User Manual

CM2U8567E / 04.1999 VISONIK DCS Functions and System Messages VVS18 Siemens Building Technologies
2-188 Function MXD Landis & Staefa Division
[kWh]
T
1
T
2
9370Z53E
STOL
EMAX
TTOL
Shed load Connect load
OFLM = OFF Limit
Tolerance band
(Selected from MXD register)
ESTM for T
2
ONLM = ON Limit
MD
TPER
(e.g. 15 mins.)
ESTM for T
1
Time
MD
(t) Energy consumption within the current Integrating period
TPER
Integrating period in minutes
ESTM
(t) Estimated energy to the end of the integrating period
STOL
Initial tolerance for determining the tolerance band
TTOL
Target tolerance for determining the tolerance band
The maximum demand program runs in the background, gathering necessary regulating
data from the maximum demand point
As soon as the effective energy consumption MD lies outside the tolerance band, MXD
calculates:
•
the regulator output variable, i.e.,
–
the amount of load to be shed, or
–
the amount of load that can be reconnected,
so that at the end of the integrating period the effective energy consumption is smaller
or, as a maximum, equal to the EMAX setpoint.
The regulator output variable calculated is then compared with the load entered in the
maximum demand load register. DCS is then required to execute the relevant switching
commands on the basis of the above priorities.
The MXD function processes exclusively the maximum demand register addressed
above. MXD has no further functionality of its own. Execution is provided by maximum
demand programs running individually for each maximum demand point.
Explanation:
The maximum demand
program
The MXD function