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Appendices
Appendix F - Measuring Consumption (kWh), Demand, and Other Applications
59
Siemens Industry, Inc. 125-201
09/30/2019
Appendix F - Measuring Consumption (kWh), Demand,
and Other Applications
The kWh reading has been split into two points to provide an accurate reading.
CONSUMPTN LO (Point 8) and CONSUMPTN HI (Point 9) are accumulators that
totalize kWh. The sum of CONSUMPTN LO and CONSUMPTN HI provides the total
accumulated kWh for all three phases. These points are always increasing and cannot
be reset or commanded to zero. The CONSUMPTION LO point counts up until it
reaches a value of
10000 , then resets automatically and stars counting up again.
CONSUMPTION HI is always counting up. It increases by increments of 1 each time
CONSUMPTION LO resets to
0 , after counting up to 10000.
Calculating Total Consumption Example
Conceptually, the total consumption for any time period is the difference between the
reading taken at the start of the time period and the reading taken at the end of the
time period. Use the following calculation technique to retain accuracy for calculating
total consumption. In this method, the difference (that is, end
– start) for accumulator
points is taken before summation of the total consumption.
Since CONSUMPTION HI only counts up by 1 for every 10,000 counts for LOW
CONSUMPTION, it should be multiplied by 10,000 before CONSUMPTION LO is
added to obtain the TOTAL CONSUMPTION. The following example, where total
consumption for the months of January and February are calculated, illustrates this
point.
((HILAST
– HISTART) × 10000)
+ (LOLAST
– LOSTART)
= CONSUMPTION PERIOD
January ((28
– 13) × 10000)
+ (9200
– 7000)
= ((15 × 10000) + 2200) = 152200
February ((48
– 28) × 10000
+ (1400
– 9200)
= ((20 × 10000)
– 7800) = 192200
The following PPCL reads the MD-P1 and MD-P2 accumulators at the start of the
specified time period (for example, month, week, and day) and stores them in virtual
analog points. To calculate the consumption for a specified time period, a test is
conducted where the most recent (that is, last) accumulator value is tested against the
low accumulator reading taken at the start of the time period. The resulting calculated
value can be displayed on an Insight graphic to assist building operators in monitoring
the energy consumption in their facilities.
00010 C ENERGY MANAGEMENT PROGRAM TO CALCULATE MONTHLY, WEEKLY AND DAILY USAGE
00012 C
00030 C THIS SOFTWAWRE IS OWNED AND MAINTAINED BY SIEMENS BUILDING TECHNOLOGIES, INC.
00032 C ALL RIGHTS RESERVED. ANY MODIFICATIONS WITHOUT THE EXPRESS, WRITTEN
00034 C CONSENT FROM SIEMENS BUILDING TECHNOLOGIES, INC. MAY VOID THE WARRANTY.
00036 C