Installation and Maintenance Manual

Startup
UNT-SVX07D-EN 101
In heating or cooling mode, the controller maintains the
zone temperature based on the active heating setpoint and
the active cooling setpoint, respectively. The active
heating and cooling setpoints are determined by the
occupancy mode of the controller.
For 2-pipe and 4-pipe changeover units, normal heat/cool
operation will not begin until the ability to conduct the
desired heating or cooling operation is verified. This is
done using the entering water temperature sampling
function, for which a valid entering water temperature is
required. When neither a hard wired nor a communicated
entering water temperature value is present on
changeover units, the controller operates in only heating
mode and assumes the coil water is hot. The sampling
function is not used.
The entering water temperature sampling function is used
only for changeover applications and for information and
troubleshooting. It does not affect the operation of the
controller. (For more information, refer to the following
section, “Entering Water Temperature Sampling Function
(UC400)”.)
Entering Water Temperature Sampling
Function (UC400)
The entering water temperature sampling function is used
with 2-pipe and 4-pipe changeover units and requires a
valid entering water temperature value. If the entering
water temperature value is less than 5°F (2.8°C) above a
valid zone temperature value for hydronic heating, and
greater than 5°F (2.8°C) below a valid zone temperature
value for hydronic cooling, the sampling function is
enabled. When the sampling function is enabled, the
UC400 controller opens the main hydronic valve to allow
the water temperature to stabilize. After 3 minutes, the
controller again compares the entering water temperature
value to the zone temperature value to determine if the
desired heating or cooling function can be accomplished.
If the entering water temperature value remains out of
range to accomplish the desired heating/cooling function,
the controller closes the main hydronic valve and waits 60
minutes to attempt another sampling. If the entering water
temperature value falls within the required range, it
resumes normal heating/cooling operation and disables
the sampling function.
Fan Operation (UC400)
The UC400 controller supports 1-, 2-, 3-speed fans and
variable-speed fans. The fan always operates
continuously while either heating or cooling during
occupied, occupied standby, and occupied bypass
operation. During unoccupied operation, the fan cycles
between OFF and HIGH, regardless of the fan
configuration. When running in AUTO mode, the fan
operates differently based on the mode and the type of fan.
For 1-, 2-, and 3-speed fans, each time the fan is enabled,
the fan begins operation and runs on high speed for a
period of time (0.5 seconds for fan coils and 3 seconds for
unit ventilators and blower coils) before changing to
another speed. Initially running on high speed provides
adequate torque to start the fan motor from the OFF
position.
Note: In occupied mode, the UC400 controller requires
continuous fan operation because of cascade zone
control. In unoccupied mode, the fan cycles.
Manual Fan Speed Control (UC400)
Regardless of the fan type, the fan runs continuously at the
desired fan speed during occupied, occupied standby, and
occupied bypass operation as follows:
• When the controller receives a communicated fan
speed signal (HIGH, MEDIUM, LOW)
• The associated fan speed switc
h is set to a specific fan
speed
• The Supply Fan Speed Request point is overridden
During unoccupied operation, the fan cycles between OFF
an
d HIGH, regardless of the communicated fan speed
signal or fan speed switch setting (unless either of these is
OFF, which in turn, will control the fan OFF).
The fan turns OFF when:
• The controller receives a communicated OFF signal
• The fan speed switch is set to OF
F
• Specific diagnostics are generated
• The default fan speed is set to OFF and the
fan is
operating in the AUTO mode
Note: The supply fan speed source
can be configured for
BAS, local, or default value control using the Tracer
TU service tool.
AUTO Fan Operation; 1-, 2-, 3-speed Fans
(UC400)
When the controller receives a communicated auto signal
(or the associated fan speed switch is set to AUTO with no
communicated value present), the fan operates in the
AUTO mode. In AUTO mode, the fan operates according
to the fan default (configurable using the Tracer TU service
tool). The fan speed has multiple speed configurations
(default is AUTO) or set to OFF for both heating and
cooling operation. When configured as AUTO (and with
multiple speeds available), the fan changes based on the
required capacity calculated by the control algorithm.
AUTO Fan Operation; ECM Energy Efficient
Mode (UC400)
When the controller is configured for Energy Efficient
Mode, by means of the Fan Operating Mode Request MV
point, the controller and daughter board will minimize
energy use by running the fan at the lowest possible speed
while maintaining space temperature. The controller will
fully utilize valves, economizer, or electric heat which
increases fan speed to meet space temperature (unless the
fan has been manually controlled. Refer to the preceding
UNT-SVX07_-EN.book Page 101 Friday, April 27, 2012 9:40 AM