MERLIN NX IP AND MST/TP VAV CONTROLLER - INSTALLATION INSTRUCTIONS
13
EN1Z-1076GE51 R0722
POWER SUPPLY
General Information
To prevent a risk of injury due to electrical shock and/or
damage to the device due to short-circuiting, low-voltage
and high-voltage lines must be kept physically separate. To
prevent a risk of short-circuiting and damage to your
MERLIN controller, do not reverse the polarity of the power
connection cables and avoid ground loops (connecting one
field device to several controllers).
Before wiring the controller, determine the input and output
device requirements for each controller used in the system.
Select input and output devices compatible with the
controller and the application. Consider the operating
range, wiring requirements, and environmental conditions
while selecting input and output devices.
Determine the location of controllers, sensors, actuators,
and other input and output devices and create wiring
diagrams for illustrations of typical controller wiring for
various configurations.
The application engineer must review the control job
requirements. This includes the sequences of operation for
the controller and the system as a whole. Usually, some
variables must be passed between the controllers that are
required for optimum system-wide operation. Typical
examples are the TOD, occupied, unoccupied, outdoor air
temperature, demand limit control signal, and the smoke
control mode signal. Understanding these interrelationships
early in the job engineering process is vital for proper
implementation while configuring the controllers.
NOTE:
All wiring must comply with applicable electrical
codes and ordinances. Refer to job or manufacturers’
drawings for details. Local wiring guidelines (for
example, IEC 364-6-61 or VDE 0100) may take pre
-
cedence over recommendations provided in these
installation instructions.
To comply with CE requirements, devices having a
voltage of 50-1000 VAC or 75-1500 VDC but lacking
a supply cord, plug, or other means for disconnecting
from the power supply must have the means of dis
-
connection incorporated in the fixed wiring. This type
of disconnection must have a contact separation of at
least 1/8 in. (3 mm) at all poles.
Power Wiring
All wiring must comply with applicable electrical codes and
ordinances, or as specified on installation wiring diagrams.
Controller wiring is terminated to the screw terminal blocks
located on the device.
NOTE:
For multiple controllers operating from a single trans
-
former, the same side of the transformer secondary
must be connected to the same power input terminal
in each controller.
NOTE:
Power must be off prior to connecting or removing
connections from the 24 VAC power (24 V~ / 24 V0),
and 20 VDC power terminals.
Use the heaviest gauge wire available, up to 18 AWG
(1 mm2), with a minimum of 22 AWG (0.3 mm2), for
all power wiring.
NOTE:
When connecting power, ensure that one leg of the
24 VAC secondary circuit and the grounded terminal
on the device are connect to a known earth ground at
the panel or enclosure. Limit the distance of the
power wire run between the device and the trans
-
former to 15 feet (4.5 meters and restricted for same
room installation).
The transformer must be UL Listed for smoke control.
The transformer also needs to be mounted and
installed in an enclosure.
CAUTION
CAUTION
A single transformer can power more than one
controller.
Fig. 14 on page 14
shows the power
wiring details for multiple controllers. Controller
and configuration are not necessarily limited to
three devices, but the total power draw, including
accessories, cannot exceed 100 VA when
powered by the same transformer (the U.S. only).
