Controls VAV and CV
function and the supply fan. The air handler unit will cycle through the evening as heating/cooling (if enabled) is required in the space. When the time clock switches from night setback to occupied mode, all heating/cooling functions begin normal operation.
When using the night setback options with a VAV heating/cooling air handler, airflow must be maintained through the air handler unit. This can be accomplished by electrically tying the VAV boxes to the VAV Box output relay contacts on the Rooftop Module (RTM) or by using changeover thermostats. Either of these methods will assure adequate airflow through the unit and satisfactory temperature control of the building.
Occupied/Unoccupied input on the RTM
This input accepts a field supplied switch or contacts closure such as a time clock.
Trane Tracer™ or BAS System
The Trane Tracer System or a 3rd party BAS (with LCI module) can control the Occupied/Unoccupied status of the air handler.
Timed Override Activation -
ICS
This function is operational when the RTM is selected as the Zone Temperature Sensor source at the Human Interface Panel. When this function is initiated by the push of a override button on the ICS sensor, the Tracer will switch the unit to the Occupied mode. Unit operation (Occupied mode) during timed override is terminated by a signal from Tracer.
Timed Override Activation - Non-ICS
This function is active whenever the RTM is selected as the Zone Temperature Sensor source at the Human Interface Panel. When this function is initiated by the push of an override button on the zone sensor, the unit will switch to the Occupied mode. Automatic Cancellation of the Timed Override Mode occurs after three hours of operation.
Comparative Enthalpy Control of Economizer
An optional Comparative Enthalpy system is used to control the operation of the economizer, and measures the temperature and humidity of both return air and outside air to determine which source has lower enthalpy. This system allows true comparison of outdoor air and return air enthalpy by measurement of outdoor air and return air temperatures and humidities.
Reference Enthalpy Control of Economizer
The optional reference enthalpy compares outdoor air temperature and humidity to the economizer enthalpy control setpoint. If outdoor air temperature and humidity are below the economizer enthalpy control setpoint, the economizer will operate freely. This system provides more sophisticated control where outdoor air humidity levels may not be acceptable for building comfort and indoor air quality.
Dry Bulb Temperature Control of Economizer
The optional dry bulb system measures outdoor temperature comparing it to the economizer control temperature setpoint. If the outdoor temperature is below the economizer dry bulb temperature control setpoint, the economizer will operate freely. This system is best suited for arid regions where the humidity levels of fresh air would not be detrimental to building comfort and indoor air quality.
Emergency Stop Input
A binary input is provided on the Rooftop Module (RTM) for installation of field provided switch or contacts for immediate shutdown of all unit functions.
High Duct Temp Thermostat
Two manual reset, high temperature limit thermostats are provided. One is located in the discharge section of the unit set at 240ºF and the other in the return air section of the unit set at
135ºF. If either setpoint is reached, the air handler unit is shut down.
CO2 Control - Demand Control Ventilation (DCV)
A ventilation reset function that provides the necessary ventilation for occupants and reduces energy consumption by minimizing the outdoor air damper position (or the OA flow setpoint with TRAQs) below the Building Design Minimum, while still meeting the ASHRAE Std 62.1- 2004 ventilation requirements.
If the space CO2 level is greater than or equal to the CO2 Design Setpoint, the outdoor air damper will open to the Design Min Outdoor Air Damper (or OA Flow) Setpoint. If there is a call for economizer cooling, the outdoor air damper may be opened further to satisfy the cooling request.
If the space CO2 level is less than or equal to the CO2 Minimum Setpoint, the outdoor air damper will close to the DCV Minimum Outdoor Air Damper (or OA Flow) Setpoint.
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