Beretta POWER PLUS Installation Instruction page 49

2 Attenuation_Low
Attenuation function for the LOW TEMPERATURE circuit (parameter 25).
This paragraph is similar to the previous one, however in this case referred to the low temperature circuit.
Two cases are possible:
- Operation with fixed set point, Par. 22=0
- Operation with climate control Par. 22=1.
OPERATION WITH FIXED SET POINT, PAR. 22=0
With attenuation in the low temperature circuit disabled, Par. 25=0, when the thermostat in the low temperature circuit
closes, the heating demand is signalled. When opening, the system stops.
The Master controller starts the pump in the low temperature circuit PZ3.
The set point for the low temperature circuit can be set on the Master controller, Setpoint_T_CH_low = Par. 3, pre-set
to 40°C in the range from 10°C to T_CH_Low_limit=Par. 23, in turn pre-set to 50°C.
The set point used will be the value set for parameter 3.
The burner is on when:
Manifold Temperature <=Set point – Start hysteresis.
The start hysteresis can be set, CH_Low_mod_hyst_on = Par. 26, pre-set to 5°C, between 0 and 20°C.
The Master controller converts the heating demand into an output requirement for each slave controller.
The burners are off when:
Manifold Temperature >=Set point + Stop hysteresis..
The stop hysteresis can be set (CH_Low_mod_Hyst_off=Par. 27, pre-set to 3, between 0 and 20°C).
When the attenuation in the low temperature circuit parameter is enabled, Par. 25≠0, the contact on the low tempe-
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rature thermostat is ignored, and a demand for heat in the high temperature circuit is present when:
Manifold Temperature <=Set point – Start hysteresis
The demand for heat stops when:
Manifold Temperature >=Set point + Stop hysteresis.
The set point in this case coincides with the value set for parameter 3 (Setpoint_t_ch_low) if the contact of the
low temperature thermostat is closed, while it is calculated as the value set for parameter 3 minus the attenuation
(Setpoint_t_ch_low-Attenuation_low) if the contact is open.
OPERATION WITH CLIMATE CONTROL, PAR. 22=1
If the attenuation in the low temperature circuit parameter is equal to 0, attenuation_low=Par. 25=0, behaviour is the
same as in the previous paragraph, except the set point is calculated according to the outside temperature.
If the outside temperature = T out_min=Par. 37, pre-set to 0°C, then set point =setpoint_T_Ch_low.
If the outside temperature = T out_max=Par. 38, pre-set to 18°C, then set point = T_ch_low_foot=Par. 24, pre-set to
50°C.
Between the two outside temperature values, the set point is calculated linearly.
Pre-set to 0.