Emerson E2 Power Monitoring, Holiday Schedules, Temporary Schedule Events, Overlapping, Ranges

11.14.1.3 Temporary Schedule Events

Each schedule may also be given up to three pairs of temporary schedule events. These events start and end at specific days and times and do not continue past those dates (in other words, temporary events cannot be made to occur weekly or annually).

11.14.1.4 Overlapping

Events may, and often do overlap within a schedule. When events overlap, the E2 uses the following priority structure, from highest to lowest:

1.Temporary Schedule Event #1

2.Temporary Schedule Event #2

3.Temporary Schedule Event #3

4.Events that occur on HD1 (Holiday #1)

5.Events that occur on HD2 (Holiday #2)

6.Events that occur on HD3 (Holiday #3)

7.Events that occur on HD4 (Holiday #4)

8.Temporary Schedule Events of a slave schedule’s master schedule (if applicable).

9.Standard events within the schedule itself.

11.14.1.5 Ranges

In addition to the 15 events within a master or slave schedule, up to 12 standard ranges may be specified. Ranges are sets of dates that specify which days within the year the schedule’s events will be applied. The E2 checks the list of ranges to see if the current date falls within any of the twelve possibilities; if the date does not fall within a range, none of the schedule’s events will occur.

When no date ranges are specified, the schedule is con- sidered to be active. All scheduled events will occur nor- mally.

11.14.2 Holiday Schedules

A Holiday Schedule application’s primary function is to pass along the day of the week to one or more master or slave schedules, and to tell these schedules when it is a holiday (HD1 - HD4). A holiday schedule determines hol- idays by cross-referencing the current date with its user- programmed list of holiday date ranges. During the time periods of these date ranges, the holiday schedule tells the schedules to perform the events programmed for one of the four holiday dates (HD1, HD2, HD3, or HD4).

Because multiple E2s on a network would likely use the same holiday schedules for determining special occu- pied and unoccupied building hours, holiday scheduling is handled by Global Data. This means the holiday schedule can be set up in one E2 and shared with all other E2s that use time scheduling.

11.15 Power Monitoring

A Power Monitoring application is used primarily for monitoring, recording, and to a lesser degree controlling KW usage in a building.

11.15.1 Overview

Explanation of “Demand”

Power companies supply power to consumers at a fixed rate per kilowatt hour until a pre-defined level of energy consumption is reached. This level is called the demand limit. When the demand limit is exceeded, the rate is greatly increased as a penalty for high power demand by the consumer. Generally, once the demand limit is exceeded, the increased rate is charged for the remainder of the year.

To determine if you have reached the demand limit, the power company arbitrarily monitors a consumer’s energy consumption for a fixed period of time. This monitoring period is called a demand window. Power companies can generally tell you how long a demand window period lasts, but you’ll never know when the measurement will take place.

How Power Monitoring Calculates Demand

To help you make sure you do not use more power than the demand limit, the E2’s Power Monitoring applications determine your current KW usage in much the same way as your power company. Power Monitoring uses a watt- hour transducer input to determine the current KW usage. Multiple KW values are averaged together into “demand windows,” much like the ones power companies use.

Then, depending on how the application is configured, the most current KW value is compared to a demand set- point. The “current KW value” in this case may be either the instantaneous value read by the power transducer, or it may be the average of all KW transducer readings taken over 1-minute intervals. This setpoint should be equal to or slightly lower than the demand limit set by your power company.

In short, since E2 doesn’t know when the power com- pany’s demand window will begin, the E2 measures power as if the demand window could happen at any time. This way, E2 can more accurately determine when your site is approaching or exceeding the demand limit.

Shed Mode

If the KW usage is higher than the demand setpoint, Power Monitoring goes into Shed Mode. During Shed Mode, Power Monitoring turns on a digital output called SHED OUT. This output may be connected to the demand shed inputs of one or more E2 applications, which will in turn shut down or otherwise curb the power usage of the

11-44 • E2 RX/BX/CX I&O Manual 026-1614 Rev 4 5-JAN-2013