Watts tekmar 294 - Network and Communication Wiring; tekmarNet4 Boiler Bus Wiring; Boiler Expansion Wiring; Boiler Modbus Communication Wiring

IOM-T-294 2205 © 2022 tekmar
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tekmarNet4 Boiler Bus (Terminals 16, 17)
tekmarNet4 (tN4) is a wired communication network for tekmar thermostats, setpoint controls and snow melting controls to
communicate to the boiler control. The network provides central heating calls, DHW calls and setpoint calls as a digital message
between tekmar devices. This optimizes the heating system to operate more efficiently compared to on/off calls.
• The tN4 devices connect to the Boiler bus on terminals 16 and 17. The connection is polarity sensitive.
• Connect terminal 16 (tN4) to the tN4 terminal on the device.
• Connect terminal 17 (C) to the C terminal on the device.
Boiler Expansion (Terminals 18, 19, 20)
Ethernet (Terminal 24)
Boiler Modbus
®
Communication (Terminals 21, 22, 23)
The control operates 4 on board boilers and is expandable in groups of 4 up to a
maximum of 16 through the use of boiler expansions. The control connects to the
expansion through a wired three-wire connection. The maximum bus cable length is
100 feet (30 m) using 18 AWG solid conductor cable.
• Connect terminal 21 (-) to the boiler expansion terminal 1 (-).
• Connect terminal 22 (+) to the boiler expansion terminal 2 (+).
• Connect terminal 23 (Gnd) to the boiler expansion terminal 3 (Gnd).
The control can connect to the Internet through Ethernet.
• Connect the Ethernet RJ-45 port on terminal 24 to the building Local Area Network
(LAN) router or network switch using Category 5 cable.
The control can connect to select boilers that have an available Modbus communication
port to read the boiler’s error and lockout codes. The supported boilers are listed in the
Sequence of Operation section of this manual.
Use an 18 AWG Shielded Twisted Pair (STP) cable to connect the control to each
compatible boiler. The 294 operates as the bus master, and the boilers are member
devices. All boilers must use the same data rate, data type, parity bit, start bit parame-
ters as boiler 1. Boilers 1 to 16 are sequentially addressed 1 through 16.
• Connect the A (-) terminal on the boiler to the Modbus A (-) terminal 21.
• Connect the B (+) terminal on the boiler to the Modbus B (+) terminal 22.
• Connect the ground terminal on the boiler to the Gnd terminal 23.
Daisy chain wiring is recommended when connecting to multiple boilers.
18 19 20
Gnd
-+
Expansion
123
Gnd
-+
Expansion
21 22 23
Gnd
-+
Boiler Modbus
AB
Gnd
-+
Boiler 1
AB
Gnd
-+
Boiler 2
AB
RJ45
294 294EXP