12. BACnet®
Page 55
PRODIGYT M2 UNIT CONTROLLER
12. BACnet
®
12.1. M2 BACnett Module
The optional M2 BACnet Module allows communication between the Lennox M2 (M2, version 6.00 and higher) and a BAC-
net MSTP network. The BACnet module conforms to the BACnet application specific controller (B−ASC) device profile. A
Lennox non−communicating zone sensor, a BACnet network zone sensor, or a BACnet thermostat may be used to send the
zone temperature or thermostat demands to the M2.
NOTE − A qualified systems integrator with adequate training and experience is required to integrate and commission the
M2 BACnet into a third−party BACnet Building Automation System. A BACnet network configuration software tool is re-
quired to commission the BACnet network.
Refer to the Installation Instructions for the M2 BACnet Module for installation. Refer to the Service Literature for the M2
BACnet Module for data point and programming information.
M2 SYSBUS NETWORK
CONNECTION
BACnet
TRANSMIT
& RECEIVE
LEDS
Figure 29. M2 BACnet Module
12.2. Recommendations
1. Set all BACnet devices on an MS/TP network to consecutive MAC addresses, starting at 1, so that there are no gaps
between MAC address values.
2. Set Max_Master device property on all devices to match the largest MAC address on the network. Note, this could be
larger than existing network to allow for adding devices to the network with out the need to adjust the Max_Master prop-
erty.
3. Use ReadPropertyMultiple service instead of ReadProperty service when reading multiple analog inputs or values
12.3. Default Settings
device Max_Master = 127
device Max_Info_Frames = 1
device Object_Identifier = MAC address
device Object_Name = Lennox_M2" + MAC address
device Location = US"
device Description = Lennox HVAC Controller"
baud rate = 38.4k
(terminated)(terminated) (not terminated) (not terminated)
CONTROLLER/
ROUTER
(not termi-
nated)
(not termi-
nated)
(not terminated)
(terminated per mfg
instructions)
The configuration shown above has terminations on the
M2 BACnet modules at both ends and ONLY at both ends
of the chain.
The configuration shown to the right has a termination at
the controller/router on one end and a termination at the
M2 BACnet module on the other end; terminations are
ONLY at the ends of the chain.
Cable type − twisted pair with shield, 22 awg minimum,
Belden #88761 or #8761 (Lennox 27M19, 94L63, 68M25).
CONTROLLER/
ROUTER
(not terminated) (terminated)
(not termi-
nated)
Figure 30. Terminating ends of daisy−chained networks
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