Carrier 48LC 04 Controls, Start-up, Operation And Troubleshooting

Also see for 48LC 05: Controls, Start-Up, Operation and Troubleshooting Service and maintenance instructions Service and maintenance instructions

Carrier 48LC 04 Controls, Start-up, Operation And Troubleshooting Manual pdf 21 page image

21ET.MX (T24TSTMX) – “T24 Test Maximum Pos” – maximumposition above which tests for a mechanically disconnectedactuator will not be performed. For example, if the actuator movesentirely within the range T24TSTMX --100 a determination ofwhether the actuator is mechanically disconnected will not bemade. This is due to the fact that at the extreme ends of the actuatormovement, a change in position may not result in a detectablechange in temperature. When the actuator stops in the range98--100% (the actuator is considered to be open), a test shall beperformed where SAT is expected to be approximately equal toOAT. If SAT is not determined to be approximately equal to OAT,a “damper not modulating” alert shall be logged.Range=50--100Default=85Economizer Actuator CommunicationThe economizer actuator used with the 48/50LC units is aMulti--Function Technology (MFT) actuator. This allows theComfortLink system to communicate with the actuator digitallyusing Belimo MP protocol. The configuration EconomizerControl Type (ConfigurationECONE.CTL) determines thecommunication method, either digital or analog, used tocommunicate between the Economizer Control Board and theeconomizer actuator.NOTE: The power to the unit must be cycled after theEconomizer Control Type (ConfigurationECONE.CTL)configuration parameter is changed.E.CTL = 1 or 2 (Digital/Position or Digital/Command)When Economizer Control Type (ConfigurationECONE.CTL) is set to 1, the Economizer Control Board willcommunicate with the economizer actuator using the digitalprotocol, from Economizer Control Board plug J7--1 to actuatorpin 5. The commanded position and the actuators actual positionare communicated back and forth between the actuator and theEconomizer Control Board. When the Economizer Control Boardand actuator first initiate communication, a Control Angle(Operating ModesECONC.ANG) is provided to theEconomizer Control Board and defines the actuator’s range ofmotion. The control angle must be greater than the Min ActuatorCtrl Angle (ConfigurationECONM.ANG). During thisdigital control, the Economizer Control Board analog 4 to 20 mAoutput will represent the actuator’s actual position when E.CTL = 1or commanded position when E.CTL =2. Because the wiring has abuilt--in 500--ohm resistor, the 4 to 20mA signal is converted to a 2to 10VDC signal at the actuator.E.CTL = 3 (Analog Control)When E.CTL is set to 3, the Economizer Control Board will NOTcommunicate with the actuator using digital MFT. It will insteadcontrol the economizer actuator directly with the 4 to 20mA analogsignal wired with the 500--ohm resistor producing a 2 to 10VDCsignal for the actuator. While in this mode, the actuator’s built--in 2to 10VDC feedback signal can be read as actual position any timebecause it is not used by the Economizer Control Board.Minimum VentilationThe economizer will open to allow ventilation when the indoor fanis running and the unit is in the occupied state. The economizerdamper position at any given time for ventilation is displayed asthe Min Position in Effect (Run StatusECONEC.MP). Thisminimum position can be effected by the indoor fan speed andindoor air quality.On Direct Drive ECM units, the economizer minimum positionwill be equal to the ECON MIN at MAX Fan Speed(ConfigurationECONMP.MX), when running High FanSpeed, ECON MIN at Low Fan Speed (ConfigurationECONMP.LO), when running Low Fan Speed, or ECONMIN at VENT Fan Speed (ConfigurationECON MP.VT)when running Ventilation Fan Speed, unless Indoor air qualityrequests something different.On Belt Drive VFD units, to maintain a constant airflow throughthe economizer, as the indoor fan speed decreases or increases, thedamper minimum position will increase or decrease, respectively.This relationship curve is shown in Fig. 6.Units can also be equipped with optional CO 2 sensors foradditional indoor air quality control. When unit is equipped with areturn duct CO 2 sensor or return duct CO 2 sensor and outside airCO 2 sensor the Economizer minimum position will be recalculatedbased on the CO 2 level of the return and/or outside air. On VFDunits the fan speed will also be used in recalculating minimumposition, as shown in Fig. 6. When the Commanded Fan Speed(F.SPD) is less than the Supply Fan Maximum Speed (FS.MX) thedamper will operate in the shaded area of Fig. 6 based on the IAQLevel (IAQ). See the Indoor Air Quality (IAQ) section (starting onpage 23) for more details on Demand Control Ventilation (DCV).Economizer Position %5001002575EC.MXMinimumFan Speed0 10050 752520Fan Speed %MP.MXMP.75MP.50MP.25AQ.MN for DCVMP.75 DCVMP.50 DCVMP.25 DCVC11544Fig. 6 -- Minimum Damper Position Curve (on units with multiple fan speeds)48/50LC