Trane BCHE Installation, Operation And Maintenance Manual page 68

Installation - Controls
WARNING
Hazardous Voltage!
Failure to disconnect power before servicing could
result in death or serious injury.
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Verify that no power is
present with a voltmeter.
WARNING
Proper Ground Connection Required!
Failure to follow instructions below could result in
death or serious injury.
After installation, ensure that the 24 Vac transformer
is grounded through the controller. Measure the
voltage between chassis ground and any ground
terminal on the controller. Expected result: Vac <4.0
volt.
NOTICE
Equipment Damage!
Sharing 24 Vac power between controllers could
result in equipment damage.
A separate transformer is recommended for each UC400-B
controller. The line input to the transformer must be
equipped with a circuit breaker sized to handle the
maximum transformer line current.
If a single transformer is shared by multiple UC400-B
controllers:
• The transformer must have sufficient capacity.
• Polarity must be maintained for every UC400-B
controller powered by the transformer.
Important: If the polarity is inadvertently reversed between
two controllers powered by the same
transformer, a difference of 24 Vac will occur
between the grounds of each controller, which
can result in:
• Partial or full loss of communication on the
entire BACnet MS/TP link
• Improper function of the UC400-B
controller outputs
• Damage to the transformer or a blown
transformer fuse
Transformer Recommendations
A 24 Vac power supply must be used for proper operation
of the binary inputs, which requires 24 Vac detection. In
addition, the spare 24 Vac outputs may be used to power
relays and TRIACS.
• AC transformer requirements: UL listed, Class 2 power
transformer, 24 Vac ±15%, device max load 24VA. The
transformer must be sized to provide adequate power
68
to the controller (12VA) and outputs (maximum 12VA
per binary output).
• CE-compliant installations: The transformer must be
CE marked and SELV compliant per IEC standards.
Wiring Requirements
To ensure proper operation of the UC400-B controller,
install the power supply circuit in accordance with the
following guidelines:
• A dedicated power circuit disconnect switch must be
near the controller, easily accessible by the operator,
and marked as the disconnecting device for the
controller.
2
• 18 AWG (0.823 mm ) copper wire is recommended for
the circuit between the transformer and the controller.
Important: The controller must receive AC power from a
dedicated power circuit; failure to comply may
cause the controller to malfunction. DO NOT
run AC power wires in the same wire bundle
with input/output wires; failure to comply may
cause the controller to malfunction due to
electrical noise.
Connecting Wires
Figure 60. Grounding the controller
1 2 3 4 5
J15
Alternate
Phoenix
Ground
Method
24 Vac
Transformer
To connect the wires:
1. Disconnect power to the transformer.
2. Connect the 24 Vac secondary wires from the
transformer to the 24 Vac and terminals on the UC400-
B controller (refer to the illustration above).
3. Do one of the following to ensure the controller is
adequately grounded:
Connect a grounding pigtail at some point along the
secondary wire that runs between the controller
terminal and the transformer.
Connect a grounding pigtail at some point along the
secondary wire that runs between the controller
terminal and the transformer.
Note: A pigtail connection may be necessary between
earth ground and/or enclosure ground if the device
is not grounded through one leg of the transformer
wiring.
6 1 2 3 4 5 6
J16
Phoenix
BCX-SVX002A-EN