Johnson Controls
5513350-JTG-1018
The control system for the NexusPremier
™
is fully self-
contained. To aid in unit setup, maintenance, and opera-
tion, the unit controller is equipped with a user interface
(UI) that has a 5 row × 35 character organic light-emitting
diode (OLED) display. The OLED display presents plain
language text in a menu-driven format to facilitate use.
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Controls
General
Changeover Sensor
The controller compares this temperature against a set-
point to determine whether to place the unit in heating,
cooling, or satisfied mode. Zone temperature or RAT—or a
BAS input—can be used as the changeover sensor.
Mandatory Sensors
The following sensors are required to make the unit oper
-
ate and are included as standard on every rooftop.
• Discharge Air Temperature
• Return Air Temperature
• Outside Air Temperature
Optional Sensors
Depending on the application, additional sensors may be
required.
•
Zone air temperature
•
Zone humidity
•
Enthalpy sensor (for use with economizer)
•
Dual enthalpy sensors (measures enthalpy of outdoor
air and return air; used with economizer)
•
Supply duct pressure (VAV units)
•
Building pressure (required for exhaust/return fan)
•
Carbon dioxide (CO
2
) (required for demand ventilation)
•
Smoke detector
Warm-up/Cool Down Methods
The warm-up/cool down feature supports four methods
of initiating the warm-up/cool down mode: occupied com
-
mand, schedule, optimal start, or coast.
Occupied Command
With an occupied command, the supply fan turns ON for a
5-minute stabilization period, after which the RAT sensor
compares to the warm-up setpoint. If the value is equal to
or below the warm-up setpoint, heating is controlled to the
warm-up DAT setpoint. If the value is above the warm-up
setpoint, the control goes into occupied mode. Warm-up
stays active until the RAT sensor is above the warm-up
setpoint for 5 minutes or the early start period expires. The
control goes into occupied mode thereafter. Cool down op
-
erates opposite of warm-up, using cooling instead of heat
-
ing stages.
The unit controller can be connected to and operated by a
building automation system (BAS). In addition, hard wired
control options to the unit controller are provided using a
BAS interface board.
The unit controller uses the latest technology and provides
complete control for the unit along with standard BACnet
®
MS/TP and BACnet IP, Modbus
™
, and N2 communications.
The unit controller also has a USB flash drive that can be
used to capture historic data on unit operation and to up-
date firmware.
Unit Mode
Unit Type
The controller supports two rooftop types: variable air vol
-
ume (VAV) and single zone VAV (SZVAV). Both types can
be configured to operate in several different modes of oc-
cupancy, temperature control, warm-up/cool down, and au
-
tomated demand response.
Occupancy Modes
Depending on the application, the controller can be in-
dexed between occupied, unoccupied, optimal start, or
coast modes of operation. These occupancy modes are ini-
tiated automatically via an internal time clock or externally
from a BAS command, hard wired input, or tenant override
via zone sensor.
Sensors
Temperature Control Sensor
The controller compares the discharge air temperature
(DAT) against a setpoint to determine the heating or cool
-
ing demand. On multi zone VAV units, the DAT setpoint can
be reset by different methods: fixed, outside air temperature
(OAT), supply fan speed, external control, zone, or return air
temperature (RAT). See also
.
