TEC2145-4 N2 Networked Thermostat Controller with Single Proportional Output and One-Speed Fan
Control Installation Instructions 7
Connecting the N2 Bus
To connect the N2 Bus:
1. Set the N2 address of the TEC2145-4 Thermostat
Controller per the engineering drawings prior to
wiring the thermostat controller. (See the Com
addr parameter in Table 4 to set the N2 address for
the thermostat controller.) Also, test for N2 voltage,
polarity, and isolation prior to wiring the thermostat
controller.
Note: Pressing and holding the UP/DOWN arrow
keys simultaneously displays the device address
that is assigned.
2. Observe the polarity when connecting the N2 Bus
wires to the thermostat controller.
3. After the N2 Bus wires are connected to the first
thermostat controller, continue in a daisy-chained
fashion to the next thermostat controller.
Note: The N2 Bus wiring must be twisted-pair
lines. Do not run the N2 Bus wiring in the same
conduit as line voltage wiring (30 VAC or above) or
other wiring that switches power to highly inductive
loads (such as contactors, coils, motors, or
generators).
For more N2 Bus overview information, refer to the
N2 Communications Bus Technical Bulletin
(LIT-636018) and the ASC and N2 Bus Networking and
Troubleshooting Guide Technical Bulletin
(LIT-6363003).
N2 Write, Override, and Release Commands
N2 overrides take priority over any local adjustment or
command in the thermostat controller until the override
is released. For example, if the supervisory controller
sends an N2 override message to turn System Mode
Off and then the user selects System Mode On at the
thermostat controller keypad, the thermostat controller
keeps the System Mode Off.
When an N2 override is released, the object may once
again be changed through the thermostat controller
keypad. The thermostat controller does not retain any
data entered at the thermostat controller keypad during
the override.
The thermostat controller automatically releases all N2
overrides after 10 minutes of no communications. For
example, if the network cable is removed from the
thermostat controller or if the supervisory controller
goes offline.
The thermostat controller does not maintain an internal
command priority table. The most recent command
received by any of the Object Types listed in Table 2
controls the thermostat controller.
However, if the Metasys system sends an N2 write
command to turn System Mode Off and the user
selects System Mode On at the thermostat controller
keypad, the thermostat controller keeps the System
Mode On.
Handling Setpoints
If a setpoint is overridden, the thermostat controller
adjusts the other setpoint to maintain the minimum
deadband between the setpoints, if necessary. The
setpoints can be spread farther apart but can never be
adjusted closer than the current minimum deadband
value.
• The value for Heating SP (ADI-3), Unoccupied
Heating SP (ADI-5), and Standby Heating SP
(ADI-10) must stay within the limits for Minimum
Heat SP (40°F / 4.5°C) and Maximum Heat SP
(ADI-14).
• The value for Cooling SP (ADI-4), Unoccupied
Cooling SP (ADI-6), and Standby Cooling SP
(ADI-11) must stay within the limits established in
the controller by Minimum Cool SP (ADI-15) and
Maximum Cool SP (100°F / 37.5°C).
Failure to stay within the limits for a command results in
an N2 Negative Acknowledgment (NAK) error from the
thermostat controller.
N2 Device Mapping
Metasys® System Person-Machine Interface (PMI)
Define the N2 thermostat controller as a Vendor Device
(VND) when adding the thermostat controller to the
supervisory controller.
Do not direct-map any points; instead, run control of
these points through the Control System (CS) object.
The supervisory controller Model Point Type is the
definition inside the model file. Use a CS object to
retrieve the data.
Metasys System Extended Architecture
The Controller Point Type is the fixed-point definition
inside the controller. Refer to the N2 Integration with
the NAE Technical Bulletin (LIT-1201683) for more
information on Controller Point Types.
Network Automation Engine (NAE) Setpoint
commands translate into N2 Write commands. NAE
Operator Override and Release Operator Override
translate into N2 Override and Release commands,
respectively.
You must not have a Relinquish Default for the
setpoints if you want to change them from the
thermostat controller display.
