Carrier 39L Series Installation, Operation, And Start-up Instructions

Also see for 39L Series: Installation, Start-Up and Service Instructions

Carrier 39L Series Installation, Operation, And Start-up Instructions Manual pdf 47 page image

Duct-Mounted Relative Humidity Sensor — Theduct-mounted relative humidity sensor and mounting tem-plate are packaged and shipped inside the fan section. Thesensor is installed in either the return air ductwork or in theoutside air ductwork. If 2 relative humidity sensors are or-dered for differential enthalpy control, then the sensors mustbe installed in both the return air and outside air ducts. If thesensor is used for control of a humidifier, install the sensorin the return air duct.The PIC controller has a return air relative humidity de-fault set point of 40%.LOCATION FOR OUTSIDE AIR RELATIVE HUMIDITY— Locate the sensor where it accurately measures outdoorconditions, yet is protected from the elements. During theunoccupied (fan off) period, the sensor’s location should havea minimal effect on its readings.LOCATION FOR RETURN AIR RELATIVE HUMIDITY— Locate the sensor at least 6 in. upstream or 15 in. down-stream of a 90 degree turn in the ductwork. The best loca-tion is 15 in. downstream of the 90 degree turn of the duct.The probe should be mounted in the center of the duct. SeeFig. 33.Mount the relative humidity sensor (Fig. 34) as follows.1. Position mounting template on duct.2. Drill four 1⁄8 -in. mounting holes as indicated on thetemplate.3. Punch a 1 1 ⁄8-in. hole as indicated on the mountingtemplate.4. Mount sensor to duct using four no. 8 screws. Install 9-in.sensor probe into the 1 1⁄ 8-in. hole.Never attempt to clean or touch the sensing element withchemical solvents, as permanent damage to the sensorwill occur.Mixing Box Linkage — On units with mixing box (MXB)or filter mixing box (FMB), the actuator and linkage are fac-tory installed. The actuator is directly linked to the outdoor-air damper and holds the damper closed. No adjustment isnecessary.For shipping purposes, the secondary linkage rod con-necting the outdoor-air and return-air dampers is factory setfor a closed return-air damper.Adjust the secondary linkage as follows:1. Open the door of the MXB or FMB to access the returnair damper crankarm.NOTE: On MXB/FMB with top outdoor-air damper, itmay be necessary to remove the vertical panel holdingthe return-air damper to access the return-air dampercrankarm.2. Loosen the setscrew on the return-air damper crankarm.3. Move the damper to its full open position.4. Secure the setscrew on the return-air damper crankarm.5. Close the MXB or FMB access door.Fig. 33 — Duct-Mounted Relative HumiditySensor LocationsFig. 34 — Duct-Mounted Relative Humidity Sensor(P/N HL39ZZ002) Installation47