Carrier RTU OPEN 11-808-427-01 Installation And Startup Manual

Also see for RTU - OPEN: Controls, Start-Up, Operation and Troubleshooting Instructions Controls, Start-Up, Operation and Troubleshooting

Contents

Sequence of Operation46 RTU OpenThe actual equation that the controller uses to calculate Optimal Start is nonlinear. An approximation of theresult is shown below.To change Optimal Start settings:1 In the navigation tree, select the equipment that you want to change.2 Click Properties page > Equipment tab > Configuration > Setpoints.Enthalpy controlYou may use an enthalpy switch to indicate the suitability of outdoor air for economizer cooling. You can useeither an outdoor air or differential enthalpy switch. A differential enthalpy switch has a sensing device in boththe outdoor and return air streams. A differential enthalpy switch indicates when outside air is cooler than thereturn air, and is available for economizer cooling. If no enthalpy switch is configured, a network point (ObjectName: oae) is available. This point is displayed in i-Vu and BACview as Enthalpy (BACnet).The sequence of operation for economizer cooling is the same with or without an enthalpy switch, except thatan enthalpy switch imposes one more validation on the suitability of outside air for economizer cooling. AnEnthalpy Status that is High disables the economizer and the outside air damper goes to its minimumposition. An Enthalpy Status that is Low enables the economizer if a call for cooling exists and the remainingpreconditions are met.Indoor Air CO2Indoor Air CO2 is controlled on rooftop equipment with an economizer. Indoor Air CO2 sequence is enabledby installing an air quality (CO2) sensor. A CO2 sensor may be terminated at the RTU Open, or a subordinatezone controller, when part of a zoned system.An outdoor air quality sensor may also be installed and terminated at the RTU Open, but it is not required.When an outdoor air quality sensor is not installed, the algorithm uses 400ppm as the fixed outdoor air CO2level.