Carrier PC 111 Operating And Troubleshooting Manual

Also see for 48FK034: Controls operation and troubleshooting

30Table 13 — VFD Set Point (Frequency Command) for Duct PressureTable 14 — Changing the VFD Set Point (Frequency Command)**Choose set point from Table 13 according to desired duct pressure or Table 15 according to desired building pressure.Modulating Power Exhaust (Option or Acces-sory) (48FK,JK and 50FK,JK Units) — The Mod-ulating Power Exhaust system will maintain space pressure bymodulating power exhaust fan no. 1 and staging power exhaustfan no. 2. Building pressure set point is established at the mod-ulating power exhaust differential pressure switch (DPS).SIZE 034-048 UNITS — The modulating power exhaust dif-ferential pressure switch is located in the auxiliary control boxmounted in the corner next to the power exhaust motor door.To gain access to this control box, remove the auxiliary controlbox cover. When replacing cover, be sure to properly secure itin order to prevent water from being drawn into the unit. SeeFig. 33.SIZE 054-104 UNITS — The modulating power exhaust dif-ferential pressure switch is mounted below the auxiliary con-trol box next to the access door labeled FILTER SECTION.See Fig. 35.DIFFERENTIAL PRESSURE SWITCH — The modulatingpower exhaust DPS has a set point range of 0.5 in. wg to–0.5 in. wg. Factory setting is +0.1 in. wg. To adjust set point,turn set point adjusting screw (see Fig. 39) clockwise todecrease set point and counterclockwise to increase set point.This switch also has an adjustable null span. The null span isthe pressure change that can be made without contacts openingor closing. It is adjustable from 0.06 in. wg to 0.14 in. wg whenset point is at minimum position (–0.5 in. wg) and 0.07 in. wgto 0.14 in. wg when set point is at maximum position(+0.5 in. wg). To adjust null span, turn null adjusting screw(Fig. 39) clockwise to decrease span and counterclockwise toincrease span. All switches leave factory with null span set atmaximum position. The smaller the null span, the closer thepressure will be maintained to desired set point.High Capacity Power Exhaust (48FM and50FM,FS Units) — The power exhaust VFD will modu-late the power exhaust fan motor no. 1 speed and stage (on/off)power exhaust fan motor no. 2 to maintain the building pres-sure. The set point for the building pressure control is set at thepower exhaust VFD using the keyboard on the front of thepower exhaust VFD enclosure. See Fig. 40.NOTE: The VFD will always provide the proper phasesequences to the power exhaust fan motor.The exhaust fan motor operates in proper rotation regardlessof the phase sequence to the unit. If, upon start-up, the outdoorfans operate backwards but the exhaust fan operates in the cor-rect direction, reverse any two leads on the main terminalblock. All fans will then operates in the correct direction.The building pressure transducer has a range of –0.5 to+0.5 in. wg. The output is a 4 to 20 mA signal, scaled to thisrange. The VFD translates the 4 to 20 mA signal to represent afrequency value over the control range of 0 to 60 Hz. SeeTable 15. The set point for duct pressure control is establishedat the power exhaust VFD keypad in terms of Hz. The factorydefault set point is 30 Hz, representing a building pressure of0.0 in. wg.DETERMINE POWER EXHAUST VFD SET POINT —The unit of measure for the building pressure set point (BPSP)at the power exhaust VFD is output frequency (Hz), represent-ing the desired BPSP (in. wg). To convert the desired BPSPinto the power exhaust VFD set point, refer to Table 15. Locatethe pressure value in the table closet to the desired BPSP forthe application and use the corresponding set point (Hz) value.If necessary, interpolation between duct static pressure valuesis permissible.ADJUST PE VFD SET POINT — To adjust the PE VFD setpoint, the PE VFD must be powered. Since it is located in theindoor section of the unit, use caution to ensure that the serviceaccess door is blocked open and will not close suddenly.Change PE VFD set point according to Table 14.PRESSURE(in. wg) VFD SET POINT (Hz) CONTROL SIGNAL(mA) PRESSURE(in. wg) VFD SET POINT(Hz) CONTROL SIGNAL(mA)0.00 0 4.0 2.00 24 10.40.25 3 4.8 2.25 27 11.20.50 6 5.6 2.50 30 12.00.75 9 6.4 2.75 33 12.81.00 12 7.2 3.00 36 13.61.25 15 8.0 3.25 39 14.41.50 18 8.8 3.50 42 15.21.75 21 9.6KEY OPERATION LED MESSAGE EXPLANATIONXX.X or OFF Standard Monitor Mode (output frequency). If drive is disabled, displaywill read “OFF”. If enabled, display will show current output frequency↓ 60.0 Pressing arrow key once will display the current frequency set point↓↑ 45.0 (flashing) Pressing up/down arrow keys changes the desired set pointFC and 45.0 (flashing) When the Read/Write key is pressed, the parameter name (FC) and the new value (45.0)will alternately flash to indicate that the new value has been stored. After 2 cycles, the display willreturn to the standard monitor mode.XX.X or OFF Standard Monitor Mode (output frequency). If drive is disabled, displaywill read “OFF”. If enabled, display will show current output frequencyREADWRITE