WattMaster WCC III part 10 - Manual (Page 7)

10. RS-485 COMMUNICATIONS
WCC III Technical Guide 10-5
24VAC Power Wiring Considerations
You do not have to use the 24VAC connections on the Power
and Switchable RS-485 Communications Board, as each SAT
III panel should have its own 120VAC-to-24VAC transformer.
However, WattMaster Controls included the 24VAC connections
on the Power and Switchable RS-485 Communications Board as a
convenience option for 24VAC power distribution wiring.
When using the Power and Switchable RS-485 Communications
Board with a common 24VAC (250VA MAX) transformer,
the24VAC and GND polarity must be maintained on each and
every 24VAC & GND power connection.
•
Each SAT III draws - 15VA (No more than 15
SAT III max per board with a 250 VA - 24 VAC
transformer)
•
Each SAT 3C/D/F draws - 10VA (No more than
24 SAT 3C/D/F max per board with a 250 VA - 24
VAC transformer)
•
Each TUC-2R draws - 5VA (No more than 32
TUC-2R max per board with a 250 VA - 24 VAC
transformer)
•
Each TUC-5R draws - 8VA (No more than 28
TUC-R max per board with a 250 VA - 24 VAC
transformer)
•
External relays and contactors are not included, but
need to be considered for total VA draw.
PLEASE NOTE: Voltage loss in wire calculations must also
be considered and are listed below.
You must use the formula below when calculating max wire
distance and the resulting voltage loss that can and will occur
when running SAT III and TUC power wiring.
The formula is as follows: “VL” = “A” x “WR” x “DIF” x “2”
VL = Voltage Loss, A = AMP Draw, WR = Wire Resistance, DIF =
Distance In Feet, 2 = 2 Wires (1 Wire in each direction!)
24VAC Power Wiring
WIRE RESISTANCE STANDARDS
•
18-Gauge WIRE OHMS PER FOOT = 0.00639
•
16-Gauge WIRE OHMS PER FOOT = 0.00402
AMPERAGE CURRENT DRAW for WattMaster Controls
products
•
SAT III controller is 0.63 AMPS
•
SAT 3C/D/F controller is 0.42 AMPS
•
TUC-2R controller is 0.21 AMPS with actuator
•
TUC5-R controller is 0.34 AMPS
Example 1:
A single SAT III controller will have a voltage drop of 0.50 volts
with 100 feet of wire run when using 16-gauge wire. No more than
2 volts of drop is allowed for any WattMaster product. Two SAT
III controllers on the same loop will have twice the voltage drop
for the same distance.
0.506 Volts of loss = “0.63” x “0.00402” x “100 feet” x “2”
Example 2:
A single TUC-2R controller will have a voltage drop of 0.671 volts
with 250 feet of wire run when using 18-gauge wire. No more than
2 volts of drop is allowed for any WattMaster product. Two TUC-
2R controllers on the same loop will have twice the voltage drop
for the same distance.
0.671 Volts of loss = “0.21” x “0.00639” x “250 feet” x “2”
Example 3:
A single SAT 3C/D/F controller will have a voltage drop of 1.69
volts with 500 feet of wire run when using 16-gauge wire. No
more than 2 volts of drop is allowed for any WattMaster product.
Two SAT III controllers on the same loop will have twice the
voltage drop for the same distance.
1.689 Volts of loss = “0.42” x “0.00402” x “500 feet” x “2”