Quadlogic MiniCloset-5c, Installation Manual, Page: 85 / 117

Appendix
© COPYRIGHT 2009
Quadlogic Controls Corporation
81
RS-485 Data Link Installation Guidelines
1. If there is more than one MC-5c, install the other MC-5cs and the interconnecting RS-
485 line, if required, which links all of the MC-5cs. See Figure A-2.
2. An RS-485 line is a pair of wires, AWG #20 or larger in diameter, which begins at one
MC-5c where a terminator is placed.
3. The RS-485 line runs from MC-5c to MC-5c ending at the final MC-5c, where another
terminator is placed.
4. It is critically important that there should never be three RS-485 pairs entering or
leaving a MC-5c box.
5. For the two MC-5s which gave terminators, only one RS-485 pair leaves each box.
6. For the other MC-5cs, if there are more than two, exactly two RS-485 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.
7. There may be no more than 32 MC-5cs on a daisy-chain. If there are more than 32,
special care must be taken, which is beyond the scope of these instructions.
8. If possible, run the RS-485 lines in a conduit to protect them from damage. It is
critically important to observe the polarity of the wires. The RS-485 data link uses a
black and yellow color code. Match black to black and yellow to yellow; otherwise the
data link will not work.
9. Avoid having loose conductors by using wire nuts to connect wires together. Use wire
nuts suitable for the wires’ gauge.
10. The data link should run no more than 4000 feet.
11. To Test the data link, measure the DC voltage across the yellow to black wire. This
should measure between 0.1V and 0.3V. If it is negative or outside of that range, re-
check all of the MC-5c boxes according to the above specifications.
RS-485 network problems are often caused by cabling issues which may be difficult to
troubleshoot. Complications include:

Inability to log in to a Quadlogic device.

Intermittent or no communication to a Quadlogic device.

Garbled characters appear on the terminal screen when logged into a Quadlogic device.
Listed below are guides that can help troubleshoot a faulty RS-485 network.

Make sure the meter is energized.

Make sure that there is voltage coming into the fuseblock of the Quadlogic device. It may
also be necessary to check if the fuses in the fuseblock are not yet blown.

Make sure the voltage plug is connected properly to the meterhead and communications
module.

Make sure the 4-wire communications cable is connected to the communications module
and the Quadlogic meter or Scan-Transponder head.

Make sure there is black tape covering the optical port window on meter.

Make sure that recommended wires were used.

Must use 2 Pair (Dual Twisted ONLY) wire with 24 AWG or thicker. Shield is not
necessary but if there is a shield, ground shield to metal housing at only of the
ends of the network. Do not connect at the other end or at midpoints.

Recommended wires are Belden 9842, Belden 3087A or Delco 43902.