Operating Instructions 29
RQ_NORMAL, RQ_UPDATE_STATUS, and RQ_REPORT_MASK requests are supported. You can
make a request of the entire meter with using the
NodeObject
or one of the functional blocks.
In response to each request, the object’s status is returned in
nvoStatus
. The status variable
nvoStatus
also indicates if the request was made of an invalid object number, or if the object
doesn’t support the request made of it. The meter supports the following status fields:
●
object_id
: The number of the object whose status is being reported (0 = NodeObject).
●
invalid_id
: Indicates that a request was made with an invalid object number.
●
invalid_request
: Indicates that the object does not support the requested operation.
nviTimeSet
The date and time are set with
nviTimeSet
. The meter uses the date and time to synchronize
demand measurements to the hour, and to timestamp peak demand. You can read the meter’s
current date and time by reading this variable. The meter only sets
nviTimeSet
to the nearest five
seconds and only updates the value every five seconds.
The WattNode Plus internal clock is accurate to ±4 minutes per month, so you may want to
update
nviTimeSet
once a day or once a week.
nviTimeSet
may be updated by a monitoring
computer or it may be bound to a separate clock node on the network. The meter stores the cur-
rent date and time in non-volatile memory every five seconds, so after a power failure, it resumes
with the date and time from before the power failure.
Tampering with
nviTimeSet
can affect the timing of demand measurements that may be used for
billing. To prevent unauthorized tampering, authentication can be enabled for
nviTimeSet
.
nviFileReq / nvoFileStat / nviFilePos
These file transfer network variables are used by LNS
®
network management tools to configure
the meter. These variables should never be directly manipulated by the operator.
nviResetEnergy
The energy variables
nvoEnergySum
,
nvoEngyPosSum
,
nvoEnergyA
,
nvoEnergyB
,
nvoEnergyC
, and
nvoReacEngySum
are all reset to zero kilowatt-hours whenever “1” is
written to
nviResetEnergy
. As a security measure, two variables—
nvoEnergySumNR
and
nvoEngyPosSumNR
—are non-resettable.
If you wish to make sure energy cannot be accidentally reset or reset by an unauthorized person,
enable LonTalk authentication for
nviResetEnergy
. See
for details.
Energy Variables
Commonly known as kWh (kilowatt-hours), the energy is the integral of power over time. Many
installations will only use the energy measurement. It is commonly used for billing or sub-meter-
ing. Because energy is an accumulated value, it can be used on networks that are accessed
infrequently (like a utility meter that only needs to be read once a month). All energy variables are
preserved through power failures.
All energy SNVTs are reported as a SNVT_elec_kwh_l with a resolution of 0.1 kWh. All energy
registers wrap around to zero when they reach 100,000,000 kWh (100 GWh) or negative 100
GWh (only some energy registers allow negative values).
During a power outage, the energy consumed will not be measured. Whenever the line voltage
drops below 60–80% of nominal, the meter will shut down until power is restored. To preserve the
energy measurement across power outages, the meter writes the energy to non-volatile memory.
When power returns, the last stored value is recovered.
For bidirectional applications, such as installations with PV panels, the WattNode meter measures
the net energy sum:
nvoEnergySum
can count both up and down, depending on whether you
are consuming (importing) or generating (exporting) energy. The WattNode meter also provides
