Exhaust Control; Valve Operation; Operation; Calibration - Trane BCHE Installation, Operation And Maintenance Manual

Start-Up
temperature (unless the fan has been manually controlled.
Refer to "Manual Fan Speed Control," p.
stages of electric heat exist the controller will use a single
minimum air flow for each stage.

Exhaust Control

Exhaust control is achieved by a single-speed exhaust fan
and controlled by binary output 2 (BO2). Exhaust control, if
not present, can be enabled by selecting Yes under the
Exhaust Fan Selection on the Tracer
page under the Equipment Options group.
Note: Exhaust fan configuration cannot be selected with 3-
speed fan operation.
Important: If exhaust control is added to an existing
configuration, all other configuration options
should be verified to match the correct
equipment options.Temperature and flow
setpoints will revert to default values.
The exhaust function is coordinated with the supply fan and
outdoor/return air dampers as follows:
• The exhaust fan energizes when the fan is running and
when the outdoor air damper position is greater than or
equal to the exhaust fan enable position (or the outside
air damper position at which the exhaust fan turns ON).
• The exhaust fan turns OFF when the fan either turns
OFF or the outdoor air damper closes to 10 percent
below the exhaust fan enable position.
• If the exhaust fan/damper enable setpoint is less than
10 percent, the exhaust output is energized if the
outdoor air damper position is at the setpoint and de-
energized at 0.

Valve Operation

The controller supports one or two 3 wire modulating, two-
position or field supplied 0-10V valves, depending on the
application (refer ). The controller opens and closes the
appropriate valve(s) to maintain the active zone
temperature setpoint at the heating setpoint in heating
mode or the cooling setpoint in cooling mode (refer to
Cascade Zone Control in "Zone Temperature Control," p.
108).
Controllers used for 2pipe applications support heating,
cooling, or heat/cool changeover with a single valve/coil. A
controller used for 4-pipe applications supports cooling or
heat/cool changeover with a main valve/coil and heating
only with an auxiliary valve/coil.
Three-Wire Modulating Valve Operation
Two binary outputs control each valve: one to drive the
valve open and one to drive the valve closed. The stroke
time for each valve is configurable using the Tracer
service tool. The controller moves the modulating valve to
110
109. If multiple
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TU Configuration
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the desired positions based on heating or cooling
requirements.
Three-Wire Modulating Valve Calibration
Modulating valve calibration is automatic. During normal
controller operation, the controller overdrives the actuator
(135 percent of the stroke time) whenever there is a
request for a position of 0 percent or 100 percent. At either
power-up, after a power outage, or when the occupancy
status changes to unoccupied, the controller first drives all
modulating valves (and dampers) to the closed position.
The controller calibrates to the fully CLOSED position by
over driving the actuator (135 percent of the stroke time).
Thereafter, the controller resumes normal operation.

Two-position Valve Operation

For two position valves, one binary output drives the valve
open for N.C. actuators or drives the valve closed for N.O.
actuators. When power is removed the valve moves back
to its original position. (Closed for N.C. and open for N.O.)
1.0 to 4.6 Cv and PIC valves are capacitor discharge
return. 7.4 and 10.0 Cv valves are spring return. The
controller will cycle the valve fully open or closed based on
heating or cooling requirements.

Modulating Outdoor/Return Air

Damper

The controller operates the modulating outdoor/return air
dampers based on the following:
• Occupancy mode
• Outdoor air temperature (communicated or hard wired
sensor)
• Setpoint
• Zone temperature
• Discharge air temperature
• Discharge air temperature setpoint
The minimum position for an outdoor air damper is
configurable using the Tracer
occupied mode and occupied standby mode and for low-
speed fan operation. A controller can receive a BAS-
communicated outdoor air damper minimum position.
A BAS-communicated minimum position setpoint has
priority over all locally configured setpoints. When a
communicated minimum position setpoint is not present,
the controller uses the configured minimum position for low
fan speed whenever the fan is running at low speed,
regardless of the occupancy state. Refer to
111 and Table 37, p. 111 for more information about how
the controller determines the position of the modulating
outdoor air damper.
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TU service tool for both
Table 36, p.
BCX-SVX002A-EN