Cold Request Generation - Mitsubishi Electric s-MEXT-G00 006 Technical Manual

TM_s-MEXT_ME28relC_00_12_19_EN
5.2

COLD REQUEST GENERATION

The external unit control logic requires DIP temperature control. This logic operates as follows.
+
Setpoint
-
The control variable is the ambient or delivery temperature and the controlled variable is the adjustment ramp (define 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 Master PAC-IF
card. The Master PAC-IF card will then send the capacity request to any connected Slave PAC-IF cards.
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.
In view of the long wait between two variations of request to the Master PAC-IF card, there is a time delay of 5 seconds before sending a power variation, to make sure that
the value is the actually requested value, and not subjected to transitional and sudden request variations.
Technical manual
P
∑ Error
D
Figure 5-3: PID control logic operation
1 2 3 4
0%
Figure 5-4: Step subdivision logic operation
Figure 5-5: Time scale logic operation
K e ) (t
p
t

 
I
∑
K e ( ) d
t
0
de ) ( t
K
d
dt
5 6 7 8 9 10
75
Process Output
11
Cooling request
100%
TRANSLATION OF THE ORIGINAL INSTRUCTIONS