CHAPTER 2: INSTALLATION
INSTALLING THE SCAN TRANSPONDER
EPM 4
5
00 SUB METER – INSTRUCTION MANUAL
2–19
Z
Determine which of the transponders should have a telephone
modem, and order a telephone line to terminate at that point.
Do not proceed with the installation until the telephone line is
installed.
Z
After the telephone line is installed, install the scan transponder
with the modem next to the telephone line.
Install all three phases and the neutral to the transponder (see
Installation of Meter, MCI Board, and CTs
on page 2–15 for details).
Z
If there is more than one transponder, install the other
transponders and the interconnecting RS485 line, if required, which
links all of the transponders (go directly to
on page 2–15 if there is only one transponder in the
system or if each transponder in the system has a modem and
telephone line connection).
• An RS485 line is a pair of wires, AWG #20 or larger in diameter,
which begins at one transponder where a terminator is placed.
• The RS485 line runs from transponder to transponder ending at
the final transponder, where another terminator is placed.
• It is
critically important
that there should
never
be three RS485
pairs entering or leaving a transponder box.
• For the two transponders which have terminators, only one
RS485 pair leaves each box.
• For the other transponders, if there are more than two, exactly
two RS485 lines should leave the box: each line goes to another
transponder in the daisy-chain.
Only one modem should be installed in a data link system. If there
are two or more modems in a data link system, the transponders
will not communicate with each other.
• There may be no more than 32 transponders on a daisy-chain.
If there are more than 32, special care must be taken, which is
beyond the scope of these instructions.
Z
If possible, run the RS485 lines in a conduit to protect them from
damage.
Z
It is
critically important
to observe the polarity of the wires. The
RS485 data link uses a black and yellow color code. Match black to
black and yellow to yellow; otherwise the data link will not work.
Z
To test the data link, measure the DC voltage across the yellow to
black wire.
This should measure between 0.1 and 0.3 V. If it is negative or
outside of that range, re-check all of the transponder boxes
according to the above specifications.
