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6.6.2 Current Sensor Diagnostics
The load current must be at least 1% of the meter's rated load in order to use the
diagnostic function. Current sensor diagnostics can detect:
1. Reversed current sensors
2. Incorrect phase correspondence
3. Unusually low power factor (0.642 or lower)
CT Error: (ABC) is used to detect the swapping of current sensor phases. This
message could (in some rare cases) indicate a low (<65%) power factor condition. This
message may appear intermittently due to changes in line conditions. It should not be
on continuously. (See Section 6.4.1.)
NOTE: If you have connected the current sensor to all three terminals and the error
message is still appearing, reverse the black and white wires and repeat the
previous steps until the correct connection is found.
CT Error:
If the
message disappears, you have found the correct sensor connection;
however, the current sensor was not installed properly around the conductor, or the
sensor wires were extended and not spliced together correctly. Correct the sensor
installation, reconnect the black wire to the black terminal and the white wire to the
white terminal on the plug and reinstall the plug into the correct phase terminal for that
current sensor. The error message should disappear and the current sensor is now
installed properly.
CT Error:
If the
message does not disappear at any time while trying all 3 inputs both
ways, check the AC voltage input from the current sensor between the black and white
wires using an AC voltmeter. It will read approximately zero volts indicating that the
load current is very small (or zero) or the current sensors are not secured properly
(tight connection between core halves or lead splices not secure.)
Once the first current sensor is connected properly and the error message disappears,
repeat the previous procedure for the remaining two current sensors. When all error
messages have disappeared and all sensors are installed correctly, the meter is
operational.
6.7 RS-485 Wiring
RS-485 communication allows a computer or modem to communicate with one or
more Class 320 meters. You can connect as many as 52 meters along a 4000 foot RS-
485 cable run.
Class 320 Smart meters are available with your choice of communication options:
Modbus, BACnet, E-Mon Energy (EZ7) standard. There are two communication
protocols supported by the RS-485 connection; EZ7 and Modbus RTU. The protocol is
selectable via DIP switch S2, located on the Main Power Board. If S2 position 1 is in
the ON position, EZ7 is active. If S2 position 1 is in the OFF position, Modbus RTU* is
active. S2 position 2 is not used on the Class 320. DIP switch S2 positions 3 and 4 to
select the Baud rate for the RS-485 communications. See section 6.9.3 for details on
Baud rate selection. After changing the DIP switch positions, the CPU must be
rebooted by pressing S1 to activate the changes.
21
CLASS 320 METER
62-0397-02
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