Heat Cool Modes; Heat; Cool; Fan Only - Trane Symbio 700 Controller Application Manual

Heat Cool Modes

Heat Cool Mode Status reports the unit mode of operation. The Symbio™ 700 can receive mode inputs
from different external and local input sources that are arbitrated; however, the control active operating
mode represents the capacity being delivered to the building and reported via Heat Cool Mode Status.
The following modes of operation are supported. All other, unsupported modes are managed as an Auto
mode request.

Heat

In this mode, the controls provide heating capacity per heat type installed, heat setpoint, and occupancy.
Application requirements such as full or modulating air flow are also considered in heating mode. All
forms of cooling capacity are effectively disabled.
If Heat is the requested mode when the unit does not have heat capacity configured or heat is disabled,
Heat is reported as Heat Cool Mode Status. If the unit cannot provide heat, the supply fan is enabled to
operate (as configured) to provide ventilation during occupied modes of operation.

Cool

Cool mode is reported when the control objective is to provide cooling to maintain building comfort.
Direct expansion cooling is the primary cooling source. Cool mode is also reported when Economizer
and Dehumidification cooling modes of operation are active.

Fan Only

This mode disables all forms of heating and cooling capacity but operates the fan continuously at
minimum speed or modulates to maintain duct static pressure. The outdoor air damper modulates to
damper minimum position setpoint to provide ventilation.
Fan Only is also reported in Emergency Override and Ventilation Override Modes. Heat Cool Mode
Request can also command the control into Fan Only mode.

Off

Off is the reported mode when unit operation is shutdown due to diagnostics, equipment protections,
overrides or normal unit operation when the supply fan is cycled off.

Test

When Service Test is active, Heat Cool Mode Status reports Test.

Maximum Heat

Maximum Heat is a full airflow mode of heating operation with the supply fan operating at maximum
speed. The controller does not provide maximum heat; instead, the controller provides heat capacity per
the Operating Mode and unit type.

VVDA

Variable Volume Discharge Air control units will transition to Maximum Heat operation in heating modes
(for example Occupied Heat, Morning Warm Up, Daytime Warm Up) when the installed heating capacity
requires full air flow. Maximum Heat can also be a Heat Cool Mode Request command, which Symbio™
700 will remain in the mode until the mode is released.
On the transition to Maximum Heat the Symbio 700 will reduce the supply fan to minimum speed,
energize the VAV Box Relay and wait the duration of the VAV Box Stroke Time (adjustable). The VAV
Box Stroke Time allows the VAV boxes in the system to open. The supply fan speed will then increase to
100% or the maximum speed subject to high duct static pressure limit. Once the supply fan reaches its
allowed maximum speed, Symbio 700 will enable heating capacity control to Discharge Air Heating
Setpoint Active. Ventilation is managed per the operating mode
The transition from Maximum Heat back to modulating air flow control modes is as follows:
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