71
16.3.2 Water supply control (P141 = 2)
If heating mode is selected with a water-to-water unit, the setpoint is adjusted based on the temperature measured by the hot water supply
sensor. If cooling mode is selected and P6 = 1, the setpoint is adjusted based on the temperature measured by the heat exchanger outlet
sensor. If P6 = 2 in the same mode, it is adjusted based on the temperature measured by the manifold sensor.
The type of control used is PID
τ.
The temperature is measured periodically (
τ) then compared to the setpoint and multiplied by a proportional coefficient (P) -- taking into
account the difference between the measurement and the setpoint (D) and the change in the difference between the measurement and the
setpoint (I) -- in order to approach the setpoint quickly.
Formula: DV = P (M-S) t1 +
(M-S)*I + [(M-S) t0 - (M-S) t1]*D
M = Measurement, S = Setpoint.
When P146 = 0 and P147 = 0 (standard setting), the PID
τ function becomes PT (the Integral and Derivative functions are disabled)
The related parameters are as follows:
P251: Calculated setpoint
P121: Setpoint 1 in cooling mode
P123: Setpoint 1 in heating mode
P145: P coefficient
P146: I coefficient
P147: D coefficient
P148: T coefficient
In cooling mode:
A call is made for an additional stage if:
DV > +1.0 K for the first stage and +0.5 K for the additional
stages.
A call is made to turn off a stage if:
DV <
–0.5 K for a stage and –1.0 K for the last stage.
Example: Two-stage unit with a 5°C setpoint, where D = 0 and I = 0.
In heating mode:
A call is made for an additional stage if:
DV <
–1.0 K for the first stage and -0.5 K for the additional stages.
A call is made to turn off a stage if:
DV > +0.5 K for a stage and +1.0 K for the last stage.
Example: Two-stage unit with a 45°C setpoint. I = 0 and D = 0.
16.3.3 Adjusting the setpoint to the water supply with compensation on the water return (P141 = 3):
Aim:
Allow the control system to anticipate changes in load on the loop by monitoring for variations in the water inlet temperature.
Action:
Adjusts the controller time delay.
Principle:
The water return temperature is measured:
θt0; evaporator in cooling mode, condenser in heating mode at time t0 then t0 + P151.
The calculated temperature variation [
θt1 - θt0] is used to define the compensator coefficient.
The PID control polling time then becomes: remaining time × compensator coefficient.
Configuring the compensator coefficient: The compensator coefficient can be set to between 0.1 and 1 (parameter P150).
- If the compensator coefficient = 1
→ the function is disabled.
- If the water return temperature variation < 0.5°C
→ no compensation.
The compensator coefficient is maximum when the temperature variation = 10°C between each time.
.
P
Stage 1
Stage 2
Stage 1
Off
On
0.5
3
4
6
7
1
4
4.5
5.5
6
1.5
4.33
4.66
5.33
5.66
2
4.5
4.75
5.25
5.5
P
Stage 1
Stage 2
Stage 1
On
Off
0.5
43
44
46
47
1
44
44.5
45.5
46
1.5
44.34
44.66
45.33
45.66
2
44.5
44.75
45.25
45.9
S U P P L Y T E M P . : - x x . x °
S E T P O I N T : - x x . x °
Содержание Magister 2 Series
Страница 2: ......
