Carrier 50HCQ12 Installation Instructions Manual

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24If the 50HCQ unit has an economizer system andfree--cooling operation is required, a sensor representingReturn Air Temperature must also be connected(field--supplied and installed). This sensor may be a T--55Space Sensor (see Fig. 36) installed in the space or in thereturn duct, or it may be sensor PNO 33ZCSENSAT,installed in the return duct. Connect this sensor to TB3--1and TB3--3 per Fig. 37.Configure the unit for Thermostat Mode —Connect to the CCN bus using a CCN service tool andnavigate to PremierLink Configuration screen forOperating Mode. Default setting is Sensor Mode (value1). Change the value to 0 to reconfigure the controller forThermostat Mode.When the PremierLink is configured for ThermostatMode, these functions are not available: Fire Shutdown(FSD), Remote Occupied (RMTOCC), Compressor Safety(CMPSAFE), Supply Fan Status (SFS), and Filter PressureSwitch (FILTER).Economizer ControlsTo wire the return air enthalpy sensor, perform thefollowing:1. Use a 2--conductor, 18 or 20 AWG, twisted pair cableto connect the return air enthalpy sensor to the enthal-py controller.2. Connect the field--supplied RED wire to (+) spadeconnector on the return air enthalpy sensor and the(+) terminal on the enthalpy controller. Connect theBLK wire to (--) spade connector on the return air en-thalpy sensor and the (--) terminal on the enthalpycontroller.Indoor Air Quality (CO 2 sensor) —The indoor air quality sensor accessory monitors spacecarbon dioxide (CO2 ) levels. This information is used tomonitor IAQ levels. Several types of sensors are available,for wall mounting in the space or in return duct, with andwithout LCD display, and in combination with spacetemperature sensors. Sensors use infrared technology tomeasure the levels of CO2 present in the space air.The CO2 sensors are all factory set for a range of 0 to2000 ppm and a linear mA output of 4 to 20. Refer to theinstructions supplied with the CO2 sensor for electricalrequirements and terminal locations. See Fig. 41 fortypical CO2 sensor wiring schematic.To accurately monitor the quality of the air in theconditioned air space, locate the sensor near a return--airgrille (if present) so it senses the concentration of CO2leaving the space. The sensor should be mounted in alocation to avoid direct breath contact.Do not mount the IAQ sensor in drafty areas such as nearsupply ducts, open windows, fans, or over heat sources.Allow at least 3 ft (0.9 m) between the sensor and anycorner. Avoid mounting the sensor where it is influencedby the supply air; the sensor gives inaccurate readings ifthe supply air is blown directly onto the sensor or if thesupply air does not have a chance to mix with the room airbefore it is drawn into the return airstream.8 7 6 5 4 3 2 12 1H G 24 VACOR24 VDCNC ALARMRELAYCONTACTSCOMNO }0-10VDCSIG COM4-20mA++-+ -J3 J4C08635Fig. 41 -- Indoor/Outdoor Air Quality (CO 2 ) Sensor(33ZCSENCO2) -- Typical Wiring DiagramWiring the Indoor Air Quality Sensor: For each sensor,use two 2--conductor 18 AWG (American Wire Gage)twisted--pair cables (unshielded) to connect the separateisolated 24 vac power source to the sensor and to connectthe sensor to the control board terminals.To connect the sensor to the control, identify the positive(4 to 20 mA) and ground (SIG COM) terminals on thesensor. See Fig. 41. Connect the 4--20 mA terminal toterminal TB3--9 and connect the SIG COM terminal toterminal TB3--11. See Fig. 42.SEN J5-5J5-3COM911TB3TB3IAQ SensorPL24 VACC10284Fig. 42 -- Indoor CO 2 Sensor (33ZCSENCO2)ConnectionsRefer to Form 33CS--58SI, PremierLink Installation,Start--up, and Configuration Instructions, for detailedconfiguration informationOutdoor Air Quality Sensor (PNO 33ZCSENCO2 plusweatherproof enclosure) —The outdoor air CO2 sensor is designed to monitor carbondioxide (CO2 ) levels in the outside ventilation air andinterface with the ventilation damper in an HVAC system.The OAQ sensor is packaged with an outdoor cover. See50HCQD12