Siemens LMV51 Series Basic Documentation page 270

270/301
Siemens Building Technologies
HVAC Products
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:
Load
60
Prohibited range
40
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 *
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).
Basic Documentation LMV5...
19 Addendum 4: LMV52... with O2 trim control and O2 module
Actual load
2 * delay time
Delayed actual load
τ
; access level: Service
CC1P7550en
13.08.2004
Time