Carrier VVT Zone II Installation And Startup Manual

Also see for VVT Zone: Installation and startup guide

Contents

Sequence of operationVVT Zone II Controller CARRIER CORPORATION ©2019Installation and Start-up Guide All rights reserved49Fan Heat Off Delay – For fan-powered terminals, the controller has a configurable Fan Off Delay. After the heatingcoil de-energizes, the fan continues to run for the length of the delay to deliver to the zone any heat stored in thecoil. The default delay of 2 minutes is optimal for ducted hot water coils. For ducted electric heat coils, thenominal delay is approximately 1 minute. For baseboard and non-ducted heat, the delay should be set at 0.This feature applies to parallel fan terminals in both occupied and unoccupied mode and series fan terminals inthe unoccupied mode if the air source fan is off.Demand control ventilation (DCV) and dehumidification using optionalsensorsThe VVT Zone II’s RH/CO2 input supports an optional CO2 sensor or Relative Humidity (RH) sensor. The sensor canhave a 5-volt maximum output. The range is configurable as either 0–5 or 1–5 volts (1–5 volt supports 4–20 mAsensors with a 250 ohm resistor). The controller's low and high sensor input configuration allows for a wide rangeof sensors.The controller can also support both DCV and dehumidification functions, by using a system RH or CO2 sensorinput connected to another controller.NOTE If the connected sensor and/or system sensor value are used by the air source through Linkage, set theappropriate control type to Enable. If you do not need local control at the zone, set DCV Max Vent Airflow orMaximum RH Override Airflow to 0.Demand Control Ventilation (DCV) – Requires CO2 sensorThe zone controller monitors the CO2 sensor and can override the temperature control to respond to increasingCO2 levels when the zone is occupied. If the sensor’s value exceeds the DCV Start Ctrl Setpoint and the air sourceis in cooling or ventilation mode, the controller increases airflow to the zone at a base rate defined by ASHRAE,and then proportionally increases ventilation if the CO2 level continues to increase. If the sensor's value exceedsthe DCV Max Ctrl Setpoint, the controller modulates the damper to its DCV Max Vent Damper Position.When the zone is unoccupied, the Cooling Min Damper Position and Heating Min Damper Position provide baseventilation.If the controller is configured for reheat, the heating setpoint is temporarily increased to a value halfway betweenthe heating and cooling setpoints. If the zone temperature drops below the heating setpoint, the DCV override istemporarily suspended and the damper returns to normal control until the zone temperature is satisfied.Dehumidification – Requires RH sensorThe zone controller monitors the RH sensor and can provide dehumidification if the sensor's value exceeds theOccupied RH Control Setpoint. If the zone is occupied and does not require heating, and the air source isoperating in a cooling mode and providing primary air with a sufficiently low dew point, the controller overrides thedamper control to increase airflow to the zone. During the dehumidification mode, the heating setpoint istemporarily increased to a value halfway between the heating and cooling setpoints to prevent overcooling thezone. The controller uses a PID control loop to provide dehumidification. The controller has a Maximum RHOverride Airflow setting to prevent excessive airflow during dehumidification.NOTE If both control functions are enabled, the zone will control to the greatest calculated damper position of thethree values (temperature, RH, or IAQ).