third aquastat (12) is still below or equal to this threshold temperature T.