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Appendices
Appendix F - Measuring Consumption (kWh), Demand, and Other Applications
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Siemens Industry, Inc. 125-201
09/30/2019
1.28 kW). Unless a very high resolution is required, a COV limit of slope × 20 is
adequate for most applications.
The following table lists kW loads for various motor horsepower ratings:
Horsepower kW Horsepower kW
1 0.746 10 7.46
2 1.49 25 18.86
5 3.73 50 37.3
Trending Data
If scheduling trend data at the Insight workstation, schedule data collection at regular
intervals. Size the field panel trend definition appropriately to prevent trend data from
being lost due to roll over. Select the number of samples based on field panel memory
and network traffic limitations. It is possible to upload trend data to the workstation
using the full trend buffer option or by a scheduled collection time.
Collecting Energy Data
Many methods can be used to collect data for energy monitoring, reporting, and
controlling applications. These methods vary based on intended application, desired
accuracy, and field panel memory requirements. The best tradeoff between accuracy
and field panel memory requirements is to trend the kWh values every 15 minutes
(trend both CONSUMPTN LO and CONSUMPTN HI points). Use this data to calculate
total consumption for various time-of-use periods and also to calculate the average
demand over a 15-minute period. In this case, DEMAND is used for only real-time load
monitoring applications (graphics, alarming, and so on) and does not need to be
trended. Applications requiring greater accuracy for demand billing or allocation
purposes can collect peak demand calculations with timestamps using the rolling or
fixed demand methods. In projects where field panels have severe memory limitations,
the 15-minute interval can be extended to 30 or 60 minutes with generally acceptable
results.
Peak Demand Limiting
Electric utilities base their charges to commercial users on a combination of total
electricity used during the billing period (known as consumption, kWh and the peak
electrical demand required to meet the need of the facility (known as demand, kW).
The utility determines the demand charge of a facility by continually measuring
electricity usage for successive short time intervals (usually 15 minutes). The highest
demand (average kW) during one of these intervals becomes the basis for the demand
charges. Since 40% or less of an electric bill can be based on demand charge, it is
beneficial to limit the peak electrical demand of the facility.
The following PPCL can be used for peak demand limiting applications:
00010 C ELECTRIC SUBMETER
00012 C THE SYSTEM WILL BE DDC CONTROLLED USING ELECTRIC ACTUATION.
00014 C NOTICE: ALL ACTUATORS ARE SET UP IN THE PROGRAM TO WORK AS 0% - 100%