EN - 42
The parameters that determine when the other stages turn on and off remain managed by each machine.
The value of P806 will have to be selected based on machine 1 in order to achieve an operating order similar to the start-up of the last stage
(see figure previous page).{
• Control in parallel with "setpoint offset":
COMPRESSOR 1
COMPRESSOR 2
COMPRESSOR 1
Machine 1 adjusts itself to the master machine's setpoint. Machine 2's setpoint is shifted by the value of P805.
Thus, machine 2's setpoint is machine 1's se P805.
►
Water return control for storage (P154 on master machine = Yes):
This type of control makes it possible to generate a maximum amount of capacity during a given period, often when electricity is cheapest.
Both machines are turned on at an interstage time delay of 10 seconds when P122 + P155 is achieved. The machines are shut off at P122 at an
interstage time delay of 1 second.
- If P154 = Yes, storage control is enabled and the control mode based on the selected setpoint is controlled by the master machine.
Cascade control is used by default for both machines when setpoint 1 selected (standard control).
The 'Yes' value of P154 on the slave machine becomes inaccessible if P28 = Yes.
►
Time schedules:
If P27 = Yes, the programming of two parallel-connected machines will be controlled by the control parameters on the master machine and the
time schedule on the slave machine will become inaccessible.
17.5 Unit status menu
If there are no general faults and the automatic operation inputs are closed, a submenu (overrides the fault message) is added to the unit status
menu.
17.6 Management of pumps using P811 (pumps stopped by control):
If P811 = No:
- No pumps are turned off by the control (default value).
If P811 = Yes except for one:
- If P801 = No (no backup machine), only the pumps on one machine are stopped by the control. The pumps on the last machine running must
remain on until it is turned off by the control.
- Only the pump on the machine that has run the least remains on (important: this pump is started back up before the pump on the other
machine is stopped).
If P811 = Yes machine stop:
- The pumps on both machines are stopped by the control (all the protections except for water flow rate are maintained).
This implies that the customer controls one or more pumps that circulate the water through both machines.
18. CONTROLS
18.1 Main control in cooling and heating modes
Control principle:
The temperature of the chilled water or hot water is monitored and checked against the setpoint value in order to control the compressor and the
capacity control slide valve. The controlled temperature is measured on the evaporator (cooling mode) and the condenser (heating mode).
The controller uses a variable pulse width modulated (VPWM) batch PID algorithm.
M A S T E R S L A V E C T R L
M A S T E R M A C H I N E
S L A V E M A C H I N E
P805
MACHINE STAGE
MACHINE STAGE
Machine STP
Machine STP
50
10
50
10