Appendices
Appendix F - Measuring Consumption (kWh), Demand, and Other Applications
64
Siemens Industry, Inc.
125-201
09/30/2019
Another variation of these applications is to create a PPCL which captures energy
consumption (for example, daily, hourly) in a single virtual point. This virtual point can
be trended and building operators can use the Insight Dynamic Plotter to monitor
dynamic and/or historical energy consumption.
NOTES:
1.
The slope and intercepts of %X%CMH and %X%CML are the same as
accumulator points (%Z%, %Y%).
2.
The slope (that is, resolution) for monthly readings should be determined by
identifying the maximum billed consumption or using the following equations
(assume PF = 1.0):
kWref = (CTref. Amps × Voltsref)/1000
for 1-Phase Power
kWref = (CTref. Amps × Voltsref × SQRT(3) × PF)/1000
for 3-Phase Power
kWh = kWref * 24 hours/day × 31 Days
for kWh per Month
kWh = kWref * 24 hours/day × 7 Days
for kWh per Week
● For firmware revisions earlier than 2.0, do not use the $LOC resident point for
intermediate calculations; the maximum value of the $LOC resident point is 32,767.
Maximum
Physical Unit (V2)
Slope
(Resolution)
Intercept
(V1)
32,766.00
1
0
327,660.00
10
0
163.83
0.05
0
1638.30
0.5
0
163,830
5
0
1,638,300
50
0
32,766.00
1
0
Measuring and Calculating Demand (kW)
DEMAND represents the instantaneous 3-phase total demand (kW) and functions as a
logical analog input. In applications where the demand fluctuates, increase the COV
parameter for DEMAND to reduce COV traffic. If the power meter is reading whole
building kW, the largest number of COVs occurs when the building transitions from
unoccupied to occupied status. For example, using a 300A power meter with a COV
limit of 0.064 results in changes of values being observed for every change greater
than 0.064 kW (such as every time a 1.0 HP motor, one 100W light bulb, or a personal
computer is energized).
In general, select the COV for the kW based on the range of the CT. For example, if a
1% COV is needed for a 300 Amp service (300 Amps × Sqrt (3) × 480V/1000 = 249.6
kW ), select a COV of the slope × 20 (provides a COV every 0.064 slope × 20 kW =