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Siemens Building Technologies
Basic Documentation LMV5...
CC1P7550en
HVAC Products
6 Temperature or pressure controller (internal load controller LC)
13.08.2004
6.4.3 Multistage control
When selecting «Oil» as a fuel, the LMV5... must be set to «2-stage» or «3-stage», de-
pending on the type of burner used, using parameter «Operation Mode» (refer to sec-
tion 5.4
→
«Operating mode»).
In these 2 operating modes, the PID algorithm is not required and will not be calculated.
The 2 or 3 fuel stages are activated and deactivated depending on the actual values,
the parameterized switching differentials_Stage1...3 (refer to subsection 5. 4. 1) and
the parameterized reaction thresholds Q2 and Q3.
This approach is used to reduce the switching frequency of the higher stages.
−
The integral of the control deviation over time is generated
−
Switching on of stage 2 will be locked until the temperature has dropped below the
adjustable reaction threshold Q2
−
Switching on of stage 3 will be locked until the temperature has dropped below the
adjustable reaction threshold Q3
Parameter:
ThreshStage2On (Q2), ThreshStage3On (Q3)
Reaction thresholds Q2 and Q3 (integral of control deviation (K) x time (s))
If the temperature often drops below the switching on thresholds, the integrals will be
added up and the higher stage switched on when the associated Q-value is reached.
If, before that, the setpoint is reached with the lower stage, the counter will be reset.
General
Load-dependent activation
of the higher burner stages