MegaControls NT50 Series Manual

RS-485 Modbus RTU Room Thermostats with LCD for Fan Coil Units
Features
■
Ultra slim wall-mount unit to match
any décor
■
Supports Modbus RTU protocol
■
Supports standalone operation on RS
-485 communication failure
■
Fan coil application database pre-
loaded
■
Large easy-to-read Liquid Crystal
Display (LCD), with LED backlight
■
A stylish bi-directional rotating dial
and two compact touch keys to
provide ease of operation
■
Choice of constant display of ambient
temperature or temperature set point
value
■
Output relays employed for direct
connection of valve actuators and 3-
speed fan
■
Configurable operating parameters
■
Choice of ºC or ºF temperature
display via parameter setup menu
■
2-wire on-off, 3-wire floating and 0(2)-
10 VDC output models available
■
Adjustable proportional band and
integral time for 3-wire floating and 0
(2)-10 VDC output models
■
Choice of valve stroke time for 3-wire
floating output models
■
Field adjustable high and low
occupied set point limit settings
■
Field adjustable cooling and heating
unoccupied set point values
(applicable to some models only)
■
Choice to retain last entered settings
on power resumption
■
Dual-output on-off and 0-10 VDC
models with auto cooling/heating
changeover (deadband operation)
and manual override
■
Choice of operating sequence for dual
-output models
■
Adjustable 1 to 5 K deadband for dual
-output models
■
Unoccupied mode capability with field
adjustable cooling and heating set
points, not available to "1M", 1AM"
and "1FM" models.
■
Choice of unoccupied mode activation
in operating mode only or in both
standby and operating modes
■
Provides one additional digital input
for function such as remote night
setback, service/filter alarm or motion
Copyright © Mega Controls Limited
NT50 Series
detection
■
Choice of fan action in unoccupied
mode
■
Choice of auto fan action in heating
mode
■
Field recalibration capability of
measured temperature
■
Continuous or auto fan operation
■
External and seasonal changeover
temperature sensor capability
■
Optional infra-red remote control unit
■
Optional special faceplate color
available on request
General
The NT50 Series RS-485 networking
room thermostats use the
communication technologies of Modbus
RTU protocol to monitor and supervise
fan coil units in the heating, ventilating
and air-conditioning industry, and
employ a simple master/slave protocol.
All NT50 Series thermostats are slaves
in this protocol, and can be under the
control of a Mega Controls BACnet
gateway, of either BMG or BMGE
Series, called the master. The BMGs
and BMGEs are native BACnet devices
and communicate using the BACnet
MS/TP or BACnet-over-Ethernet
protocol.
Net 2 port of the BMG master and all
slaves are daisy-chained through a RS-
485 Modbus RTU network. The
maximum number of NT50 slaves in a
Modbus RTU network is 32.
Each BMG has 2 addresses. Net 2
address is always 0 which is the
address of the Modbus RTU network.
Net 1 address is the MAC address of
the BACnet MS/TP network which is
also set up for a maximum of 32
devices in a trunk cable length not
exceeding 1000 m. The BMG gateway
spontaneously detects the presence of
slaves that go online in its NET 2
network.
If more than 32 BMGs are needed in the
system, an additional BACnet system
device is required for the second
BACnet MS/TP network.
Each BMGE gateway is available with
two RS-485 networks. Each network
Issue Date November 1, 2023
can support up to 32 NT50 Series
Modbus RTU devices. The BMGE
gateway spontaneously detects the
presence of slaves that go online in
its NET 1 and NET 2 networks.
The NT50 Series thermostats cover
a wide range of fan coil applications,
including 2 and 4-pipe fan coils and
direct connection to 3-speed fans.
Temperature sensing can be from a
built-in room sensor or a remote
sensor.
A fan-speed control touch key
allows control of a 3-speed fan. The
speed control key has 4 positions:
"Hi-Med-Low-Auto". In the "Hi",
"Med" or "low" position, the fan runs
continuously at the selected speed.
In the "Auto" mode, the fan speed is
temperature dependent and
controlled automatically at 2 K
differential increments from low to
high speed.
Mounting
The thermostats can be flush
mounted or secured to a standard
European 75 x 75 x 47 mm (strongly
recommended) electrical box. See
Fig. 2: Mounting Details. Two
mounting screws are included .
Ordering
To order, specify complete model
numbers.
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