The buffer lower control is a PD control, while the buffer upper sensor control is a P control where the:
The lowest output value of the two control loops will be a control signal that results in a faster heating up of the domestic hot water.
The lower sensor measures the load immediately when the buffer lower water temperature decreases due to the cold water supply. Therefore the PD control responds immediately to this temperature drop.
Both buffer water temperature sensors have their own individual control as shown in the next figure. The P-band of both controllers is one half of the parameter UWT-01 and the D-time of the buffer lower temperature controller is defined by the parameter LWT-02. The effective (lowest) control signal is the minimum value of the DHW upper and lower control signals.
Fig. 3. DHW Continuous Control
NOTE: |
For this control type we recommend to set the P-band UWT-01 to a value of 10 K, see Start-up Hints. |
Table 3. Parameter List
Description |
Range |
Default |
Units |
UWT-01: P-band buffer temperature control |
1...20 |
5 (change to 10 K) |
K |
LWT-02: D-time buffer temperature control |
0...1000 |
0 |
sec |
SST-01: temperature difference primary/ secondary system |
0...60 |
10 |
K |