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Siemens Building Technologies
Basic Documentation LMV5...
CC1P7550en
HVAC Products
19 Addendum 4: LMV52... with O2 trim control and O2 module
13.08.2004
19.4.6
Behavior in the event of load changes
If the system identifies a load change, the O2 trim controller will be locked.
Release criterion:
40
60
Time
Load
Prohibited range
Pa
ra
m
e
te
r:
Lo
ad
C
o
n
tr
o
lle
rL
o
c
k
Pa
ra
m
e
te
r:
Lo
ad
C
o
n
tr
o
lle
rLo
c
k
Actual load
Delayed actual load
2 * delay time
75
50
d3
8e
/0
8
04
As illustrated above, based on the actual load, a ”delayed actual load“ will be mapped.
This delayed actual load reflects the delay of the flue gas values resulting from the iner-
tia of boiler operation. If the load difference between actual load and delayed actual
load exceeds a certain adjustable limit, a load change will be detected. When the dif-
ferential drops below the limit again, another waiting time of 2 * delay time will be added
before the contoller is released.
The limit of the load difference can be set by the user:
Parameter:
LoadCtrlSuspend
Setting range 0-25 %; presetting: 5 %; access level: Service
The delayed actual load will be mapped via a PT1 member with an adjustable time
constant:
Parameter:
FilterTimeLoad
Setting range 4-10; presetting: 5
⇒
5 *
τ
; access level: Service
The parameter denotes the period of time on completion of which the next load change
in the form of
LoadCtrlSuspend
can be made. If a load change is detected, the O2
value will be increased (offset).