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5.1.4
Cold request generation
The external unit control logic requires DIP temperature control. This logic operates as follows.
+
Setpoint
∑
-
The control variable is the return or delivery temperature and the controlled variable is the adjustment ramp (defined in values
from 0 to 100%). The higher the ramp value, the higher the request sent to external units.
It is also possible to enable fan modulation, together with speed change, in order to improve system adjustment.
The request of cooling capacity, calculated by the s–MEXT unit (0–100%) using the DIP adjuster, will then be converted into 11
request steps and sent to the Client PAC–IF card. The Client PAC-IF will then send the capacity request to any connected
Server PAC-IF.
Req.
OFF
During the operation of the PAC-IF card, the passage through the steps is sent in accordance with the following time scales:
•
5 min if the last step forwarding was equal or lower than 5 (in relation to the already active power)
•
10 min if the last step forwarding exceeded 5.
The following chart shows the way the above time scales work.
Version 38
P
I
Error
K
D
Figure 5-3: PID control logic operation.
1
2
3
4
5
0%
Figure 5-1: Step subdivision logic operation.
Figure 5-5: Time scale logic operation.
K
e
) (t
p
t
∑
e
(
)
d
t
0
de
) (
t
K
d
dt
6
7
8
9
10
11
100%
Process
Output
Cooling request
139
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