User's Manual
ANSI Electric Meter v3.1 User’s Guide 75
down at the time a demand reset was scheduled to occur, the demand reset data will
be recorded at the subsequent power-up with the timestamp of the power-up event.
You can also trigger a demand reset at any time manually by pressing the Demand
Reset push button on the meter front cover for 2 seconds and then releasing it, or by
using NES System Software. The Demand Reset button can be locked with a wire to
prevent it from being activated, as shown in Figure 1.1.
Reset Lockout Period
You can program a demand reset lockout period into the meter (measured in seconds). After a
demand reset has been performed, no subsequent demand reset of the same type can occur for the
programmed amount of time. The three types of demand reset are the push button reset, by
command via the optical port or power line channel, and through the TOU calendar.
Demand Interruptions
In general, any activity that interrupts or restarts the demand calculations results in
the end of the current interval, and the start of a new one. Both of these intervals
are classified as partial intervals by the meter. Their calculations are still performed
using the nominal interval time, and the end time of the new partial interval remains
synchronized to the hour. Examples of partial intervals are listed below:
Power failure. The demand for the previous interval is equivalent to the
energy measured from the start of the last main interval before the power
failed, to the time that that power failure occurred, divided by one main
interval duration. This will be computer after the meter is powered back on.
The demand for the present interval will be set to 0 after the meter is
powered back on, and demand calculations will resume normally.
A power failure demand lockout time can also be configured (in seconds) to specify how
long the meter should wait after powering up after a power failure before it starts making
demand calculations again.
Any demand reset, tier switch, absolute clock change, DST start and end, and
entry into (or exit from) test mode. The demand for the previous interval will
be set to the demand measured from the start of the interval to the time that
the interruptive event occurred, and the demand for the present interval will
begin measuring after the interruptive event has occurred.
End of Interval Display Icon
At the end of each demand main interval, an icon will display on the meter display
indicating that a demand interval has ended.
If a power failure occurs while this
icon is displayed, it will not be displayed until the next end of interval after the
meter is powered back on. For more information on the meter display, see
Reading the Display on page 1.