Bulletin 100-50-5.1 – Page 11
Figure 5 - RS-485 Wiring
Controller 1
GND
R
T
R
T
Communication
Master
A B
B
Controller n
R
T
- Termination
resistor
B
A
Controller n-1
GND
B
A
AGND
Setup
The Sporlan Superheat Control can be networked to com-
municate process variables back to a master controller. This
information can be used for verifying system performance or
updating individual setpoints via RS-485 and PC interface.
Data can be accessed remotely through the master controller.
For further information on remote monitoring, see the docu-
mentation for the master controller.
Prior to connecting the network, each controller must be
assigned a separate address on the Modbus or BACnet net-
work, Addr. Refer to Section 3 – Setpoint Menu Operation to
enter the Setpoint menu. Once in the Setpoint menu, scroll to
Add and assign each controller on the network an individual
Communication
Master
Figure 6 - Daisy Chain
Network Configuration
address. Note that no two controllers can have the same
address. Default address for each controller is ‘1’.
NOTE: Add is the controller’s RS-485 address and CAd is
the controller’s display address.
RS-485 Connection Requirements
See Figure 5 - RS-485 Wiring.
Wire Type: Use Belden 8760 or equivalent
Maximum Number of Network Nodes: 100
Maximum Run Length: 4000 ft
Recommended Network Configuration: Daisy Chain, a
single continuous transmission line from one end to the other.
Other configurations involving triple-lug connections, such as
star, are not recommended. See Figure 6.
Noise Reduction: Termination resistance (R
T
in Figure
5) is recommended to reduce reflections and noise on the
data transmission lines. Place the resistance at the extreme
ends of the cable, with the resistance value matching the
characteristic impedance of the transmission line (typically
120 ohms for twisted pair cables).
Shielding prevents noise from EMI sources. If the cable is
shielded, connect the shield to earth ground at one end only.
NOTE: Do not connect shield to RS485 GND.
Keep RS485 wiring away from high voltage AC lines to
reduce noise and data errors on the communication lines.
RS485 communication cable should be placed perpendicular
to AC lines at any intersection.
Grounding: Connect a third conductor to RS485 GND (ter-
minal 13) to prevent ground potentials between nodes. This
conductor should be included in the shield of the twisted pair
cable to prevent noise. NOTE: Do not connect RS485 GND
to earth ground.
Third Party Controllers: To avoid nuisance “network
errors”, the use of third-party controllers on the same RS485
network with Sporlan controllers is not recommended.
Refer to the documentation supplied with the communication
master for additional RS485 network requirements.
7. PID Tuning
If temperature pull down is satisfactory, then the default
control scheme (supermarket mode) should be used. The PID
values may be adjusted if superheat is not stable. If super-
heat is oscillating around setpoint at steady state conditions,
reduce PID settings to half of existing values. If pull down is
not satisfactory, then the Superheat Control can be configured
into a standard PID scheme that can be fully adjustable. This
feature can be accessed by entering the Setpoint Parameters
Menu as described in Section 3. Go to parameter SvPS, super-
market mode, and change its value to FF.
NOTE: Only experienced professionals should access
this feature. System stability and performance may be
improved by adjusting PID.
The Superheat Control is factory programmed with default
Proportional–Integral–Derivative (PID) settings that will
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