WattMaster WCC III part 13 - Manual (Page 14)

WCC III Technical Guide 13A-12
13. WCC III - MCD INSTALLATION GUIDE
The WCC III System RS-485
Communication Wiring
The WCC III - MCD can communicate with up to 239 satellite
controllers via a two-wire RS-485 communication loop. On the
back of the WCC III – MCD there are two RS-485 communication
loop ports that come as standard. Each one of these communications
loop ports can communicate with up to 60 satellites for a total of
120 satellites.
Two more additional RS-485 communication loop ports can be
added at an additional cost for any WCC III system that has more
than 120 satellites. The two-wire RS-485 communication loop
should be stranded 2 wire twisted pair of 18-gauge wire with a
shield wire, and it also must be plenum rated were applicable.
The use of stranded wire is mandatory to ensure a good connection
with the ¼ inch Sta-Con connectors which are used to terminate
the wires at the satellite controllers. The RS-485 communication
wire does not have to be run from each satellite controller back to
the WCC III – MCD, but rather the RS-485 communication wire
can be “daisy-chained,” which means that only one twisted pair of
wires is connected to each of the WCC III - MCD communications
loops. The maximum allowable length of wire from the WCC
III - MCD to the farthest satellite is 4000 feet per RS-485
communications loop.
NOTE: A length greater than 4000 feet is allowed under
certain circumstances. Consult the factory for assistance if the
communications loop required for your application will exceed
4000 feet.
The RS-485 wire specifi cations are generally a stranded 18-
gauge - 2 wire twisted pair with shield. 18-gauge stranded wire is
mandatory to ensure a good connection with the ¼ inch Sta-Con
connectors, which are used to terminate the wires at the WCC III
- MCD and at the satellite controllers. The old SAT II Manchester
communications loop was supposed to have used a 2-wire twisted
pair with shield, but this was not used in every installation. This
old SAT II communications loop should not be used for the new
SAT III communications loop. A new RS-485 communications
loop should be ran to each new replacement SAT III controller.
The shield wire must be used on the new SAT III controller, as
it provides a “ground” reference for the RS-485 communication
loop. WattMaster Controls sells two versions of 18-gauge - 2-wire
twisted pair with shield communications wire— (1) WattMaster
part #WR-NL-WR-18 which is marked “Network Loop” with a
red stripe for rapid identifi cation. This connection is intended to
run from the WCC III – MCD to the SAT III, SAT 3C/D/F, SAT
3P, and then to the next SAT 3 type controllers. (2) WattMaster part
# WR-LL-WG-18 which is marked “Local Loop” with a green
stripe for rapid identifi cation for the TUC loops that run from the
SAT 3C/D/F controllers out to the TUC controllers.
“Wire Nuts” on the RS-485 communications loop should be avoided
at all costs. As an alternative to the “Wire Nuts”, WattMaster
Controls has a Power and Switchable RS-485 communications
board, and the WattMaster part number is PL102224. This Power
and Switchable RS-485 communications board can be thought of
as a 24-VAC power and communication distribution system for
the SAT III communications loop, and this board will aid in initial
startup and future troubleshooting of the SAT III communications
loop. These boards should be used on a fl oor-by-fl oor basis. This
Power and Switchable RS-485 communications board is also
available in a small metal electrical enclosure.
The wire that makes up the communication loop should be
shielded. Shielded cable has an aluminum jacket over the wires
that could act as an “antenna” to carry away any “stray” electrical
signals that could interfere with the communication process. The
shield should be grounded throughout the SAT Loop.
<<<LOCAL LOOP>>> AZWR-LL-WG-18>>> E76191 CL2P 18AWG (UL) 012112 FT
<<<NETWORK LOOP>>> AZWR-NL-WR-18>>> E76191 CL2P 18AWG (UL) 012112 FT
WATTMASTER LOCAL LOOP WIRE
WATTMASTER NETWORK LOOP WIRE
Figure 4 WattMaster Controls various communications loop wire
RS-485 Communication Wiring