WattMaster WM-WCC3-TGD-01B - Manual (Page 453)

10. RS-485 COMMUNICATIONS
WCC III Technical Guide 10-1
SECTION 10:
RS-485 COMMUNICATIONS AND
TROUBLESHOOTING
__________________________________________
WCC III – MCD and SAT III Type
Controllers “RS-485 Network Loop”
Communications
The SAT III type controllers use a proprietary RS-485-based
protocol, and it is based on packetized data in predefi ned parameter
blocks. Troubleshooting of the SAT III type controllers’ RS-485
communications loop is possible with a Digital Voltmeter.
(The SAT II was based on Manchester encoded data, and was
very reliable, but was impossible to troubleshoot with a Digital
Voltmeter.)
For the WCC III - MCD system, WattMaster Controls has
developed a new, isolated RS-485 communication bus that
can support 239 SAT III type controllers on up to four separate
communications channels (loop connections). A single channel
(loop connection) can support up to 60 SAT III type controllers
on one communications loop. This is for redundant operation; if
an RS-485 communications channel goes down, it does not cause
other SAT III type controllers on the any of the other loops to lose
communications.
RS-485 Network Loop Communications
The maximum distance specifi ed for RS-485 communications
is 4000 feet. Using multiple channels (loop connections), it is
possible to go 4000 feet in one direction and 4000 feet in yet
another direction using the two communications channels (loop
connections) that are provided on the back of the standard WCC
III - MCD.
PLEASE NOTE: There are two physical RS-485 channels
(loop connections) on the back of the standard WCC III - MCD
computer. Two more physical RS-485 loops are available as an
option for larger loop sizes (WattMaster part PL101974).
This WCC III communications loop should also be thought of as a
major component of the WCC III system, not just a communications
loop that only connects SAT III type controllers to SAT III type
controllers. On this proprietary RS-485 communications loop, the
following commands are broadcast many times a second: Time,
Week Schedules, Global Binary, Global Analogs, Optimal Starts,
Overrides, PID programs, Duty Cycles programs, Proportional
programs, and Tenant Overrides. These commands are broadcast
from the WCC III - MCD to all of the SAT III Controllers and all
of the SAT 3C/D/F/P Controllers, as well as any TUC Controllers
that are connected to the SAT 3C/D/F Controllers. If your RS-485
communications wiring has a faulty or intermittent connection to
any of the SAT III type controllers, then a problem will result in the
proper operation of the WCC III system.